Added build files to turn the bible into a book
This commit is contained in:
Dylan Araps
@@ -41,7 +41,6 @@ scripts and not full blown utilities.
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<br>
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<!-- CHAPTER START -->
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# Table of Contents
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<!-- vim-markdown-toc GFM -->
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@@ -155,8 +154,6 @@ scripts and not full blown utilities.
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<!-- vim-markdown-toc -->
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<!-- CHAPTER END -->
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<br>
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<!-- CHAPTER START -->
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@@ -1864,7 +1861,6 @@ command ls
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<!-- CHAPTER END -->
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<!-- CHAPTER START -->
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# Afterword
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Thanks for reading! If this bible helped you in any way and you'd like to give back, consider donating. Donations give me the time to make this the best resource possible. Can't donate? That's OK, star the repo and share it with your friends!
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@@ -15,5 +15,3 @@ chapter13.txt
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chapter14.txt
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chapter15.txt
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chapter16.txt
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chapter17.txt
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chapter18.txt
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@@ -1,115 +1,376 @@
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# Table of Contents
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# Strings
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<!-- vim-markdown-toc GFM -->
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## Trim leading and trailing white-space from string
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* [Strings](#strings)
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* [Trim leading and trailing white-space from string](#trim-leading-and-trailing-white-space-from-string)
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* [Trim all white-space from string and truncate spaces](#trim-all-white-space-from-string-and-truncate-spaces)
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* [Use regex on a string](#use-regex-on-a-string)
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* [Split a string on a delimiter](#split-a-string-on-a-delimiter)
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* [Change a string to lowercase](#change-a-string-to-lowercase)
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* [Change a string to uppercase](#change-a-string-to-uppercase)
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* [Trim quotes from a string](#trim-quotes-from-a-string)
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* [Strip all instances of pattern from string](#strip-all-instances-of-pattern-from-string)
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* [Strip first occurrence of pattern from string](#strip-first-occurrence-of-pattern-from-string)
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* [Strip pattern from start of string](#strip-pattern-from-start-of-string)
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* [Strip pattern from end of string](#strip-pattern-from-end-of-string)
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* [Check if string contains a sub-string](#check-if-string-contains-a-sub-string)
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* [Check if string starts with sub-string](#check-if-string-starts-with-sub-string)
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* [Check if string ends with sub-string](#check-if-string-ends-with-sub-string)
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* [Arrays](#arrays)
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* [Reverse an array](#reverse-an-array)
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* [Remove duplicate array elements](#remove-duplicate-array-elements)
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* [Random array element](#random-array-element)
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* [Cycle through an array](#cycle-through-an-array)
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* [Toggle between two values](#toggle-between-two-values)
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* [Loops](#loops)
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* [Loop over a range of numbers](#loop-over-a-range-of-numbers)
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* [Loop over a variable range of numbers](#loop-over-a-variable-range-of-numbers)
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* [Loop over an array](#loop-over-an-array)
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* [Loop over an array with an index](#loop-over-an-array-with-an-index)
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* [Loop over the contents of a file](#loop-over-the-contents-of-a-file)
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* [Loop over files and directories](#loop-over-files-and-directories)
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* [File handling](#file-handling)
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* [Read a file to a string](#read-a-file-to-a-string)
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* [Read a file to an array (*by line*)](#read-a-file-to-an-array-by-line)
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* [Get the first N lines of a file](#get-the-first-n-lines-of-a-file)
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* [Get the last N lines of a file](#get-the-last-n-lines-of-a-file)
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* [Get the number of lines in a file](#get-the-number-of-lines-in-a-file)
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* [Count files or directories in directory](#count-files-or-directories-in-directory)
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* [Create an empty file](#create-an-empty-file)
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* [Extract lines between two markers](#extract-lines-between-two-markers)
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* [File Paths](#file-paths)
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* [Get the directory name of a file path](#get-the-directory-name-of-a-file-path)
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* [Get the base-name of a file path](#get-the-base-name-of-a-file-path)
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* [Variables](#variables)
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* [Assign and access a variable using a variable](#assign-and-access-a-variable-using-a-variable)
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* [Escape Sequences](#escape-sequences)
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* [Text Colors](#text-colors)
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* [Text Attributes](#text-attributes)
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* [Cursor Movement](#cursor-movement)
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* [Erasing Text](#erasing-text)
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* [Parameter Expansion](#parameter-expansion)
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* [Indirection](#indirection)
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* [Replacement](#replacement)
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* [Length](#length)
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* [Expansion](#expansion)
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* [Case Modification](#case-modification)
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* [Default Value](#default-value)
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* [Brace Expansion](#brace-expansion)
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* [Ranges](#ranges)
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* [String Lists](#string-lists)
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* [Arithmetic](#arithmetic)
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* [Simpler syntax to set variables](#simpler-syntax-to-set-variables)
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* [Ternary tests](#ternary-tests)
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* [Traps](#traps)
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* [Do something on script exit](#do-something-on-script-exit)
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* [Ignore terminal interrupt (CTRL+C, SIGINT)](#ignore-terminal-interrupt-ctrlc-sigint)
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* [React to window resize.](#react-to-window-resize)
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* [Do something before every command.](#do-something-before-every-command)
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* [Do something when a shell function or a sourced file finishes executing](#do-something-when-a-shell-function-or-a-sourced-file-finishes-executing)
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* [Performance](#performance)
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* [Disable Unicode](#disable-unicode)
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* [Obsolete Syntax](#obsolete-syntax)
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* [Shebang](#shebang)
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* [Command Substitution](#command-substitution)
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* [Function Declaration](#function-declaration)
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* [Internal Variables](#internal-variables)
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* [Get the location to the `bash` binary](#get-the-location-to-the-bash-binary)
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* [Get the version of the current running `bash` process](#get-the-version-of-the-current-running-bash-process)
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* [Open the user's preferred text editor](#open-the-users-preferred-text-editor)
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* [Get the name of the current function](#get-the-name-of-the-current-function)
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* [Get the host-name of the system](#get-the-host-name-of-the-system)
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* [Get the architecture of the Operating System](#get-the-architecture-of-the-operating-system)
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* [Get the name of the Operating System / Kernel](#get-the-name-of-the-operating-system--kernel)
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* [Get the current working directory](#get-the-current-working-directory)
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* [Get the number of seconds the script has been running](#get-the-number-of-seconds-the-script-has-been-running)
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* [Get a pseudorandom integer](#get-a-pseudorandom-integer)
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* [Information about the terminal](#information-about-the-terminal)
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* [Get the terminal size in lines and columns (*from a script*)](#get-the-terminal-size-in-lines-and-columns-from-a-script)
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* [Get the terminal size in pixels](#get-the-terminal-size-in-pixels)
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* [Get the current cursor position](#get-the-current-cursor-position)
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* [Conversion](#conversion)
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* [Convert a hex color to RGB](#convert-a-hex-color-to-rgb)
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* [Convert an RGB color to hex](#convert-an-rgb-color-to-hex)
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* [Code Golf](#code-golf)
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* [Shorter `for` loop syntax](#shorter-for-loop-syntax)
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* [Shorter infinite loops](#shorter-infinite-loops)
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* [Shorter function declaration](#shorter-function-declaration)
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* [Shorter `if` syntax](#shorter-if-syntax)
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* [Simpler `case` statement to set variable](#simpler-case-statement-to-set-variable)
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* [Other](#other)
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* [Use `read` as an alternative to the `sleep` command](#use-read-as-an-alternative-to-the-sleep-command)
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* [Check if a program is in the user's PATH](#check-if-a-program-is-in-the-users-path)
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* [Get the current date using `strftime`](#get-the-current-date-using-strftime)
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* [Generate a UUID V4](#generate-a-uuid-v4)
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* [Progress bars](#progress-bars)
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* [Get the list of functions from your script](#get-the-list-of-functions-from-your-script)
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* [Bypass shell aliases](#bypass-shell-aliases)
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* [Bypass shell functions](#bypass-shell-functions)
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* [Afterword](#afterword)
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This is an alternative to `sed`, `awk`, `perl` and other tools. The
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function below works by finding all leading and trailing white-space and
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removing it from the start and end of the string. The `:` built-in is used in place of a temporary variable.
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<!-- vim-markdown-toc -->
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**Example Function:**
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```sh
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trim_string() {
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# Usage: trim_string " example string "
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: "${1#"${1%%[![:space:]]*}"}"
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: "${_%"${_##*[![:space:]]}"}"
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printf '%s\n' "$_"
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}
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```
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**Example Usage:**
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```shell
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$ trim_string " Hello, World "
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Hello, World
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$ name=" John Black "
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$ trim_string "$name"
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John Black
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```
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## Trim all white-space from string and truncate spaces
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This is an alternative to `sed`, `awk`, `perl` and other tools. The
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function below works by abusing word splitting to create a new string
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without leading/trailing white-space and with truncated spaces.
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**Example Function:**
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```sh
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# shellcheck disable=SC2086,SC2048
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trim_all() {
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# Usage: trim_all " example string "
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set -f
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set -- $*
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printf '%s\n' "$*"
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set +f
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}
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```
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**Example Usage:**
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```shell
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$ trim_all " Hello, World "
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Hello, World
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$ name=" John Black is my name. "
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$ trim_all "$name"
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John Black is my name.
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```
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## Use regex on a string
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We can use the result of `bash`'s regex matching to replace `sed` for a
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large number of use-cases.
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**CAVEAT**: This is one of the few platform dependant `bash` features.
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`bash` will use whatever regex engine is installed on the user's system.
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Stick to POSIX regex features if aiming for compatibility.
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**CAVEAT**: This example only prints the first matching group. When using
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multiple capture groups some modification is needed.
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**Example Function:**
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```sh
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regex() {
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# Usage: regex "string" "regex"
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[[ $1 =~ $2 ]] && printf '%s\n' "${BASH_REMATCH[1]}"
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}
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```
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**Example Usage:**
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```shell
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$ # Trim leading white-space.
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$ regex ' hello' '^\s*(.*)'
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hello
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$ # Validate a hex color.
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$ regex "#FFFFFF" '^(#?([a-fA-F0-9]{6}|[a-fA-F0-9]{3}))$'
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#FFFFFF
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$ # Validate a hex color (invalid).
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$ regex "red" '^(#?([a-fA-F0-9]{6}|[a-fA-F0-9]{3}))$'
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# no output (invalid)
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```
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**Example Usage in script:**
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```shell
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is_hex_color() {
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if [[ "$1" =~ ^(#?([a-fA-F0-9]{6}|[a-fA-F0-9]{3}))$ ]]; then
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printf '%s\n' "${BASH_REMATCH[1]}"
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else
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printf '%s\n' "error: $1 is an invalid color."
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return 1
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fi
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}
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read -r color
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is_hex_color "$color" || color="#FFFFFF"
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# Do stuff.
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```
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## Split a string on a delimiter
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This is an alternative to `cut`, `awk` and other tools.
|
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**Example Function:**
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```sh
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split() {
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# Usage: split "string" "delimiter"
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IFS=$'\n' read -d "" -ra arr <<< "${1//$2/$'\n'}"
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printf '%s\n' "${arr[@]}"
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}
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```
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**Example Usage:**
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```shell
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$ split "apples,oranges,pears,grapes" ","
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apples
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oranges
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pears
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grapes
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|
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$ split "1, 2, 3, 4, 5" ", "
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1
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2
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3
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4
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5
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|
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# Multi char delimiters work too!
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$ split "hello---world---my---name---is---john" "---"
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hello
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world
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my
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name
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is
|
||||
john
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```
|
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|
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## Change a string to lowercase
|
||||
|
||||
**CAVEAT:** Requires `bash` 4+
|
||||
|
||||
**Example Function:**
|
||||
|
||||
```sh
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lower() {
|
||||
# Usage: lower "string"
|
||||
printf '%s\n' "${1,,}"
|
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}
|
||||
```
|
||||
|
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**Example Usage:**
|
||||
|
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```shell
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$ lower "HELLO"
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hello
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||||
|
||||
$ lower "HeLlO"
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hello
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||||
|
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$ lower "hello"
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||||
hello
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```
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|
||||
## Change a string to uppercase
|
||||
|
||||
**CAVEAT:** Requires `bash` 4+
|
||||
|
||||
**Example Function:**
|
||||
|
||||
```sh
|
||||
upper() {
|
||||
# Usage: upper "string"
|
||||
printf '%s\n' "${1^^}"
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||||
}
|
||||
```
|
||||
|
||||
**Example Usage:**
|
||||
|
||||
```shell
|
||||
$ upper "hello"
|
||||
HELLO
|
||||
|
||||
$ upper "HeLlO"
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HELLO
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||||
|
||||
$ upper "HELLO"
|
||||
HELLO
|
||||
```
|
||||
|
||||
## Trim quotes from a string
|
||||
|
||||
**Example Function:**
|
||||
|
||||
```sh
|
||||
trim_quotes() {
|
||||
# Usage: trim_quotes "string"
|
||||
: "${1//\'}"
|
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printf '%s\n' "${_//\"}"
|
||||
}
|
||||
```
|
||||
|
||||
**Example Usage:**
|
||||
|
||||
```shell
|
||||
$ var="'Hello', \"World\""
|
||||
$ trim_quotes "$var"
|
||||
Hello, World
|
||||
```
|
||||
|
||||
## Strip all instances of pattern from string
|
||||
|
||||
**Example Function:**
|
||||
|
||||
```sh
|
||||
strip_all() {
|
||||
# Usage: strip_all "string" "pattern"
|
||||
printf '%s\n' "${1//$2}"
|
||||
}
|
||||
```
|
||||
|
||||
**Example Usage:**
|
||||
|
||||
```shell
|
||||
$ strip_all "The Quick Brown Fox" "[aeiou]"
|
||||
Th Qck Brwn Fx
|
||||
|
||||
$ strip_all "The Quick Brown Fox" "[[:space:]]"
|
||||
TheQuickBrownFox
|
||||
|
||||
$ strip_all "The Quick Brown Fox" "Quick "
|
||||
The Brown Fox
|
||||
```
|
||||
|
||||
## Strip first occurrence of pattern from string
|
||||
|
||||
**Example Function:**
|
||||
|
||||
```sh
|
||||
strip() {
|
||||
# Usage: strip "string" "pattern"
|
||||
printf '%s\n' "${1/$2}"
|
||||
}
|
||||
```
|
||||
|
||||
**Example Usage:**
|
||||
|
||||
```shell
|
||||
$ strip "The Quick Brown Fox" "[aeiou]"
|
||||
Th Quick Brown Fox
|
||||
|
||||
$ strip "The Quick Brown Fox" "[[:space:]]"
|
||||
TheQuick Brown Fox
|
||||
```
|
||||
|
||||
## Strip pattern from start of string
|
||||
|
||||
**Example Function:**
|
||||
|
||||
```sh
|
||||
lstrip() {
|
||||
# Usage: lstrip "string" "pattern"
|
||||
printf '%s\n' "${1##$2}"
|
||||
}
|
||||
```
|
||||
|
||||
**Example Usage:**
|
||||
|
||||
```shell
|
||||
$ lstrip "The Quick Brown Fox" "The "
|
||||
Quick Brown Fox
|
||||
```
|
||||
|
||||
## Strip pattern from end of string
|
||||
|
||||
**Example Function:**
|
||||
|
||||
```sh
|
||||
rstrip() {
|
||||
# Usage: rstrip "string" "pattern"
|
||||
printf '%s\n' "${1%%$2}"
|
||||
}
|
||||
```
|
||||
|
||||
**Example Usage:**
|
||||
|
||||
```shell
|
||||
$ rstrip "The Quick Brown Fox" " Fox"
|
||||
The Quick Brown
|
||||
```
|
||||
|
||||
## Check if string contains a sub-string
|
||||
|
||||
**Using a test:**
|
||||
|
||||
```shell
|
||||
if [[ "$var" == *sub_string* ]]; then
|
||||
printf '%s\n' "sub_string is in var."
