Bash
strtolower() in Bash: Convert a String to Lowercase
A strtolower() for Bash 4 and the stock macOS Bash 3.2, why ${var,,} depends on your locale, and when declare -l, tr, awk or nocasematch fit better.
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Bash
strtoupper() in Bash: Convert a String to Uppercase
A strtoupper() that works on Bash 4+ and macOS's Bash 3.2, plus ${var^^pattern} for uppercasing only some characters and declare -u for variables.
Bash
stristr() in Bash: Case-Insensitive Substring Search
Check whether a string contains a substring regardless of case, with a Bash 4 version, a Bash 3.2 fallback using nocasematch, and a PHP-style stristr().
Bash
strstr() in Bash: Check if a String Contains a Substring
Test whether a string contains a substring in pure Bash, or get the rest of the string from the first match the way PHP's strstr() does.
Bash
dirname() in Bash: Get the Directory Part of a Path
Get the directory part of a path in pure Bash, matching coreutils dirname on trailing slashes, bare names and the root, without starting a process.
Bash
yesno() in Bash: Ask a Yes/No Question Safely
A yes/no confirmation prompt for Bash scripts that accepts any case, has an optional default and handles cron, pipes and EOF without looping forever.
Bash
basename() in Bash: Strip the Directory From a Path
Get the file name from a path with parameter expansion, matching coreutils basename on trailing slashes, "/" and suffixes, without starting a process.
Bash
ucfirst() in Bash: Uppercase the First Character
A ucfirst() for Bash 4+ and macOS's Bash 3.2, what "first character" really means, and how to get "Hello" from "hELLO" or " hello".
Bash
ucwords() in Bash: Capitalise Every Word in a String
A ucwords() for Bash that works word by word instead of char by char, preserves all whitespace, and lets you decide what counts as a word boundary.
Bash
_execq() in Bash: Run a Command Quietly and Keep Its Status
Run a command silently and test only its exit status. Why "$@" beats storing a command in a string, and what to use for pipelines.