180 lines
2.9 KiB
Markdown
180 lines
2.9 KiB
Markdown
# pure sh bible
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A collection of pure POSIX `sh` alternatives to external processes
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## Table of Contents
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<!-- vim-markdown-toc GFM -->
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* [STRINGS](#strings)
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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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* [Trim all white-space from string and truncate spaces](#trim-all-white-space-from-string-and-truncate-spaces)
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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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* [FILES](#files)
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* [Get the first N lines of a file](#get-the-first-n-lines-of-a-file)
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<!-- vim-markdown-toc -->
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# STRINGS
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## Strip pattern from start of string
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**Example Function:**
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```sh
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lstrip() {
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# Usage: lstrip "string" "pattern"
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printf '%s\n' "${1##$2}"
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}
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```
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**Example Usage:**
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```shell
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$ lstrip "The Quick Brown Fox" "The "
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Quick Brown Fox
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```
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## Strip pattern from end of string
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**Example Function:**
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```sh
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rstrip() {
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# Usage: rstrip "string" "pattern"
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printf '%s\n' "${1%%$2}"
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}
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```
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**Example Usage:**
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```shell
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$ rstrip "The Quick Brown Fox" " Fox"
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The Quick Brown
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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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## Check if string contains a sub-string
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**Using a case statement:**
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```shell
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case $var in
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*sub_string*)
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# Do stuff
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;;
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*sub_string2*)
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# Do more stuff
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;;
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*)
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# Else
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;;
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esac
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```
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## Check if string starts with sub-string
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**Using a case statement:**
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```shell
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case $var in
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sub_string*)
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# Do stuff
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;;
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sub_string2*)
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# Do more stuff
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;;
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*)
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# Else
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;;
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esac
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```
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## Check if string ends with sub-string
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**Using a case statement:**
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```shell
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case $var in
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*sub_string)
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# Do stuff
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;;
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*sub_string2)
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# Do more stuff
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;;
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*)
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# Else
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;;
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esac
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```
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# FILES
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## Get the first N lines of a file
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Alternative to the `head` command.
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**Example Function:**
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```sh
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head() {
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# Usage: head "n" "file"
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while read -r line; do
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[ "$i" = "$1" ] && break
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printf '%s\n' "$line"
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i=$((i+1))
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done < "$2"
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}
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```
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**Example Usage:**
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```shell
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$ head 2 ~/.bashrc
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# Prompt
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PS1='➜ '
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$ head 1 ~/.bashrc
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# Prompt
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```
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