|
||||
fi
|
||||
|
||||
# Inverse (substring not in string).
|
||||
if [[ "$var" != *sub_string* ]]; then
|
||||
printf '%s\n' "sub_string is not in var."
|
||||
fi
|
||||
|
||||
# This works for arrays too!
|
||||
if [[ "${arr[*]}" == *sub_string* ]]; then
|
||||
printf '%s\n' "sub_string is in array."
|
||||
fi
|
||||
```
|
||||
|
||||
**Using a case statement:**
|
||||
|
||||
```shell
|
||||
case "$var" in
|
||||
*sub_string*)
|
||||
# Do stuff
|
||||
;;
|
||||
|
||||
*sub_string2*)
|
||||
# Do more stuff
|
||||
;;
|
||||
|
||||
*)
|
||||
# Else
|
||||
;;
|
||||
esac
|
||||
```
|
||||
|
||||
## Check if string starts with sub-string
|
||||
|
||||
```shell
|
||||
if [[ "$var" == sub_string* ]]; then
|
||||
printf '%s\n' "var starts with sub_string."
|
||||
fi
|
||||
|
||||
# Inverse (var doesn't start with sub_string).
|
||||
if [[ "$var" != sub_string* ]]; then
|
||||
printf '%s\n' "var does not start with sub_string."
|
||||
fi
|
||||
```
|
||||
|
||||
## Check if string ends with sub-string
|
||||
|
||||
```shell
|
||||
if [[ "$var" == *sub_string ]]; then
|
||||
printf '%s\n' "var ends with sub_string."
|
||||
fi
|
||||
|
||||
# Inverse (var doesn't start with sub_string).
|
||||
if [[ "$var" != *sub_string ]]; then
|
||||
printf '%s\n' "var does not end with sub_string."
|
||||
fi
|
||||
```
|
||||
|
||||
<!-- CHAPTER END -->
|
||||
|
||||
|
||||
@@ -1,376 +1,130 @@
|
||||
# Strings
|
||||
# Arrays
|
||||
|
||||
## Trim leading and trailing white-space from string
|
||||
## Reverse an array
|
||||
|
||||
This is an alternative to `sed`, `awk`, `perl` and other tools. The
|
||||
function below works by finding all leading and trailing white-space and
|
||||
removing it from the start and end of the string. The `:` built-in is used in place of a temporary variable.
|
||||
Enabling `extdebug` allows access to the `BASH_ARGV` array which stores
|
||||
the current function’s arguments in reverse.
|
||||
|
||||
**Example Function:**
|
||||
|
||||
```sh
|
||||
trim_string() {
|
||||
# Usage: trim_string " example string "
|
||||
: "${1#"${1%%[![:space:]]*}"}"
|
||||
: "${_%"${_##*[![:space:]]}"}"
|
||||
printf '%s\n' "$_"
|
||||
reverse_array() {
|
||||
# Usage: reverse_array "array"
|
||||
shopt -s extdebug
|
||||
f()(printf '%s\n' "${BASH_ARGV[@]}"); f "$@"
|
||||
shopt -u extdebug
|
||||
}
|
||||
```
|
||||
|
||||
**Example Usage:**
|
||||
|
||||
```shell
|
||||
$ trim_string " Hello, World "
|
||||
Hello, World
|
||||
$ reverse_array 1 2 3 4 5
|
||||
5
|
||||
4
|
||||
3
|
||||
2
|
||||
1
|
||||
|
||||
$ name=" John Black "
|
||||
$ trim_string "$name"
|
||||
John Black
|
||||
$ arr=(red blue green)
|
||||
$ reverse_array "${arr[@]}"
|
||||
green
|
||||
blue
|
||||
red
|
||||
```
|
||||
|
||||
## Remove duplicate array elements
|
||||
|
||||
## Trim all white-space from string and truncate spaces
|
||||
Create a temporary associative array. When setting associative array
|
||||
values and a duplicate assignment occurs, bash overwrites the key. This
|
||||
allows us to effectively remove array duplicates.
|
||||
|
||||
This is an alternative to `sed`, `awk`, `perl` and other tools. The
|
||||
function below works by abusing word splitting to create a new string
|
||||
without leading/trailing white-space and with truncated spaces.
|
||||
**CAVEAT:** Requires `bash` 4+
|
||||
|
||||
**Example Function:**
|
||||
|
||||
```sh
|
||||
# shellcheck disable=SC2086,SC2048
|
||||
trim_all() {
|
||||
# Usage: trim_all " example string "
|
||||
set -f
|
||||
set -- $*
|
||||
printf '%s\n' "$*"
|
||||
set +f
|
||||
remove_array_dups() {
|
||||
# Usage: remove_array_dups "array"
|
||||
declare -A tmp_array
|
||||
|
||||
for i in "$@"; do
|
||||
[[ "$i" ]] && IFS=" " tmp_array["${i:- }"]=1
|
||||
done
|
||||
|
||||
printf '%s\n' "${!tmp_array[@]}"
|
||||
}
|
||||
```
|
||||
|
||||
**Example Usage:**
|
||||
|
||||
```shell
|
||||
$ trim_all " Hello, World "
|
||||
Hello, World
|
||||
|
||||
$ name=" John Black is my name. "
|
||||
$ trim_all "$name"
|
||||
John Black is my name.
|
||||
```
|
||||
|
||||
## Use regex on a string
|
||||
|
||||
We can use the result of `bash`'s regex matching to replace `sed` for a
|
||||
large number of use-cases.
|
||||
|
||||
**CAVEAT**: This is one of the few platform dependant `bash` features.
|
||||
`bash` will use whatever regex engine is installed on the user's system.
|
||||
Stick to POSIX regex features if aiming for compatibility.
|
||||
|
||||
**CAVEAT**: This example only prints the first matching group. When using
|
||||
multiple capture groups some modification is needed.
|
||||
|
||||
**Example Function:**
|
||||
|
||||
```sh
|
||||
regex() {
|
||||
# Usage: regex "string" "regex"
|
||||
[[ $1 =~ $2 ]] && printf '%s\n' "${BASH_REMATCH[1]}"
|
||||
}
|
||||
```
|
||||
|
||||
**Example Usage:**
|
||||
|
||||
```shell
|
||||
$ # Trim leading white-space.
|
||||
$ regex ' hello' '^\s*(.*)'
|
||||
hello
|
||||
|
||||
$ # Validate a hex color.
|
||||
$ regex "#FFFFFF" '^(#?([a-fA-F0-9]{6}|[a-fA-F0-9]{3}))$'
|
||||
#FFFFFF
|
||||
|
||||
$ # Validate a hex color (invalid).
|
||||
$ regex "red" '^(#?([a-fA-F0-9]{6}|[a-fA-F0-9]{3}))$'
|
||||
# no output (invalid)
|
||||
```
|
||||
|
||||
**Example Usage in script:**
|
||||
|
||||
```shell
|
||||
is_hex_color() {
|
||||
if [[ "$1" =~ ^(#?([a-fA-F0-9]{6}|[a-fA-F0-9]{3}))$ ]]; then
|
||||
printf '%s\n' "${BASH_REMATCH[1]}"
|
||||
else
|
||||
printf '%s\n' "error: $1 is an invalid color."
|
||||
return 1
|
||||
fi
|
||||
}
|
||||
|
||||
read -r color
|
||||
is_hex_color "$color" || color="#FFFFFF"
|
||||
|
||||
# Do stuff.
|
||||
```
|
||||
|
||||
|
||||
## Split a string on a delimiter
|
||||
|
||||
This is an alternative to `cut`, `awk` and other tools.
|
||||
|
||||
**Example Function:**
|
||||
|
||||
```sh
|
||||
split() {
|
||||
# Usage: split "string" "delimiter"
|
||||
IFS=$'\n' read -d "" -ra arr <<< "${1//$2/$'\n'}"
|
||||
printf '%s\n' "${arr[@]}"
|
||||
}
|
||||
```
|
||||
|
||||
**Example Usage:**
|
||||
|
||||
```shell
|
||||
$ split "apples,oranges,pears,grapes" ","
|
||||
apples
|
||||
oranges
|
||||
pears
|
||||
grapes
|
||||
|
||||
$ split "1, 2, 3, 4, 5" ", "
|
||||
$ remove_array_dups 1 1 2 2 3 3 3 3 3 4 4 4 4 4 5 5 5 5 5 5
|
||||
1
|
||||
2
|
||||
3
|
||||
4
|
||||
5
|
||||
|
||||
# Multi char delimiters work too!
|
||||
$ split "hello---world---my---name---is---john" "---"
|
||||
hello
|
||||
world
|
||||
my
|
||||
name
|
||||
is
|
||||
john
|
||||
$ arr=(red red green blue blue)
|
||||
$ remove_array_dups "${arr[@]}"
|
||||
red
|
||||
green
|
||||
blue
|
||||
```
|
||||
|
||||
## Change a string to lowercase
|
||||
|
||||
**CAVEAT:** Requires `bash` 4+
|
||||
## Random array element
|
||||
|
||||
**Example Function:**
|
||||
|
||||
```sh
|
||||
lower() {
|
||||
# Usage: lower "string"
|
||||
printf '%s\n' "${1,,}"
|
||||
random_array_element() {
|
||||
# Usage: random_array_element "array"
|
||||
local arr=("$@")
|
||||
printf '%s\n' "${arr[RANDOM % $#]}"
|
||||
}
|
||||
```
|
||||
|
||||
**Example Usage:**
|
||||
|
||||
```shell
|
||||
$ lower "HELLO"
|
||||
hello
|
||||
$ array=(red green blue yellow brown)
|
||||
$ random_array_element "${array[@]}"
|
||||
yellow
|
||||
|
||||
$ lower "HeLlO"
|
||||
hello
|
||||
|
||||
$ lower "hello"
|
||||
hello
|
||||
# You can also just pass multiple arguments.
|
||||
$ random_array_element 1 2 3 4 5 6 7
|
||||
3
|
||||
```
|
||||
|
||||
## Change a string to uppercase
|
||||
## Cycle through an array
|
||||
|
||||
**CAVEAT:** Requires `bash` 4+
|
||||
|
||||
**Example Function:**
|
||||
Each time the `printf` is called, the next array element is printed. When
|
||||
the print hits the last array element it starts from the first element
|
||||
again.
|
||||
|
||||
```sh
|
||||
upper() {
|
||||
# Usage: upper "string"
|
||||
printf '%s\n' "${1^^}"
|
||||
arr=(a b c d)
|
||||
|
||||
cycle() {
|
||||
printf '%s ' "${arr[${i:=0}]}"
|
||||
((i=i>=${#arr[@]}-1?0:++i))
|
||||
}
|
||||
```
|
||||
|
||||
**Example Usage:**
|
||||
|
||||
```shell
|
||||
$ upper "hello"
|
||||
HELLO
|
||||
## Toggle between two values
|
||||
|
||||
$ upper "HeLlO"
|
||||
HELLO
|
||||
|
||||
$ upper "HELLO"
|
||||
HELLO
|
||||
```
|
||||
|
||||
## Trim quotes from a string
|
||||
|
||||
**Example Function:**
|
||||
This works the same as above, this is just a different use case.
