168 lines
3.6 KiB
Markdown
168 lines
3.6 KiB
Markdown
<h1 align="center">pure bash</h1> <p align="center">A [WIP] collection of
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pure bash alternatives to external processes.</p>
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The goal of this repository is to document known and unknown methods of
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doing various tasks using only built-in bash features. Using the snippets
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from this guide can help to remove unneeded dependencies from your scripts
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and in most cases make them that little bit faster. I came across these
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tips and discovered a few while developing
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[neofetch](https://github.com/dylanaraps/neofetch),
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[pxltrm](https://github.com/dylanaraps/pxltrm) and some other smaller
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projects.
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This repository is open to contribution. If you see something that is
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incorrectly described, buggy or outright wrong, open an issue or send a
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pull request. If you know a handy snippet that is not included in this
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list, send a pull request!
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## Table of Contents
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<!-- vim-markdown-toc GFM -->
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* [File handling](#file-handling)
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* [Get the first N lines in a file.](#get-the-first-n-lines-in-a-file)
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* [Get the last N lines in a file.](#get-the-last-n-lines-in-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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* [Strings](#strings)
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* [Get the directory name of a file path.](#get-the-directory-name-of-a-file-path)
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* [Trim quotes from a string.](#trim-quotes-from-a-string)
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* [Colors](#colors)
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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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* [Miscellaneous](#miscellaneous)
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* [Getting the terminal size (*in a script*).](#getting-the-terminal-size-in-a-script)
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* [Get the current date using `strftime`.](#get-the-current-date-using-strftime)
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<!-- vim-markdown-toc -->
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## File handling
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### Get the first N lines in a file.
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Alternative to the `head` command.
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**NOTE:** Requires `bash` 4+
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```sh
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head() {
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# Usage: head "n" "file"
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mapfile -tn "$1" line < "$2"
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printf '%s\n' "${line[@]}"
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}
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```
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### Get the last N lines in a file.
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Alternative to the `tail` command.
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**NOTE:** Requires `bash` 4+
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```sh
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tail() {
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# Usage: tail "n" "file"
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mapfile -tn 0 line < "$2"
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printf '%s\n' "${line[@]: -$1}"
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}
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```
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### Get the number of lines in a file.
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Alternative to `wc -l`.
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**NOTE:** Requires `bash` 4+
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```sh
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lines() {
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# Usage lines "file"
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mapfile -tn 0 lines < "$1"
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printf '%s\n' "${#lines[@]}"
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}
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```
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## Strings
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### Get the directory name of a file path.
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Alternative to the `dirname` command.
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```sh
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dirname() {
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# Usage: dirname "path"
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printf '%s\n' "${1%/*}/"
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}
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```
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### Trim quotes from a string.
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```sh
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trim_quotes() {
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# Usage: trim_quotes "string"
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: "${1//\'}"
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printf "%s\\n" "${_//\"}"
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}
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```
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## Colors
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### Convert a hex color to RGB
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```sh
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hex_to_rgb() {
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# Usage: hex_to_rgb "#FFFFFF"
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((r=16#${1:1:2}))
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((g=16#${1:3:2}))
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((b=16#${1:5:6}))
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printf '%s\n' "$r $g $b"
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}
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```
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### Convert an RGB color to hex.
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```sh
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rgb_to_hex() {
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# Usage: rgb_to_hex "r" "g" "b"
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printf '#%02x%02x%02x\n' "$1" "$2" "$3"
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}
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```
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## Miscellaneous
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### Getting the terminal size (*in a script*).
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This is handy when writing scripts in pure bash and `stty`/`tput` can’t be
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called.
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```sh
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get_term_size() {
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# Usage: get_term_size
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# (:;:) is a micro sleep to ensure the variables are
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# exported immediately.
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shopt -s checkwinsize; (:;:)
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printf '%s\n' "$LINES $COLUMNS"
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}
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```
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### Get the current date using `strftime`.
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Bash’s `printf` has a built-in method of getting the date which we can use
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in place of the `date` command in a lot of cases.
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**NOTE:** Requires `bash` 4+
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```sh
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date() {
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# Usage: date "format"
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# See: 'man strftime' for format.
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printf "%($1)T\\n"
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}
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```
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