|
||||
|
||||
```sh
|
||||
trim_quotes() {
|
||||
# Usage: trim_quotes "string"
|
||||
: "${1//\'}"
|
||||
printf '%s\n' "${_//\"}"
|
||||
arr=(true false)
|
||||
|
||||
cycle() {
|
||||
printf '%s ' "${arr[${i:=0}]}"
|
||||
((i=i>=${#arr[@]}-1?0:++i))
|
||||
}
|
||||
```
|
||||
|
||||
**Example Usage:**
|
||||
|
||||
```shell
|
||||
$ var="'Hello', \"World\""
|
||||
$ trim_quotes "$var"
|
||||
Hello, World
|
||||
```
|
||||
|
||||
## Strip all instances of pattern from string
|
||||
|
||||
**Example Function:**
|
||||
|
||||
```sh
|
||||
strip_all() {
|
||||
# Usage: strip_all "string" "pattern"
|
||||
printf '%s\n' "${1//$2}"
|
||||
}
|
||||
```
|
||||
|
||||
**Example Usage:**
|
||||
|
||||
```shell
|
||||
$ strip_all "The Quick Brown Fox" "[aeiou]"
|
||||
Th Qck Brwn Fx
|
||||
|
||||
$ strip_all "The Quick Brown Fox" "[[:space:]]"
|
||||
TheQuickBrownFox
|
||||
|
||||
$ strip_all "The Quick Brown Fox" "Quick "
|
||||
The Brown Fox
|
||||
```
|
||||
|
||||
## Strip first occurrence of pattern from string
|
||||
|
||||
**Example Function:**
|
||||
|
||||
```sh
|
||||
strip() {
|
||||
# Usage: strip "string" "pattern"
|
||||
printf '%s\n' "${1/$2}"
|
||||
}
|
||||
```
|
||||
|
||||
**Example Usage:**
|
||||
|
||||
```shell
|
||||
$ strip "The Quick Brown Fox" "[aeiou]"
|
||||
Th Quick Brown Fox
|
||||
|
||||
$ strip "The Quick Brown Fox" "[[:space:]]"
|
||||
TheQuick Brown Fox
|
||||
```
|
||||
|
||||
## Strip pattern from start of string
|
||||
|
||||
**Example Function:**
|
||||
|
||||
```sh
|
||||
lstrip() {
|
||||
# Usage: lstrip "string" "pattern"
|
||||
printf '%s\n' "${1##$2}"
|
||||
}
|
||||
```
|
||||
|
||||
**Example Usage:**
|
||||
|
||||
```shell
|
||||
$ lstrip "The Quick Brown Fox" "The "
|
||||
Quick Brown Fox
|
||||
```
|
||||
|
||||
## Strip pattern from end of string
|
||||
|
||||
**Example Function:**
|
||||
|
||||
```sh
|
||||
rstrip() {
|
||||
# Usage: rstrip "string" "pattern"
|
||||
printf '%s\n' "${1%%$2}"
|
||||
}
|
||||
```
|
||||
|
||||
**Example Usage:**
|
||||
|
||||
```shell
|
||||
$ rstrip "The Quick Brown Fox" " Fox"
|
||||
The Quick Brown
|
||||
```
|
||||
|
||||
## Check if string contains a sub-string
|
||||
|
||||
**Using a test:**
|
||||
|
||||
```shell
|
||||
if [[ "$var" == *sub_string* ]]; then
|
||||
printf '%s\n' "sub_string is in var."
|
||||
fi
|
||||
|
||||
# Inverse (substring not in string).
|
||||
if [[ "$var" != *sub_string* ]]; then
|
||||
printf '%s\n' "sub_string is not in var."
|
||||
fi
|
||||
|
||||
# This works for arrays too!
|
||||
if [[ "${arr[*]}" == *sub_string* ]]; then
|
||||
printf '%s\n' "sub_string is in array."
|
||||
fi
|
||||
```
|
||||
|
||||
**Using a case statement:**
|
||||
|
||||
```shell
|
||||
case "$var" in
|
||||
*sub_string*)
|
||||
# Do stuff
|
||||
;;
|
||||
|
||||
*sub_string2*)
|
||||
# Do more stuff
|
||||
;;
|
||||
|
||||
*)
|
||||
# Else
|
||||
;;
|
||||
esac
|
||||
```
|
||||
|
||||
## Check if string starts with sub-string
|
||||
|
||||
```shell
|
||||
if [[ "$var" == sub_string* ]]; then
|
||||
printf '%s\n' "var starts with sub_string."
|
||||
fi
|
||||
|
||||
# Inverse (var doesn't start with sub_string).
|
||||
if [[ "$var" != sub_string* ]]; then
|
||||
printf '%s\n' "var does not start with sub_string."
|
||||
fi
|
||||
```
|
||||
|
||||
## Check if string ends with sub-string
|
||||
|
||||
```shell
|
||||
if [[ "$var" == *sub_string ]]; then
|
||||
printf '%s\n' "var ends with sub_string."
|
||||
fi
|
||||
|
||||
# Inverse (var doesn't start with sub_string).
|
||||
if [[ "$var" != *sub_string ]]; then
|
||||
printf '%s\n' "var does not end with sub_string."
|
||||
fi
|
||||
```
|
||||
|
||||
<!-- CHAPTER END -->
|
||||
|
||||
|
||||
@@ -1,30 +1,42 @@
|
||||
# Arithmetic
|
||||
# Traps
|
||||
|
||||
## Simpler syntax to set variables
|
||||
Traps allow you to execute code on various signals. In `pxltrm` I'm using traps to redraw the user interface on window resize. Another use case is cleaning up temporary files on script exit.
|
||||
|
||||
These `trap` lines should be added near the start of your script so any early errors are also caught.
|
||||
|
||||
**NOTE:** For a full list of signals, see `trap -l`.
|
||||
|
||||
|
||||
## Do something on script exit
|
||||
|
||||
```shell
|
||||
# Simple math
|
||||
((var=1+2))
|
||||
|
||||
# Decrement/Increment variable
|
||||
((var++))
|
||||
((var--))
|
||||
((var+=1))
|
||||
((var-=1))
|
||||
|
||||
# Using variables
|
||||
((var=var2*arr[2]))
|
||||
# Clear screen on script exit.
|
||||
trap 'printf \\e[2J\\e[H\\e[m' EXIT
|
||||
```
|
||||
|
||||
## Ternary tests
|
||||
## Ignore terminal interrupt (CTRL+C, SIGINT)
|
||||
|
||||
```shell
|
||||
# Set the value of var to var2 if var2 is greater than var.
|
||||
# var: variable to set.
|
||||
# var2>var: Condition to test.
|
||||
# ?var2: If the test succeeds.
|
||||
# :var: If the test fails.
|
||||
((var=var2>var?var2:var))
|
||||
trap '' INT
|
||||
```
|
||||
|
||||
## React to window resize.
|
||||
|
||||
```shell
|
||||
# Call a function on window resize.
|
||||
trap 'code_here' SIGWINCH
|
||||
```
|
||||
|
||||
## Do something before every command.
|
||||
|
||||
```shell
|
||||
trap 'code_here' DEBUG
|
||||
```
|
||||
|
||||
## Do something when a shell function or a sourced file finishes executing
|
||||
|
||||
```shell
|
||||
trap 'code_here' RETURN
|
||||
```
|
||||
|
||||
<!-- CHAPTER END -->
|
||||
|
||||
@@ -1,42 +1,13 @@
|
||||
# Traps
|
||||
# Performance
|
||||
|
||||
Traps allow you to execute code on various signals. In `pxltrm` I'm using traps to redraw the user interface on window resize. Another use case is cleaning up temporary files on script exit.
|
||||
## Disable Unicode
|
||||
|
||||
These `trap` lines should be added near the start of your script so any early errors are also caught.
|
||||
|
||||
**NOTE:** For a full list of signals, see `trap -l`.
|
||||
|
||||
|
||||
## Do something on script exit
|
||||
If your script doesn't require unicode, you can disable it for a speed boost. Results may vary but I've seen an improvement in Neofetch and some other smaller programs.
|
||||
|
||||
```shell
|
||||
# Clear screen on script exit.
|
||||
trap 'printf \\e[2J\\e[H\\e[m' EXIT
|
||||
```
|
||||
|
||||
## Ignore terminal interrupt (CTRL+C, SIGINT)
|
||||
|
||||
```shell
|
||||
trap '' INT
|
||||
```
|
||||
|
||||
## React to window resize.
|
||||
|
||||
```shell
|
||||
# Call a function on window resize.
|
||||
trap 'code_here' SIGWINCH
|
||||
```
|
||||
|
||||
## Do something before every command.
|
||||
|
||||
```shell
|
||||
trap 'code_here' DEBUG
|
||||
```
|
||||
|
||||
## Do something when a shell function or a sourced file finishes executing
|
||||
|
||||
```shell
|
||||
trap 'code_here' RETURN
|
||||
# Disable unicode.
|
||||
LC_ALL=C
|
||||
LANG=C
|
||||
```
|
||||
|
||||
<!-- CHAPTER END -->
|
||||
|
||||
@@ -1,13 +1,51 @@
|
||||
# Performance
|
||||
# Obsolete Syntax
|
||||
|
||||
## Disable Unicode
|
||||
## Shebang
|
||||
|
||||
If your script doesn't require unicode, you can disable it for a speed boost. Results may vary but I've seen an improvement in Neofetch and some other smaller programs.
|
||||
Use `#!/usr/bin/env bash` instead of `#!/bin/bash`.
|
||||
|
||||
- The former searches the user's `PATH` to find the `bash` binary.
|
||||
- The latter assumes it is always installed to `/bin/` which can cause issues.
|
||||
|
||||
```shell
|
||||
# Disable unicode.
|
||||
LC_ALL=C
|
||||
LANG=C
|
||||
# Right:
|
||||
|
||||
#!/usr/bin/env bash
|
||||
|
||||
# Wrong:
|
||||
|
||||
#!/bin/bash
|
||||
```
|
||||
|
||||
## Command Substitution
|
||||
|
||||
Use `$()` instead of `` ` ` ``.
|
||||
|
||||
```shell
|
||||
# Right.
|
||||
var="$(command)"
|
||||
|
||||
# Wrong.
|
||||
var=`command`
|
||||
|
||||
# $() can easily be nested whereas `` cannot.
|
||||
var="$(command "$(command)")"
|
||||
```
|
||||
|
||||
## Function Declaration
|
||||
|
||||
Don't use the `function` keyword, it reduces compatibility with older versions of `bash`.
|
||||
|
||||
```shell
|
||||
# Right.
|
||||
do_something() {
|
||||
# ...
|
||||
}
|
||||
|
||||
# Wrong.
|
||||
function do_something() {
|
||||
# ...
|
||||
}
|
||||
```
|
||||
|
||||
<!-- CHAPTER END -->
|
||||
|
||||
@@ -1,51 +1,99 @@
|
||||
# Obsolete Syntax
|
||||
# Internal Variables
|
||||
|
||||
## Shebang
|
||||
**NOTE**: This list does not include every internal variable (*You can
|
||||
help by adding a missing entry!*).
|
||||
|
||||
Use `#!/usr/bin/env bash` instead of `#!/bin/bash`.
|
||||
For a complete list, see:
|
||||
http://tldp.org/LDP/abs/html/internalvariables.html
|
||||
|
||||
- The former searches the user's `PATH` to find the `bash` binary.
|
||||
- The latter assumes it is always installed to `/bin/` which can cause issues.
|
||||
## Get the location to the `bash` binary
|
||||
|
||||
```shell
|
||||
# Right:
|
||||
|
||||
#!/usr/bin/env bash
|
||||
|
||||
# Wrong:
|
||||
|
||||
#!/bin/bash
|
||||
"$BASH"
|
||||
```
|
||||
|
||||
## Command Substitution
|
||||
|
||||
Use `$()` instead of `` ` ` ``.
|
||||
## Get the version of the current running `bash` process
|
||||
|
||||
```shell
|
||||
# Right.
|
||||
var="$(command)"
|
||||
# As a string.
|
||||
"$BASH_VERSION"
|
||||
|
||||
# Wrong.
|
||||
var=`command`
|
||||
|
||||
# $() can easily be nested whereas `` cannot.
|
||||
var="$(command "$(command)")"
|
||||
# As an array.
|
||||
"${BASH_VERSINFO[@]}"
|
||||
```
|
||||
|
||||
## Function Declaration
|
||||
|
||||
Don't use the `function` keyword, it reduces compatibility with older versions of `bash`.
|
||||
## Open the user's preferred text editor
|
||||
|
||||
```shell
|
||||
# Right.
|
||||
do_something() {
|
||||
# ...
|
||||
}
|
||||
"$EDITOR" "$file"
|
||||
|
||||
# Wrong.
|
||||
function do_something() {
|
||||
# ...
|
||||
}
|
||||
# NOTE: This variable may be empty, set a fallback value.
|
||||
"${EDITOR:-vi}" "$file"
|
||||
```
|
||||
|
||||
## Get the name of the current function
|
||||
|
||||
```shell
|
||||
# Current function.
|
||||
"${FUNCNAME[0]}"
|
||||
|
||||
# Parent function.
|
||||
"${FUNCNAME[1]}"
|
||||
|
||||
# So on and so forth.
|
||||
"${FUNCNAME[2]}"
|
||||
"${FUNCNAME[3]}"
|
||||
|
||||
# All functions including parents.
|
||||
"${FUNCNAME[@]}"
|
||||
```
|
||||
|
||||
## Get the host-name of the system
|
||||
|
||||
```shell
|
||||
"$HOSTNAME"
|
||||
|
||||
# NOTE: This variable may be empty.
|
||||
# Optionally set a fallback to the hostname command.
|
||||
"${HOSTNAME:-$(hostname)}"
|
||||
```
|
||||
|
||||
## Get the architecture of the Operating System
|
||||
|
||||
```shell
|
||||
"$HOSTTYPE"
|
||||
```
|
||||
|
||||
## Get the name of the Operating System / Kernel
|
||||
|
||||
This can be used to add conditional support for different Operating
|
||||
Systems without needing to call `uname`.
|
||||
|
||||
```shell
|
||||
"$OSTYPE"
|
||||
```
|
||||
|
||||
## Get the current working directory
|
||||
|
||||
This is an alternative to the `pwd` built-in.
|
||||
|
||||
```shell
|
||||
"$PWD"
|
||||
```
|
||||
|
||||
## Get the number of seconds the script has been running
|
||||
|
||||
```shell
|
||||
"$SECONDS"
|
||||
```
|
||||
|
||||
## Get a pseudorandom integer
|
||||
|
||||
Each time `$RANDOM` is used, a different integer between `0` and `32767` is returned. This variable should not be used for anything related to security (*this includes encryption keys etc*).
|
||||
|
||||
|
||||
```shell
|
||||
"$RANDOM"
|
||||
```
|
||||
|
||||
<!-- CHAPTER END -->
|
||||
|
||||
@@ -1,99 +1,78 @@
|
||||
# Internal Variables
|
||||
# Information about the terminal
|
||||
|
||||
**NOTE**: This list does not include every internal variable (*You can
|
||||
help by adding a missing entry!*).
|
||||
## Get the terminal size in lines and columns (*from a script*)
|
||||
|
||||
For a complete list, see:
|
||||
http://tldp.org/LDP/abs/html/internalvariables.html
|
||||
This is handy when writing scripts in pure bash and `stty`/`tput` can’t be
|
||||
called.
|
||||
|
||||
## Get the location to the `bash` binary
|
||||
**Example Function:**
|
||||
|
||||
```shell
|
||||
"$BASH"
|
||||
```sh
|
||||
get_term_size() {
|
||||
# Usage: get_term_size
|
||||
|
||||
# (:;:) is a micro sleep to ensure the variables are
|
||||
# exported immediately.
|
||||
shopt -s checkwinsize; (:;:)
|
||||
printf '%s\n' "$LINES $COLUMNS"
|
||||
}
|
||||
```
|
||||
|
||||
## Get the version of the current running `bash` process
|
||||
**Example Usage:**
|
||||
|
||||
```shell
|
||||
# As a string.
|
||||
"$BASH_VERSION"
|
||||
|
||||
# As an array.
|
||||
"${BASH_VERSINFO[@]}"
|
||||
# Output: LINES COLUMNS
|
||||
$ get_term_size
|
||||
15 55
|
||||
```
|
||||
|
||||
## Open the user's preferred text editor
|
||||
## Get the terminal size in pixels
|
||||
|
||||
```shell
|
||||
"$EDITOR" "$file"
|
||||
**CAVEAT**: This does not work in some terminal emulators.
|
||||
|
||||
# NOTE: This variable may be empty, set a fallback value.
|
||||
"${EDITOR:-vi}" "$file"
|
||||
**Example Function:**
|
||||
|
||||
```sh
|
||||
get_window_size() {
|
||||
# Usage: get_window_size
|
||||
printf '%b' "${TMUX:+\\ePtmux;\\e}\\e[14t${TMUX:+\\e\\\\}"
|
||||
IFS=';t' read -d t -t 0.05 -sra term_size
|
||||
printf '%s\n' "${term_size[1]}x${term_size[2]}"
|
||||
}
|
||||
```
|
||||
|
||||
## Get the name of the current function
|
||||
**Example Usage:**
|
||||
|
||||
```shell
|
||||
# Current function.
|
||||
"${FUNCNAME[0]}"
|
||||
# Output: WIDTHxHEIGHT
|
||||
$ get_window_size
|
||||
1200x800
|
||||
|
||||
# Parent function.
|
||||
"${FUNCNAME[1]}"
|
||||
|
||||
# So on and so forth.
|
||||
"${FUNCNAME[2]}"
|
||||
"${FUNCNAME[3]}"
|
||||
|
||||
# All functions including parents.
|
||||
"${FUNCNAME[@]}"
|
||||
# Output (fail):
|
||||
$ get_window_size
|
||||
x
|
||||
```
|
||||
|
||||
## Get the host-name of the system
|
||||
## Get the current cursor position
|
||||
|
||||
```shell
|
||||
"$HOSTNAME"
|
||||
This is useful when creating a TUI in pure bash.
|
||||
|
||||
# NOTE: This variable may be empty.
|
||||
# Optionally set a fallback to the hostname command.
|
||||
"${HOSTNAME:-$(hostname)}"
|
||||
**Example Function:**
|
||||
|
||||
```sh
|
||||
get_cursor_pos() {
|
||||
# Usage: get_cursor_pos
|
||||
IFS='[;' read -p $'\e[6n' -d R -rs _ y x _
|
||||
printf '%s\n' "$x $y"
|
||||
}
|
||||
```
|
||||
|
||||
## Get the architecture of the Operating System
|
||||
**Example Usage:**
|
||||
|
||||
```shell
|
||||
"$HOSTTYPE"
|
||||
```
|
||||
|
||||
## Get the name of the Operating System / Kernel
|
||||
|
||||
This can be used to add conditional support for different Operating
|
||||
Systems without needing to call `uname`.
|
||||
|
||||
```shell
|
||||
"$OSTYPE"
|
||||
```
|
||||
|
||||
## Get the current working directory
|
||||
|
||||
This is an alternative to the `pwd` built-in.
|
||||
|
||||
```shell
|
||||
"$PWD"
|
||||
```
|
||||
|
||||
## Get the number of seconds the script has been running
|
||||
|
||||
```shell
|
||||
"$SECONDS"
|
||||
```
|
||||
|
||||
## Get a pseudorandom integer
|
||||
|
||||
Each time `$RANDOM` is used, a different integer between `0` and `32767` is returned. This variable should not be used for anything related to security (*this includes encryption keys etc*).
|
||||
|
||||
|
||||
```shell
|
||||
"$RANDOM"
|
||||
# Output: X Y
|
||||
$ get_cursor_pos
|
||||
1 8
|
||||
```
|
||||
|
||||
<!-- CHAPTER END -->
|
||||
|
||||
@@ -1,78 +1,150 @@
|
||||
# Information about the terminal
|
||||
# Conversion
|
||||
|
||||
## Get the terminal size in lines and columns (*from a script*)
|
||||
|
||||
This is handy when writing scripts in pure bash and `stty`/`tput` can’t be
|
||||
called.
|
||||
## Convert a hex color to RGB
|
||||
|
||||
**Example Function:**
|
||||
|
||||
```sh
|
||||
get_term_size() {
|
||||
# Usage: get_term_size
|
||||
hex_to_rgb() {
|
||||
# Usage: hex_to_rgb "#FFFFFF"
|
||||
((r=16#${1:1:2}))
|
||||
((g=16#${1:3:2}))
|
||||
((b=16#${1:5:6}))
|
||||
|
||||
# (:;:) is a micro sleep to ensure the variables are
|
||||
# exported immediately.
|
||||
shopt -s checkwinsize; (:;:)
|
||||
printf '%s\n' "$LINES $COLUMNS"
|
||||
printf '%s\n' "$r $g $b"
|
||||
}
|
||||
```
|
||||
|
||||
**Example Usage:**
|
||||
|
||||
```shell
|
||||
# Output: LINES COLUMNS
|
||||
$ get_term_size
|
||||
15 55
|
||||
$ hex_to_rgb "#FFFFFF"
|
||||
255 255 255
|
||||
```
|
||||
|
||||
## Get the terminal size in pixels
|
||||
|
||||
**CAVEAT**: This does not work in some terminal emulators.
|
||||
## Convert an RGB color to hex
|
||||
|
||||
**Example Function:**
|
||||
|
||||
```sh
|
||||
get_window_size() {
|
||||
# Usage: get_window_size
|
||||
printf '%b' "${TMUX:+\\ePtmux;\\e}\\e[14t${TMUX:+\\e\\\\}"
|
||||
IFS=';t' read -d t -t 0.05 -sra term_size
|
||||
printf '%s\n' "${term_size[1]}x${term_size[2]}"
|
||||
rgb_to_hex() {
|
||||
# Usage: rgb_to_hex "r" "g" "b"
|
||||
printf '#%02x%02x%02x\n' "$1" "$2" "$3"
|
||||
}
|
||||
```
|
||||
|
||||
**Example Usage:**
|
||||
|
||||
```shell
|
||||
# Output: WIDTHxHEIGHT
|
||||
$ get_window_size
|
||||
1200x800
|
||||
|
||||
# Output (fail):
|
||||
$ get_window_size
|
||||
x
|
||||
$ rgb_to_hex "255" "255" "255"
|
||||
#FFFFFF
|
||||
```
|
||||
|
||||
## Get the current cursor position
|
||||
|
||||
This is useful when creating a TUI in pure bash.
|
||||
# Code Golf
|
||||
|
||||
**Example Function:**
|
||||
## Shorter `for` loop syntax
|
||||
|
||||
```sh
|
||||
get_cursor_pos() {
|
||||
# Usage: get_cursor_pos
|
||||
IFS='[;' read -p $'\e[6n' -d R -rs _ y x _
|
||||
printf '%s\n' "$x $y"
|
||||
```shell
|
||||
# Tiny C Style.
|
||||
for((;i++<10;)){ echo "$i";}
|
||||
|
||||
# Undocumented method.
|
||||
for i in {1..10};{ echo "$i";}
|
||||
|
||||
# Expansion.
|
||||
for i in {1..10}; do echo "$i"; done
|
||||
|
||||
# C Style.
|
||||
for((i=0;i<=10;i++)); do echo "$i"; done
|
||||
```
|
||||
|
||||
## Shorter infinite loops
|
||||
|
||||
```shell
|
||||
# Normal method
|
||||
while :; do echo hi; done
|
||||
|
||||
# Shorter
|
||||
for((;;)){ echo hi;}
|
||||
```
|
||||
|
||||
## Shorter function declaration
|
||||
|
||||
```shell
|
||||
# Normal method
|
||||
f(){ echo hi;}
|
||||
|
||||
# Using a subshell
|
||||
f()(echo hi)
|
||||
|
||||
# Using arithmetic
|
||||
# You can use this to assign integer values.
|
||||
# Example: f a=1
|
||||
# f a++
|
||||
f()(($1))
|
||||
|
||||
# Using tests, loops etc.
|
||||
# NOTE: You can also use ‘while’, ‘until’, ‘case’, ‘(())’, ‘[[]]’.
|
||||
f()if true; then echo "$1"; fi
|
||||
f()for i in "$@"; do echo "$i"; done
|
||||
```
|
||||
|
||||
## Shorter `if` syntax
|
||||
|
||||
```shell
|
||||
# One line
|
||||
# Note: The 3rd statement may run when the 1st is true
|
||||
[[ "$var" == hello ]] && echo hi || echo bye
|
||||
[[ "$var" == hello ]] && { echo hi; echo there; } || echo bye
|
||||
|
||||
# Multi line (no else, single statement)
|
||||
# Note: The exit status may not be the same as with an if statement
|
||||
[[ "$var" == hello ]] && \
|
||||
echo hi
|
||||
|
||||
# Multi line (no else)
|
||||
[[ "$var" == hello ]] && {
|
||||
echo hi
|
||||
# ...
|
||||
}
|
||||
```
|
||||
|
||||
**Example Usage:**
|
||||
## Simpler `case` statement to set variable
|
||||
|
||||
We can use the `:` builtin to avoid repeating `variable=` in a case
|
||||
statement. The `$_` variable stores the last argument of the last
|
||||
successful command. `:` always succeeds so we can abuse it to store the
|
||||
variable value.
|
||||
|
||||
```shell
|
||||
# Output: X Y
|
||||
$ get_cursor_pos
|
||||
1 8
|
||||
# Modified snippet from Neofetch.
|
||||
case "$OSTYPE" in
|
||||
"darwin"*)
|
||||
: "MacOS"
|
||||
;;
|
||||
|
||||
"linux"*)
|
||||
: "Linux"
|
||||
;;
|
||||
|
||||
*"bsd"* | "dragonfly" | "bitrig")
|
||||
: "BSD"
|
||||
;;
|
||||
|
||||
"cygwin" | "msys" | "win32")
|
||||
: "Windows"
|
||||
;;
|
||||
|
||||
*)
|
||||
printf '%s\n' "Unknown OS detected, aborting..." >&2
|
||||
exit 1
|
||||
;;
|
||||
esac
|
||||
|
||||
# Finally, set the variable.
|
||||
os="$_"
|
||||
```
|
||||
|
||||
<!-- CHAPTER END -->
|
||||
|
||||
@@ -1,150 +1,192 @@
|
||||
# Conversion
|
||||
# Other
|
||||
|
||||
## Convert a hex color to RGB
|
||||
## Use `read` as an alternative to the `sleep` command
|
||||
|
||||
I was surprised to find out `sleep` is an external command and isn't a
|
||||
built-in.
|
||||
|
||||
**CAVEAT:** Requires `bash` 4+
|
||||
|
||||
**Example Function:**
|
||||
|
||||
```sh
|
||||
hex_to_rgb() {
|
||||
# Usage: hex_to_rgb "#FFFFFF"
|
||||
((r=16#${1:1:2}))
|
||||
((g=16#${1:3:2}))
|
||||
((b=16#${1:5:6}))
|
||||
|
||||
printf '%s\n' "$r $g $b"
|
||||
read_sleep() {
|
||||
# Usage: sleep 1
|
||||
# sleep 0.2
|
||||
read -rst "${1:-1}" -N 999
|
||||
}
|
||||
```
|
||||
|
||||
**Example Usage:**
|
||||
|
||||
```shell
|
||||
$ hex_to_rgb "#FFFFFF"
|
||||
255 255 255
|
||||
read_sleep 1
|
||||
read_sleep 0.1
|
||||
read_sleep 30
|
||||
```
|
||||
|
||||
## Check if a program is in the user's PATH
|
||||
|
||||
## Convert an RGB color to hex
|
||||
```shell
|
||||
# There are 3 ways to do this and you can use either of
|
||||
# these in the same way.
|
||||
type -p executable_name &>/dev/null
|
||||
hash executable_name &>/dev/null
|
||||
command -v executable_name &>/dev/null
|
||||
|
||||
# As a test.
|
||||
if type -p executable_name &>/dev/null; then
|
||||
# Program is in PATH.
|
||||
fi
|
||||
|
||||
# Inverse.
|
||||
if ! type -p executable_name &>/dev/null; then
|
||||
# Program is not in PATH.
|
||||
fi
|
||||
|
||||
# Example (Exit early if program isn't installed).
|
||||
if ! type -p convert &>/dev/null; then
|
||||
printf '%s\n' "error: convert isn't installed, exiting..."
|
||||
exit 1
|
||||
fi
|
||||
```
|
||||
|
||||
## Get the current date using `strftime`
|
||||
|
||||
Bash’s `printf` has a built-in method of getting the date which we can use
|
||||
in place of the `date` command in a lot of cases.
|
||||
|
||||
**CAVEAT:** Requires `bash` 4+
|
||||
|
||||
**Example Function:**
|
||||
|
||||
```sh
|
||||
rgb_to_hex() {
|
||||
# Usage: rgb_to_hex "r" "g" "b"
|
||||
printf '#%02x%02x%02x\n' "$1" "$2" "$3"
|
||||
date() {
|
||||
# Usage: date "format"
|
||||
# See: 'man strftime' for format.
|
||||
printf "%($1)T\\n" "-1"
|
||||
}
|
||||
```
|
||||
|
||||
**Example Usage:**
|
||||
|
||||
```shell
|
||||
$ rgb_to_hex "255" "255" "255"
|
||||
#FFFFFF
|
||||
# Using above function.
|
||||
$ date "%a %d %b - %l:%M %p"
|
||||
Fri 15 Jun - 10:00 AM
|
||||
|
||||
# Using printf directly.
|
||||
$ printf '%(%a %d %b - %l:%M %p)T\n' "-1"
|
||||
Fri 15 Jun - 10:00 AM
|
||||
|
||||
# Assigning a variable using printf.
|
||||
$ printf -v date '%(%a %d %b - %l:%M %p)T\n' '-1'
|
||||
$ printf '%s\n' "$date"
|
||||
Fri 15 Jun - 10:00 AM
|
||||
```
|
||||
|
||||
## Generate a UUID V4
|
||||
|
||||
# Code Golf
|
||||
**Example Function:**
|
||||
|
||||
## Shorter `for` loop syntax
|
||||
```sh
|
||||
uuid() {
|
||||
# Usage: uuid
|
||||
C="89ab"
|
||||
|
||||
```shell
|
||||
# Tiny C Style.
|
||||
for((;i++<10;)){ echo "$i";}
|
||||
for ((N=0;N<16;++N)); do
|
||||
B="$((RANDOM%256))"
|
||||
|
||||
# Undocumented method.
|
||||
for i in {1..10};{ echo "$i";}
|
||||
case "$N" in
|
||||
6) printf '4%x' "$((B%16))" ;;
|
||||
8) printf '%c%x' "${C:$RANDOM%${#C}:1}" "$((B%16))" ;;
|
||||
|
||||
# Expansion.
|
||||
for i in {1..10}; do echo "$i"; done
|
||||
|
||||
# C Style.
|
||||
for((i=0;i<=10;i++)); do echo "$i"; done
|
||||
```
|
||||
|
||||
## Shorter infinite loops
|
||||
|
||||
```shell
|
||||
# Normal method
|
||||
while :; do echo hi; done
|
||||
|
||||
# Shorter
|
||||
for((;;)){ echo hi;}
|
||||
```
|
||||
|
||||
## Shorter function declaration
|
||||
|
||||
```shell
|
||||
# Normal method
|
||||
f(){ echo hi;}
|
||||
|
||||
# Using a subshell
|
||||
f()(echo hi)
|
||||
|
||||
# Using arithmetic
|
||||
# You can use this to assign integer values.
|
||||
# Example: f a=1
|
||||
# f a++
|
||||
f()(($1))
|
||||
|
||||
# Using tests, loops etc.
|
||||
# NOTE: You can also use ‘while’, ‘until’, ‘case’, ‘(())’, ‘[[]]’.
|
||||
f()if true; then echo "$1"; fi
|
||||
f()for i in "$@"; do echo "$i"; done
|
||||
```
|
||||
|
||||
## Shorter `if` syntax
|
||||
|
||||
```shell
|
||||
# One line
|
||||
# Note: The 3rd statement may run when the 1st is true
|
||||
[[ "$var" == hello ]] && echo hi || echo bye
|
||||
[[ "$var" == hello ]] && { echo hi; echo there; } || echo bye
|
||||
|
||||
# Multi line (no else, single statement)
|
||||
# Note: The exit status may not be the same as with an if statement
|
||||
[[ "$var" == hello ]] && \
|
||||
echo hi
|
||||
|
||||
# Multi line (no else)
|
||||
[[ "$var" == hello ]] && {
|
||||
echo hi
|
||||
# ...
|
||||
}
|
||||
```
|
||||
|
||||
## Simpler `case` statement to set variable
|
||||
|
||||
We can use the `:` builtin to avoid repeating `variable=` in a case
|
||||
statement. The `$_` variable stores the last argument of the last
|
||||
successful command. `:` always succeeds so we can abuse it to store the
|
||||
variable value.
|
||||
|
||||
```shell
|
||||
# Modified snippet from Neofetch.
|
||||
case "$OSTYPE" in
|
||||
"darwin"*)
|
||||
: "MacOS"
|
||||
;;
|
||||
|
||||
"linux"*)
|
||||
: "Linux"
|
||||
;;
|
||||
|
||||
*"bsd"* | "dragonfly" | "bitrig")
|
||||
: "BSD"
|
||||
;;
|
||||
|
||||
"cygwin" | "msys" | "win32")
|
||||
: "Windows"
|
||||
3|5|7|9)
|
||||
printf '%02x-' "$B"
|
||||
;;
|
||||
|
||||
*)
|
||||
printf '%s\n' "Unknown OS detected, aborting..." >&2
|
||||
exit 1
|
||||
printf '%02x' "$B"
|
||||
;;
|
||||
esac
|
||||
esac
|
||||
done
|
||||
|
||||
# Finally, set the variable.
|
||||
os="$_"
|
||||
printf '\n'
|
||||
}
|
||||
```
|
||||
|
||||
**Example Usage:**
|
||||
|
||||
```shell
|
||||
$ uuid
|
||||
d5b6c731-1310-4c24-9fe3-55d556d44374
|
||||
```
|
||||
|
||||
## Progress bars
|
||||
|
||||
This is a simple way of drawing progress bars without needing a for loop
|
||||
in the function itself.
|
||||
|
||||
**Example Function:**
|
||||
|
||||
```sh
|
||||
bar() {
|
||||
# Usage: bar 1 10
|
||||
# ^----- Elapsed Percentage (0-100).
|
||||
# ^-- Total length in chars.
|
||||
((elapsed=$1*$2/100))
|
||||
|
||||
# Create the bar with spaces.
|
||||
printf -v prog "%${elapsed}s"
|
||||
printf -v total "%$(($2-elapsed))s"
|
||||
|
||||
printf '%s\r' "[${prog// /-}${total}]"
|
||||
}
|
||||
```
|
||||
|
||||
**Example Usage:**
|
||||
|
||||
```shell
|
||||
for ((i=0;i<=100;i++)); do
|
||||
# Pure bash micro sleeps (for the example).
|
||||
(:;:) && (:;:) && (:;:) && (:;:) && (:;:)
|
||||
|
||||
# Print the bar.
|
||||
bar "$i" "10"
|
||||
done
|
||||
|
||||
printf '\n'
|
||||
```
|
||||
|
||||
## Get the list of functions from your script
|
||||
|
||||
```sh
|
||||
get_functions() {
|
||||
# Usage: get_functions
|
||||
IFS=$'\n' read -d "" -ra functions < <(declare -F)
|
||||
printf '%s\n' "${functions[@]//declare -f }"
|
||||
}
|
||||
```
|
||||
|
||||
## Bypass shell aliases
|
||||
|
||||
```shell
|
||||
# alias
|
||||
ls
|
||||
|
||||
# command
|
||||
# shellcheck disable=SC1001
|
||||
\ls
|
||||
```
|
||||
|
||||
## Bypass shell functions
|
||||
|
||||
```shell
|
||||
# function
|
||||
ls
|
||||
|
||||
# command
|
||||
command ls
|
||||
```
|
||||
|
||||
<!-- CHAPTER END -->
|
||||
|
||||
@@ -1,193 +0,0 @@
|
||||
# Other
|
||||
|
||||
## Use `read` as an alternative to the `sleep` command
|
||||
|
||||
I was surprised to find out `sleep` is an external command and isn't a
|
||||
built-in.
|
||||
|
||||
**CAVEAT:** Requires `bash` 4+
|
||||
|
||||
**Example Function:**
|
||||
|
||||
```sh
|
||||
read_sleep() {
|
||||
# Usage: sleep 1
|
||||
# sleep 0.2
|
||||
read -rst "${1:-1}" -N 999
|
||||
}
|
||||
```
|
||||
|
||||
**Example Usage:**
|
||||
|
||||
```shell
|
||||
read_sleep 1
|
||||
read_sleep 0.1
|
||||
read_sleep 30
|
||||
```
|
||||
|
||||
## Check if a program is in the user's PATH
|
||||
|
||||
```shell
|
||||
# There are 3 ways to do this and you can use either of
|
||||
# these in the same way.
|
||||
type -p executable_name &>/dev/null
|
||||
hash executable_name &>/dev/null
|
||||
command -v executable_name &>/dev/null
|
||||
|
||||
# As a test.
|
||||
if type -p executable_name &>/dev/null; then
|
||||
# Program is in PATH.
|
||||
fi
|
||||
|
||||
# Inverse.
|
||||
if ! type -p executable_name &>/dev/null; then
|
||||
# Program is not in PATH.
|
||||
fi
|
||||
|
||||
# Example (Exit early if program isn't installed).
|
||||
if ! type -p convert &>/dev/null; then
|
||||
printf '%s\n' "error: convert isn't installed, exiting..."
|
||||
exit 1
|
||||
fi
|
||||
```
|
||||
|
||||
## Get the current date using `strftime`
|
||||
|
||||
Bash’s `printf` has a built-in method of getting the date which we can use
|
||||
in place of the `date` command in a lot of cases.
|
||||
|
||||
**CAVEAT:** Requires `bash` 4+
|
||||
|
||||
**Example Function:**
|
||||
|
||||
```sh
|
||||
date() {
|
||||
# Usage: date "format"
|
||||
# See: 'man strftime' for format.
|
||||
printf "%($1)T\\n" "-1"
|
||||
}
|
||||
```
|
||||
|
||||
**Example Usage:**
|
||||
|
||||
```shell
|
||||
# Using above function.
|
||||
$ date "%a %d %b - %l:%M %p"
|
||||
Fri 15 Jun - 10:00 AM
|
||||
|
||||
# Using printf directly.
|
||||
$ printf '%(%a %d %b - %l:%M %p)T\n' "-1"
|
||||
Fri 15 Jun - 10:00 AM
|
||||
|
||||
# Assigning a variable using printf.
|
||||
$ printf -v date '%(%a %d %b - %l:%M %p)T\n' '-1'
|
||||
$ printf '%s\n' "$date"
|
||||
Fri 15 Jun - 10:00 AM
|
||||
```
|
||||
|
||||
## Generate a UUID V4
|
||||
|
||||
**Example Function:**
|
||||
|
||||
```sh
|
||||
uuid() {
|
||||
# Usage: uuid
|
||||
C="89ab"
|
||||
|
||||
for ((N=0;N<16;++N)); do
|
||||
B="$((RANDOM%256))"
|
||||
|
||||
case "$N" in
|
||||
6) printf '4%x' "$((B%16))" ;;
|
||||
8) printf '%c%x' "${C:$RANDOM%${#C}:1}" "$((B%16))" ;;
|
||||
|
||||
3|5|7|9)
|
||||
printf '%02x-' "$B"
|
||||
;;
|
||||
|
||||
*)
|
||||
printf '%02x' "$B"
|
||||
;;
|
||||
esac
|
||||
done
|
||||
|
||||
printf '\n'
|
||||
}
|
||||
```
|
||||
|
||||
**Example Usage:**
|
||||
|
||||
```shell
|
||||
$ uuid
|
||||
d5b6c731-1310-4c24-9fe3-55d556d44374
|
||||
```
|
||||
|
||||
## Progress bars
|
||||
|
||||
This is a simple way of drawing progress bars without needing a for loop
|
||||
in the function itself.
|
||||
|
||||
**Example Function:**
|
||||
|
||||
```sh
|
||||
bar() {
|
||||
# Usage: bar 1 10
|
||||
# ^----- Elapsed Percentage (0-100).
|
||||
# ^-- Total length in chars.
|
||||
((elapsed=$1*$2/100))
|
||||
|
||||
# Create the bar with spaces.
|
||||
printf -v prog "%${elapsed}s"
|
||||
printf -v total "%$(($2-elapsed))s"
|
||||
|
||||
printf '%s\r' "[${prog// /-}${total}]"
|
||||
}
|
||||
```
|
||||
|
||||
**Example Usage:**
|
||||
|
||||
```shell
|
||||
for ((i=0;i<=100;i++)); do
|
||||
# Pure bash micro sleeps (for the example).
|
||||
(:;:) && (:;:) && (:;:) && (:;:) && (:;:)
|
||||
|
||||
# Print the bar.
|
||||
bar "$i" "10"
|
||||
done
|
||||
|
||||
printf '\n'
|
||||
```
|
||||
|
||||
## Get the list of functions from your script
|
||||
|
||||
```sh
|
||||
get_functions() {
|
||||
# Usage: get_functions
|
||||
IFS=$'\n' read -d "" -ra functions < <(declare -F)
|
||||
printf '%s\n' "${functions[@]//declare -f }"
|
||||
}
|
||||
```
|
||||
|
||||
## Bypass shell aliases
|
||||
|
||||
```shell
|
||||
# alias
|
||||
ls
|
||||
|
||||
# command
|
||||
# shellcheck disable=SC1001
|
||||
\ls
|
||||
```
|
||||
|
||||
## Bypass shell functions
|
||||
|
||||
```shell
|
||||
# function
|
||||
ls
|
||||
|
||||
# command
|
||||
command ls
|
||||
```
|
||||
|
||||
<!-- CHAPTER END -->
|
||||
|
||||
@@ -1,9 +0,0 @@
|
||||
# Afterword
|
||||
|
||||
Thanks for reading! If this bible helped you in any way and you'd like to give back, consider donating. Donations give me the time to make this the best resource possible. Can't donate? That's OK, star the repo and share it with your friends!
|
||||
|
||||
<a href="https://www.paypal.com/cgi-bin/webscr?cmd=_s-xclick&hosted_button_id=V7QNJNKS3WYVS"><img src="https://img.shields.io/badge/donate-paypal-yellow.svg"></a> <a href="https://www.patreon.com/dyla"><img src="https://img.shields.io/badge/donate-patreon-yellow.svg"> </a><a href="https://liberapay.com/2211/"><img src="https://img.shields.io/badge/donate-liberapay-yellow.svg"></a>
|
||||
|
||||
|
||||
Rock on. 🤘
|
||||
|
||||
@@ -1,129 +1,94 @@
|
||||
# Arrays
|
||||
# Loops
|
||||
|
||||
## Reverse an array
|
||||
## Loop over a range of numbers
|
||||
|
||||
Enabling `extdebug` allows access to the `BASH_ARGV` array which stores
|
||||
the current function’s arguments in reverse.
|
||||
|
||||
**Example Function:**
|
||||
|
||||
```sh
|
||||
reverse_array() {
|
||||
# Usage: reverse_array "array"
|
||||
shopt -s extdebug
|
||||
f()(printf '%s\n' "${BASH_ARGV[@]}"); f "$@"
|
||||
shopt -u extdebug
|
||||
}
|
||||
```
|
||||
|
||||
**Example Usage:**
|
||||
Don't use `seq`.
|
||||
|
||||
```shell
|
||||
$ reverse_array 1 2 3 4 5
|
||||
5
|
||||
4
|
||||
3
|
||||
2
|
||||
1
|
||||
|
||||
$ arr=(red blue green)
|
||||
$ reverse_array "${arr[@]}"
|
||||
green
|
||||
blue
|
||||
red
|
||||
# Loop from 0-100 (no variable support).
|
||||
for i in {0..100}; do
|
||||
printf '%s\n' "$i"
|
||||
done
|
||||
```
|
||||
|
||||
## Remove duplicate array elements
|
||||
## Loop over a variable range of numbers
|
||||
|
||||
Create a temporary associative array. When setting associative array
|
||||
values and a duplicate assignment occurs, bash overwrites the key. This
|
||||
allows us to effectively remove array duplicates.
|
||||
|
||||
**CAVEAT:** Requires `bash` 4+
|
||||
|
||||
**Example Function:**
|
||||
|
||||
```sh
|
||||
remove_array_dups() {
|
||||
# Usage: remove_array_dups "array"
|
||||
declare -A tmp_array
|
||||
|
||||
for i in "$@"; do
|
||||
[[ "$i" ]] && IFS=" " tmp_array["${i:- }"]=1
|
||||
done
|
||||
|
||||
printf '%s\n' "${!tmp_array[@]}"
|
||||
}
|
||||
```
|
||||
|
||||
**Example Usage:**
|
||||
Don't use `seq`.
|
||||
|
||||
```shell
|
||||
$ remove_array_dups 1 1 2 2 3 3 3 3 3 4 4 4 4 4 5 5 5 5 5 5
|
||||
1
|
||||
2
|
||||
3
|
||||
4
|
||||
5
|
||||
|
||||
$ arr=(red red green blue blue)
|
||||
$ remove_array_dups "${arr[@]}"
|
||||
red
|
||||
green
|
||||
blue
|
||||
# Loop from 0-VAR.
|
||||
VAR=50
|
||||
for ((i=0;i<=VAR;i++)); do
|
||||
printf '%s\n' "$i"
|
||||
done
|
||||
```
|
||||
|
||||
## Random array element
|
||||
|
||||
**Example Function:**
|
||||
|
||||
```sh
|
||||
random_array_element() {
|
||||
# Usage: random_array_element "array"
|
||||
local arr=("$@")
|
||||
printf '%s\n' "${arr[RANDOM % $#]}"
|
||||
}
|
||||
```
|
||||
|
||||
**Example Usage:**
|
||||
## Loop over an array
|
||||
|
||||
```shell
|
||||
$ array=(red green blue yellow brown)
|
||||
$ random_array_element "${array[@]}"
|
||||
yellow
|
||||
arr=(apples oranges tomatoes)
|
||||
|
||||
# You can also just pass multiple arguments.
|
||||
$ random_array_element 1 2 3 4 5 6 7
|
||||
3
|
||||
# Just elements.
|
||||
for element in "${arr[@]}"; do
|
||||
printf '%s\n' "$element"
|
||||
done
|
||||
```
|
||||
|
||||
## Cycle through an array
|
||||
## Loop over an array with an index
|
||||
|
||||
Each time the `printf` is called, the next array element is printed. When
|
||||
the print hits the last array element it starts from the first element
|
||||
again.
|
||||
```shell
|
||||
arr=(apples oranges tomatoes)
|
||||
|
||||
```sh
|
||||
arr=(a b c d)
|
||||
# Elements and index.
|
||||
for i in "${!arr[@]}"; do
|
||||
printf '%s\n' "${arr[$i]}"
|
||||
done
|
||||
|
||||
cycle() {
|
||||
printf '%s ' "${arr[${i:=0}]}"
|
||||
((i=i>=${#arr[@]}-1?0:++i))
|
||||
}
|
||||
# Alternative method.
|
||||
for ((i=0;i<${#arr[@]};i++)); do
|
||||
printf '%s\n' "${arr[$i]}"
|
||||
done
|
||||
```
|
||||
|
||||
## Loop over the contents of a file
|
||||
|
||||
## Toggle between two values
|
||||
```shell
|
||||
while read -r line; do
|
||||
printf '%s\n' "$line"
|
||||
done < "file"
|
||||
```
|
||||
|
||||
This works the same as above, this is just a different use case.
|
||||
## Loop over files and directories
|
||||
|
||||
```sh
|
||||
arr=(true false)
|
||||
Don’t use `ls`.
|
||||
|
||||
cycle() {
|
||||
printf '%s ' "${arr[${i:=0}]}"
|
||||
((i=i>=${#arr[@]}-1?0:++i))
|
||||
}
|
||||
```shell
|
||||
# Greedy example.
|
||||
for file in *; do
|
||||
printf '%s\n' "$file"
|
||||
done
|
||||
|
||||
# PNG files in dir.
|
||||
for file in ~/Pictures/*.png; do
|
||||
printf '%s\n' "$file"
|
||||
done
|
||||
|
||||
# Iterate over directories.
|
||||
for dir in ~/Downloads/*/; do
|
||||
printf '%s\n' "$dir"
|
||||
done
|
||||
|
||||
# Brace Expansion.
|
||||
for file in /path/to/parentdir/{file1,file2,subdir/file3}; do
|
||||
printf '%s\n' "$file"
|
||||
done
|
||||
|
||||
# Iterate recursively.
|
||||
shopt -s globstar
|
||||
for file in ~/Pictures/**/*; do
|
||||
printf '%s\n' "$file"
|
||||
done
|
||||
shopt -u globstar
|
||||
```
|
||||
|
||||
<!-- CHAPTER END -->
|
||||
|
||||
@@ -1,94 +1,188 @@
|
||||
# Loops
|
||||
# File handling
|
||||
|
||||
## Loop over a range of numbers
|
||||
**CAVEAT:** `bash` doesn't handle binary data properly in versions `< 4.4`.
|
||||
|
||||
Don't use `seq`.
|
||||
## Read a file to a string
|
||||
|
||||
Alternative to the `cat` command.
|
||||
|
||||
```shell
|
||||
# Loop from 0-100 (no variable support).
|
||||
for i in {0..100}; do
|
||||
printf '%s\n' "$i"
|
||||
done
|
||||
file_data="$(<"file")"
|
||||
```
|
||||
|
||||
## Loop over a variable range of numbers
|
||||
## Read a file to an array (*by line*)
|
||||
|
||||
Don't use `seq`.
|
||||
Alternative to the `cat` command.
|
||||
|
||||
```shell
|
||||
# Loop from 0-VAR.
|
||||
VAR=50
|
||||
for ((i=0;i<=VAR;i++)); do
|
||||
printf '%s\n' "$i"
|
||||
done
|
||||
# Bash <4
|
||||
IFS=$'\n' read -d "" -ra file_data < "file"
|
||||
|
||||
# Bash 4+
|
||||
mapfile -t file_data < "file"
|
||||
```
|
||||
|
||||
## Loop over an array
|
||||
## Get the first N lines of a file
|
||||
|
||||
```shell
|
||||
arr=(apples oranges tomatoes)
|
||||
Alternative to the `head` command.
|
||||
|
||||
# Just elements.
|
||||
for element in "${arr[@]}"; do
|
||||
printf '%s\n' "$element"
|
||||
done
|
||||
**CAVEAT:** Requires `bash` 4+
|
||||
|
||||
**Example Function:**
|
||||
|
||||
```sh
|
||||
head() {
|
||||
# Usage: head "n" "file"
|
||||
mapfile -tn "$1" line < "$2"
|
||||
printf '%s\n' "${line[@]}"
|
||||
}
|
||||
```
|
||||
|
||||
## Loop over an array with an index
|
||||
**Example Usage:**
|
||||
|
||||
```shell
|
||||
arr=(apples oranges tomatoes)
|
||||
$ head 2 ~/.bashrc
|
||||
# Prompt
|
||||
PS1='➜ '
|
||||
|
||||
# Elements and index.
|
||||
for i in "${!arr[@]}"; do
|
||||
printf '%s\n' "${arr[$i]}"
|
||||
done
|
||||
|
||||
# Alternative method.
|
||||
for ((i=0;i<${#arr[@]};i++)); do
|
||||
printf '%s\n' "${arr[$i]}"
|
||||
done
|
||||
$ head 1 ~/.bashrc
|
||||
# Prompt
|
||||
```
|
||||
|
||||
## Loop over the contents of a file
|
||||
## Get the last N lines of a file
|
||||
|
||||
Alternative to the `tail` command.
|
||||
|
||||
**CAVEAT:** Requires `bash` 4+
|
||||
|
||||
**Example Function:**
|
||||
|
||||
```sh
|
||||
tail() {
|
||||
# Usage: tail "n" "file"
|
||||
mapfile -tn 0 line < "$2"
|
||||
printf '%s\n' "${line[@]: -$1}"
|
||||
}
|
||||
```
|
||||
|
||||
**Example Usage:**
|
||||
|
||||
```shell
|
||||
while read -r line; do
|
||||
$ tail 2 ~/.bashrc
|
||||
# Enable tmux.
|
||||
# [[ -z "$TMUX" ]] && exec tmux
|
||||
|
||||
$ tail 1 ~/.bashrc
|
||||
# [[ -z "$TMUX" ]] && exec tmux
|
||||
```
|
||||
|
||||
## Get the number of lines in a file
|
||||
|
||||
Alternative to `wc -l`.
|
||||
|
||||
**Example Function (bash 4):**
|
||||
|
||||
```sh
|
||||
lines() {
|
||||
# Usage: lines "file"
|
||||
mapfile -tn 0 lines < "$1"
|
||||
printf '%s\n' "${#lines[@]}"
|
||||
}
|
||||
```
|
||||
|
||||
**Example Function (bash 3):**
|
||||
|
||||
This method uses less memory than the `mapfile` method and it's more
|
||||
compatible but it's slower for bigger files.
|
||||
|
||||
```sh
|
||||
lines_loop() {
|
||||
# Usage: lines_loop "file"
|
||||
count=0
|
||||
while IFS= read -r _; do
|
||||
((count++))
|
||||
done < "$1"
|
||||
printf '%s\n' "$count"
|
||||
}
|
||||
```
|
||||
|
||||
**Example Usage:**
|
||||
|
||||
```shell
|
||||
$ lines ~/.bashrc
|
||||
48
|
||||
|
||||
$ lines_loop ~/.bashrc
|
||||
48
|
||||
```
|
||||
|
||||
## Count files or directories in directory
|
||||
|
||||
This works by passing the output of the glob as function arguments. We
|
||||
then count the arguments and print the number.
|
||||
|
||||
**Example Function:**
|
||||
|
||||
```sh
|
||||
count() {
|
||||
# Usage: count /path/to/dir/*
|
||||
# count /path/to/dir/*/
|
||||
printf '%s\n' "$#"
|
||||
}
|
||||
```
|
||||
|
||||
**Example Usage:**
|
||||
|
||||
```shell
|
||||
# Count all files in dir.
|
||||
$ count ~/Downloads/*
|
||||
232
|
||||
|
||||
# Count all dirs in dir.
|
||||
$ count ~/Downloads/*/
|
||||
45
|
||||
|
||||
# Count all jpg files in dir.
|
||||
$ count ~/Pictures/*.jpg
|
||||
64
|
||||
```
|
||||
|
||||
## Create an empty file
|
||||
|
||||
Alternative to `touch`.
|
||||
|
||||
```shell
|
||||
# Shortest.
|
||||
:> file
|
||||
|
||||
# Longer alternatives:
|
||||
echo -n > file
|
||||
printf '' > file
|
||||
```
|
||||
|
||||
## Extract lines between two markers
|
||||
|
||||
**Example Function:**
|
||||
|
||||
```sh
|
||||
extract() {
|
||||
# Usage: extract file "opening marker" "closing marker"
|
||||
while IFS=$'\n' read -r line; do
|
||||
[[ "$extract" && "$line" != "$3" ]] && \
|
||||
printf '%s\n' "$line"
|
||||
done < "file"
|
||||
|
||||
[[ "$line" == "$2" ]] && extract=1
|
||||
[[ "$line" == "$3" ]] && extract=
|
||||
done < "$1"
|
||||
}
|
||||
```
|
||||
|
||||
## Loop over files and directories
|
||||
|
||||
Don’t use `ls`.
|
||||
**Example Usage:**
|
||||
|
||||
```shell
|
||||
# Greedy example.
|
||||
for file in *; do
|
||||
printf '%s\n' "$file"
|
||||
done
|
||||
|
||||
# PNG files in dir.
|
||||
for file in ~/Pictures/*.png; do
|
||||
printf '%s\n' "$file"
|
||||
done
|
||||
|
||||
# Iterate over directories.
|
||||
for dir in ~/Downloads/*/; do
|
||||
printf '%s\n' "$dir"
|
||||
done
|
||||
|
||||
# Brace Expansion.
|
||||
for file in /path/to/parentdir/{file1,file2,subdir/file3}; do
|
||||
printf '%s\n' "$file"
|
||||
done
|
||||
|
||||
# Iterate recursively.
|
||||
shopt -s globstar
|
||||
for file in ~/Pictures/**/*; do
|
||||
printf '%s\n' "$file"
|
||||
done
|
||||
shopt -u globstar
|
||||
# Extract code blocks from MarkDown file.
|
||||
$ extract ~/projects/pure-bash/README.md '```sh' '```'
|
||||
# Output here...
|
||||
```
|
||||
|
||||
<!-- CHAPTER END -->
|
||||
|
||||
@@ -1,188 +1,50 @@
|
||||
# File handling
|
||||
# File Paths
|
||||
|
||||
**CAVEAT:** `bash` doesn't handle binary data properly in versions `< 4.4`.
|
||||
## Get the directory name of a file path
|
||||
|
||||
## Read a file to a string
|
||||
|
||||
Alternative to the `cat` command.
|
||||
|
||||
```shell
|
||||
file_data="$(<"file")"
|
||||
```
|
||||
|
||||
## Read a file to an array (*by line*)
|
||||
|
||||
Alternative to the `cat` command.
|
||||
|
||||
```shell
|
||||
# Bash <4
|
||||
IFS=$'\n' read -d "" -ra file_data < "file"
|
||||
|
||||
# Bash 4+
|
||||
mapfile -t file_data < "file"
|
||||
```
|
||||
|
||||
## Get the first N lines of a file
|
||||
|
||||
Alternative to the `head` command.
|
||||
|
||||
**CAVEAT:** Requires `bash` 4+
|
||||
Alternative to the `dirname` command.
|
||||
|
||||
**Example Function:**
|
||||
|
||||
```sh
|
||||
head() {
|
||||
# Usage: head "n" "file"
|
||||
mapfile -tn "$1" line < "$2"
|
||||
printf '%s\n' "${line[@]}"
|
||||
dirname() {
|
||||
# Usage: dirname "path"
|
||||
printf '%s\n' "${1%/*}/"
|
||||
}
|
||||
```
|
||||
|
||||
**Example Usage:**
|
||||
|
||||
```shell
|
||||
$ head 2 ~/.bashrc
|
||||
# Prompt
|
||||
PS1='➜ '
|
||||
$ dirname ~/Pictures/Wallpapers/1.jpg
|
||||
/home/black/Pictures/Wallpapers/
|
||||
|
||||
$ head 1 ~/.bashrc
|
||||
# Prompt
|
||||
$ dirname ~/Pictures/Downloads/
|
||||
/home/black/Pictures/
|
||||
```
|
||||
|
||||
## Get the last N lines of a file
|
||||
## Get the base-name of a file path
|
||||
|
||||
Alternative to the `tail` command.
|
||||
|
||||
**CAVEAT:** Requires `bash` 4+
|
||||
Alternative to the `basename` command.
|
||||
|
||||
**Example Function:**
|
||||
|
||||
```sh
|
||||
tail() {
|
||||
# Usage: tail "n" "file"
|
||||
mapfile -tn 0 line < "$2"
|
||||
printf '%s\n' "${line[@]: -$1}"
|
||||
basename() {
|
||||
# Usage: basename "path"
|
||||
: "${1%/}"
|
||||
printf '%s\n' "${_##*/}"
|
||||
}
|
||||
```
|
||||
|
||||
**Example Usage:**
|
||||
|
||||
```shell
|
||||
$ tail 2 ~/.bashrc
|
||||
# Enable tmux.
|
||||
# [[ -z "$TMUX" ]] && exec tmux
|
||||
$ basename ~/Pictures/Wallpapers/1.jpg
|
||||
1.jpg
|
||||
|
||||
$ tail 1 ~/.bashrc
|
||||
# [[ -z "$TMUX" ]] && exec tmux
|
||||
```
|
||||
|
||||
## Get the number of lines in a file
|
||||
|
||||
Alternative to `wc -l`.
|
||||
|
||||
**Example Function (bash 4):**
|
||||
|
||||
```sh
|
||||
lines() {
|
||||
# Usage: lines "file"
|
||||
mapfile -tn 0 lines < "$1"
|
||||
printf '%s\n' "${#lines[@]}"
|
||||
}
|
||||
```
|
||||
|
||||
**Example Function (bash 3):**
|
||||
|
||||
This method uses less memory than the `mapfile` method and it's more
|
||||
compatible but it's slower for bigger files.
|
||||
|
||||
```sh
|
||||
lines_loop() {
|
||||
# Usage: lines_loop "file"
|
||||
count=0
|
||||
while IFS= read -r _; do
|
||||
((count++))
|
||||
done < "$1"
|
||||
printf '%s\n' "$count"
|
||||
}
|
||||
```
|
||||
|
||||
**Example Usage:**
|
||||
|
||||
```shell
|
||||
$ lines ~/.bashrc
|
||||
48
|
||||
|
||||
$ lines_loop ~/.bashrc
|
||||
48
|
||||
```
|
||||
|
||||
## Count files or directories in directory
|
||||
|
||||
This works by passing the output of the glob as function arguments. We
|
||||
then count the arguments and print the number.
|
||||
|
||||
**Example Function:**
|
||||
|
||||
```sh
|
||||
count() {
|
||||
# Usage: count /path/to/dir/*
|
||||
# count /path/to/dir/*/
|
||||
printf '%s\n' "$#"
|
||||
}
|
||||
```
|
||||
|
||||
**Example Usage:**
|
||||
|
||||
```shell
|
||||
# Count all files in dir.
|
||||
$ count ~/Downloads/*
|
||||
232
|
||||
|
||||
# Count all dirs in dir.
|
||||
$ count ~/Downloads/*/
|
||||
45
|
||||
|
||||
# Count all jpg files in dir.
|
||||
$ count ~/Pictures/*.jpg
|
||||
64
|
||||
```
|
||||
|
||||
## Create an empty file
|
||||
|
||||
Alternative to `touch`.
|
||||
|
||||
```shell
|
||||
# Shortest.
|
||||
:> file
|
||||
|
||||
# Longer alternatives:
|
||||
echo -n > file
|
||||
printf '' > file
|
||||
```
|
||||
|
||||
## Extract lines between two markers
|
||||
|
||||
**Example Function:**
|
||||
|
||||
```sh
|
||||
extract() {
|
||||
# Usage: extract file "opening marker" "closing marker"
|
||||
while IFS=$'\n' read -r line; do
|
||||
[[ "$extract" && "$line" != "$3" ]] && \
|
||||
printf '%s\n' "$line"
|
||||
|
||||
[[ "$line" == "$2" ]] && extract=1
|
||||
[[ "$line" == "$3" ]] && extract=
|
||||
done < "$1"
|
||||
}
|
||||
```
|
||||
|
||||
**Example Usage:**
|
||||
|
||||
```shell
|
||||
# Extract code blocks from MarkDown file.
|
||||
$ extract ~/projects/pure-bash/README.md '```sh' '```'
|
||||
# Output here...
|
||||
$ basename ~/Pictures/Downloads/
|
||||
Downloads
|
||||
```
|
||||
|
||||
<!-- CHAPTER END -->
|
||||
|
||||
@@ -1,50 +1,16 @@
|
||||
# File Paths
|
||||
# Variables
|
||||
|
||||
## Get the directory name of a file path
|
||||
|
||||
Alternative to the `dirname` command.
|
||||
|
||||
**Example Function:**
|
||||
|
||||
```sh
|
||||
dirname() {
|
||||
# Usage: dirname "path"
|
||||
printf '%s\n' "${1%/*}/"
|
||||
}
|
||||
```
|
||||
|
||||
**Example Usage:**
|
||||
## Assign and access a variable using a variable
|
||||
|
||||
```shell
|
||||
$ dirname ~/Pictures/Wallpapers/1.jpg
|
||||
/home/black/Pictures/Wallpapers/
|
||||
hello_world="test"
|
||||
|
||||
$ dirname ~/Pictures/Downloads/
|
||||
/home/black/Pictures/
|
||||
```
|
||||
# Create the variable name.
|
||||
var1="world"
|
||||
var2="hello_${var1}"
|
||||
|
||||
## Get the base-name of a file path
|
||||
|
||||
Alternative to the `basename` command.
|
||||
|
||||
**Example Function:**
|
||||
|
||||
```sh
|
||||
basename() {
|
||||
# Usage: basename "path"
|
||||
: "${1%/}"
|
||||
printf '%s\n' "${_##*/}"
|
||||
}
|
||||
```
|
||||
|
||||
**Example Usage:**
|
||||
|
||||
```shell
|
||||
$ basename ~/Pictures/Wallpapers/1.jpg
|
||||
1.jpg
|
||||
|
||||
$ basename ~/Pictures/Downloads/
|
||||
Downloads
|
||||
# Print the value of the variable name stored in 'hello_$var1'.
|
||||
printf '%s\n' "${!var2}"
|
||||
```
|
||||
|
||||
<!-- CHAPTER END -->
|
||||
|
||||
@@ -1,17 +1,57 @@
|
||||
# Variables
|
||||
# Escape Sequences
|
||||
|
||||
## Assign and access a variable using a variable
|
||||
Contrary to popular belief, there's no issue in using raw escape sequences. Using `tput` just abstracts the same ANSI escape sequences. What's worse is that `tput` isn't actually portable, there are a number of different `tput` variants on different Operating Systems each with different commands (*try and run `tput setaf 3` on a FreeBSD system*). The easiest solution ends up being raw ANSI sequences.
|
||||
|
||||
```shell
|
||||
hello_world="test"
|
||||
## Text Colors
|
||||
|
||||
# Create the variable name.
|
||||
var1="world"
|
||||
var2="hello_${var1}"
|
||||
**NOTE:** Sequences requiring RGB values only work in True-Color Terminal Emulators.
|
||||
|
||||
| Sequence | What does it do? | Value |
|
||||
| -------- | ---------------- | ----- |
|
||||
| `\e[38;5;<NUM>m` | Set text foreground color. | `0-255`
|
||||
| `\e[48;5;<NUM>m` | Set text background color. | `0-255`
|
||||
| `\e[38;2;<R>;<G>;<B>m` | Set text foreground color to RGB color. | `R`, `G`, `B`
|
||||
| `\e[48;2;<R>;<G>;<B>m` | Set text background color to RGB color. | `R`, `G`, `B`
|
||||
|
||||
## Text Attributes
|
||||
|
||||
| Sequence | What does it do? |
|
||||
| -------- | ---------------- |
|
||||
| `\e[m` | Reset text formatting and colors.
|
||||
| `\e[1m` | Bold text. |
|
||||
| `\e[2m` | Faint text. |
|
||||
| `\e[3m` | Italic text. |
|
||||
| `\e[4m` | Underline text. |
|
||||
| `\e[5m` | Slow blink. |
|
||||
| `\e[7m` | Swap foreground and background colors. |
|
||||
|
||||
|
||||
## Cursor Movement
|
||||
|
||||
| Sequence | What does it do? | Value |
|
||||
| -------- | ---------------- | ----- |
|
||||
| `\e[<LINE>;<COLUMN>H` | Move cursor to absolute position. | `line`, `column`
|
||||
| `\e[H` | Move cursor to home position (`0,0`). |
|
||||
| `\e[<NUM>A` | Move cursor up N lines. | `num`
|
||||
| `\e[<NUM>B` | Move cursor down N lines. | `num`
|
||||
| `\e[<NUM>C` | Move cursor right N columns. | `num`
|
||||
| `\e[<NUM>D` | Move cursor left N columns. | `num`
|
||||
| `\e[s` | Save cursor position. |
|
||||
| `\e[u` | Restore cursor position. |
|
||||
|
||||
|
||||
## Erasing Text
|
||||
|
||||
| Sequence | What does it do? |
|
||||
| -------- | ---------------- |
|
||||
| `\e[K` | Erase from cursor position to end of line.
|
||||
| `\e[1K` | Erase from cursor position to start of line.
|
||||
| `\e[2K` | Erase the entire current line.
|
||||
| `\e[J` | Erase from the current line to the bottom of the screen.
|
||||
| `\e[1J` | Erase from the current line to the top of the screen.
|
||||
| `\e[2J` | Clear the screen.
|
||||
| `\e[2J\e[H` | Clear the screen and move cursor to `0,0`.
|
||||
|
||||
# Print the value of the variable name stored in 'hello_$var1'.
|
||||
printf '%s\n' "${!var2}"
|
||||
```
|
||||
|
||||
<!-- CHAPTER END -->
|
||||
|
||||
|
||||
@@ -1,56 +1,67 @@
|
||||
# Escape Sequences
|
||||
# Parameter Expansion
|
||||
|
||||
Contrary to popular belief, there's no issue in using raw escape sequences. Using `tput` just abstracts the same ANSI escape sequences. What's worse is that `tput` isn't actually portable, there are a number of different `tput` variants on different Operating Systems each with different commands (*try and run `tput setaf 3` on a FreeBSD system*). The easiest solution ends up being raw ANSI sequences.
|
||||
## Indirection
|
||||
|
||||
## Text Colors
|
||||
|
||||
**NOTE:** Sequences requiring RGB values only work in True-Color Terminal Emulators.
|
||||
|
||||
| Sequence | What does it do? | Value |
|
||||
| -------- | ---------------- | ----- |
|
||||
| `\e[38;5;<NUM>m` | Set text foreground color. | `0-255`
|
||||
| `\e[48;5;<NUM>m` | Set text background color. | `0-255`
|
||||
| `\e[38;2;<R>;<G>;<B>m` | Set text foreground color to RGB color. | `R`, `G`, `B`
|
||||
| `\e[48;2;<R>;<G>;<B>m` | Set text background color to RGB color. | `R`, `G`, `B`
|
||||
|
||||
## Text Attributes
|
||||
|
||||
| Sequence | What does it do? |
|
||||
| -------- | ---------------- |
|
||||
| `\e[m` | Reset text formatting and colors.
|
||||
| `\e[1m` | Bold text. |
|
||||
| `\e[2m` | Faint text. |
|
||||
| `\e[3m` | Italic text. |
|
||||
| `\e[4m` | Underline text. |
|
||||
| `\e[5m` | Slow blink. |
|
||||
| `\e[7m` | Swap foreground and background colors. |
|
||||
| Parameter | What does it do? |
|
||||
| --------- | ---------------- |
|
||||
| `${!VAR}` | Access a variable based on the value of `VAR`. See: [link](#assign-and-access-a-variable-using-a-variable)
|
||||
| `${!VAR*}` | Expand to `IFS` separated list of variable names starting with `VAR`. |
|
||||
| `${!VAR@}` | Expand to `IFS` separated list of variable names starting with `VAR`. |
|
||||
|
||||
|
||||
## Cursor Movement
|
||||
## Replacement
|
||||
|
||||
| Sequence | What does it do? | Value |
|
||||
| -------- | ---------------- | ----- |
|
||||
| `\e[<LINE>;<COLUMN>H` | Move cursor to absolute position. | `line`, `column`
|
||||
| `\e[H` | Move cursor to home position (`0,0`). |
|
||||
| `\e[<NUM>A` | Move cursor up N lines. | `num`
|
||||
| `\e[<NUM>B` | Move cursor down N lines. | `num`
|
||||
| `\e[<NUM>C` | Move cursor right N columns. | `num`
|
||||
| `\e[<NUM>D` | Move cursor left N columns. | `num`
|
||||
| `\e[s` | Save cursor position. |
|
||||
| `\e[u` | Restore cursor position. |
|
||||
| Parameter | What does it do? |
|
||||
| --------- | ---------------- |
|
||||
| `${VAR#PATTERN}` | Remove shortest match of pattern from start of string. |
|
||||
| `${VAR##PATTERN}` | Remove longest match of pattern from start of string. |
|
||||
| `${VAR%PATTERN}` | Remove shortest match of pattern from end of string. |
|
||||
| `${VAR%%PATTERN}` | Remove longest match of pattern from end of string. |
|
||||
| `${VAR/PATTERN/REPLACE}` | Replace first match with string.
|
||||
| `${VAR//PATTERN/REPLACE}` | Replace all matches with string.
|
||||
| `${VAR/PATTERN}` | Remove first match.
|
||||
| `${VAR//PATTERN}` | Remove all matches.
|
||||
|
||||
## Length
|
||||
|
||||
| Parameter | What does it do? |
|
||||
| --------- | ---------------- |
|
||||
| `${#VAR}` | Length of var in characters.
|
||||
| `${#ARR[@]}` | Length of array in elements.
|
||||
|
||||
## Expansion
|
||||
|
||||
| Parameter | What does it do? |
|
||||
| --------- | ---------------- |
|
||||
| `${VAR:OFFSET}` | Remove first `N` chars from variable.
|
||||
| `${VAR:OFFSET:LENGTH}` | Get substring from `N` character to `N` character. <br> (`${VAR:10:10}`: Get sub-string from char `10` to char `20`)
|
||||
| `${VAR:: OFFSET}` | Get first `N` chars from variable.
|
||||
| `${VAR:: -OFFSET}` | Remove last `N` chars from variable.
|
||||
| `${VAR: -OFFSET}` | Get last `N` chars from variable.
|
||||
| `${VAR:OFFSET:-OFFSET}` | Cut first `N` chars and last `N` chars. | `bash 4.2+` |
|
||||
|
||||
## Case Modification
|
||||
|
||||
| Parameter | What does it do? | CAVEAT |
|
||||
| --------- | ---------------- | ------ |
|
||||
| `${VAR^}` | Uppercase first character. | `bash 4+` |
|
||||
| `${VAR^^}` | Uppercase all characters. | `bash 4+` |
|
||||
| `${VAR,}` | Lowercase first character. | `bash 4+` |
|
||||
| `${VAR,,}` | Lowercase all characters. | `bash 4+` |
|
||||
|
||||
|
||||
## Erasing Text
|
||||
## Default Value
|
||||
|
||||
| Sequence | What does it do? |
|
||||
| -------- | ---------------- |
|
||||
| `\e[K` | Erase from cursor position to end of line.
|
||||
| `\e[1K` | Erase from cursor position to start of line.
|
||||
| `\e[2K` | Erase the entire current line.
|
||||
| `\e[J` | Erase from the current line to the bottom of the screen.
|
||||
| `\e[1J` | Erase from the current line to the top of the screen.
|
||||
| `\e[2J` | Clear the screen.
|
||||
| `\e[2J\e[H` | Clear the screen and move cursor to `0,0`.
|
||||
| Parameter | What does it do? |
|
||||
| --------- | ---------------- |
|
||||
| `${VAR:-STRING}` | If `VAR` is empty or unset, use `STRING` as it's value.
|
||||
| `${VAR-STRING}` | If `VAR` is unset, use `STRING` as it's value.
|
||||
| `${VAR:=STRING}` | If `VAR` is empty or unset, set the value of `VAR` to `STRING`.
|
||||
| `${VAR=STRING}` | If `VAR` is unset, set the value of `VAR` to `STRING`.
|
||||
| `${VAR:+STRING}` | If `VAR` isn't empty, use `STRING` as it's value.
|
||||
| `${VAR+STRING}` | If `VAR` is set, use `STRING` as it's value.
|
||||
| `${VAR:?STRING}` | Display an error if empty or unset.
|
||||
| `${VAR?STRING}` | Display an error if unset.
|
||||
|
||||
|
||||
<!-- CHAPTER END -->
|
||||
|
||||
@@ -1,68 +1,42 @@
|
||||
# Parameter Expansion
|
||||
# Brace Expansion
|
||||
|
||||
## Indirection
|
||||
## Ranges
|
||||
|
||||
| Parameter | What does it do? |
|
||||
| --------- | ---------------- |
|
||||
| `${!VAR}` | Access a variable based on the value of `VAR`. See: [link](#assign-and-access-a-variable-using-a-variable)
|
||||
| `${!VAR*}` | Expand to `IFS` separated list of variable names starting with `VAR`. |
|
||||
| `${!VAR@}` | Expand to `IFS` separated list of variable names starting with `VAR`. |
|
||||
```shell
|
||||
# Syntax: {<START>..<END>}
|
||||
|
||||
# Print numbers 1-100.
|
||||
echo {1..100}
|
||||
|
||||
## Replacement
|
||||
# Print range of floats.
|
||||
echo 1.{1..9}
|
||||
|
||||
| Parameter | What does it do? |
|
||||
| --------- | ---------------- |
|
||||
| `${VAR#PATTERN}` | Remove shortest match of pattern from start of string. |
|
||||
| `${VAR##PATTERN}` | Remove longest match of pattern from start of string. |
|
||||
| `${VAR%PATTERN}` | Remove shortest match of pattern from end of string. |
|
||||
| `${VAR%%PATTERN}` | Remove longest match of pattern from end of string. |
|
||||
| `${VAR/PATTERN/REPLACE}` | Replace first match with string.
|
||||
| `${VAR//PATTERN/REPLACE}` | Replace all matches with string.
|
||||
| `${VAR/PATTERN}` | Remove first match.
|
||||
| `${VAR//PATTERN}` | Remove all matches.
|
||||
# Print chars a-z.
|
||||
echo {a..z}
|
||||
echo {A..Z}
|
||||
|
||||
## Length
|
||||
# Nesting.
|
||||
echo {A..Z}{0..9}
|
||||
|
||||
| Parameter | What does it do? |
|
||||
| --------- | ---------------- |
|
||||
| `${#VAR}` | Length of var in characters.
|
||||
| `${#ARR[@]}` | Length of array in elements.
|
||||
# Print zero-padded numbers.
|
||||
# CAVEAT: bash 4+
|
||||
echo {01..100}
|
||||
|
||||
## Expansion
|
||||
# Change increment amount.
|
||||
# Syntax: {<START>..<END>..<INCREMENT>}
|
||||
# CAVEAT: bash 4+
|
||||
echo {1..10..2} # Increment by 2.
|
||||
```
|
||||
|
||||
| Parameter | What does it do? |
|
||||
| --------- | ---------------- |
|
||||
| `${VAR:OFFSET}` | Remove first `N` chars from variable.
|
||||
| `${VAR:OFFSET:LENGTH}` | Get substring from `N` character to `N` character. <br> (`${VAR:10:10}`: Get sub-string from char `10` to char `20`)
|
||||
| `${VAR:: OFFSET}` | Get first `N` chars from variable.
|
||||
| `${VAR:: -OFFSET}` | Remove last `N` chars from variable.
|
||||
| `${VAR: -OFFSET}` | Get last `N` chars from variable.
|
||||
| `${VAR:OFFSET:-OFFSET}` | Cut first `N` chars and last `N` chars. | `bash 4.2+` |
|
||||
## String Lists
|
||||
|
||||
## Case Modification
|
||||
|
||||
| Parameter | What does it do? | CAVEAT |
|
||||
| --------- | ---------------- | ------ |
|
||||
| `${VAR^}` | Uppercase first character. | `bash 4+` |
|
||||
| `${VAR^^}` | Uppercase all characters. | `bash 4+` |
|
||||
| `${VAR,}` | Lowercase first character. | `bash 4+` |
|
||||
| `${VAR,,}` | Lowercase all characters. | `bash 4+` |
|
||||
|
||||
|
||||
## Default Value
|
||||
|
||||
| Parameter | What does it do? |
|
||||
| --------- | ---------------- |
|
||||
| `${VAR:-STRING}` | If `VAR` is empty or unset, use `STRING` as it's value.
|
||||
| `${VAR-STRING}` | If `VAR` is unset, use `STRING` as it's value.
|
||||
| `${VAR:=STRING}` | If `VAR` is empty or unset, set the value of `VAR` to `STRING`.
|
||||
| `${VAR=STRING}` | If `VAR` is unset, set the value of `VAR` to `STRING`.
|
||||
| `${VAR:+STRING}` | If `VAR` isn't empty, use `STRING` as it's value.
|
||||
| `${VAR+STRING}` | If `VAR` is set, use `STRING` as it's value.
|
||||
| `${VAR:?STRING}` | Display an error if empty or unset.
|
||||
| `${VAR?STRING}` | Display an error if unset.
|
||||
```shell
|
||||
echo {apples,oranges,pears,grapes}
|
||||
|
||||
# Example Usage:
|
||||
# Remove dirs Movies, Music and ISOS from ~/Downloads/.
|
||||
rm -rf ~/Downloads/{Movies,Music,ISOS}
|
||||
```
|
||||
|
||||
<!-- CHAPTER END -->
|
||||
|
||||
|
||||
@@ -1,41 +1,30 @@
|
||||
# Brace Expansion
|
||||
# Arithmetic
|
||||
|
||||
## Ranges
|
||||
## Simpler syntax to set variables
|
||||
|
||||
```shell
|
||||
# Syntax: {<START>..<END>}
|
||||
# Simple math
|
||||
((var=1+2))
|
||||
|
||||
# Print numbers 1-100.
|
||||
echo {1..100}
|
||||
# Decrement/Increment variable
|
||||
((var++))
|
||||
((var--))
|
||||
((var+=1))
|
||||
((var-=1))
|
||||
|
||||
# Print range of floats.
|
||||
echo 1.{1..9}
|
||||
|
||||
# Print chars a-z.
|
||||
echo {a..z}
|
||||
echo {A..Z}
|
||||
|
||||
# Nesting.
|
||||
echo {A..Z}{0..9}
|
||||
|
||||
# Print zero-padded numbers.
|
||||
# CAVEAT: bash 4+
|
||||
echo {01..100}
|
||||
|
||||
# Change increment amount.
|
||||
# Syntax: {<START>..<END>..<INCREMENT>}
|
||||
# CAVEAT: bash 4+
|
||||
echo {1..10..2} # Increment by 2.
|
||||
# Using variables
|
||||
((var=var2*arr[2]))
|
||||
```
|
||||
|
||||
## String Lists
|
||||
## Ternary tests
|
||||
|
||||
```shell
|
||||
echo {apples,oranges,pears,grapes}
|
||||
|
||||
# Example Usage:
|
||||
# Remove dirs Movies, Music and ISOS from ~/Downloads/.
|
||||
rm -rf ~/Downloads/{Movies,Music,ISOS}
|
||||
# Set the value of var to var2 if var2 is greater than var.
|
||||
# var: variable to set.
|
||||
# var2>var: Condition to test.
|
||||
# ?var2: If the test succeeds.
|
||||
# :var: If the test fails.
|
||||
((var=var2>var?var2:var))
|
||||
```
|
||||
|
||||
<!-- CHAPTER END -->
|
||||
|
||||
Reference in New Issue
Block a user