Using bash interactive terminal, the output of quote a is 'a' as expected. But quote doesn't work using bash -c 'quote a' or in a shell script, giving the error bash: line 1: quote: command not found. quote isn't an executable, and I failed to find quote in the bash builtins reference, so where does this command come from?
bashrc:
#
# ~/.bashrc
#
# If not running interactively, don't do anything
[[ $- != *i* ]] && return
stty -ixon
#source $HOME/.config/xdgrc
#source $HOME/.config/aliasrc
PS1='\[\033[38;2;50;255;50m\]\u\[\033[0m\]@\[\033[38;2;255;70;70m\]\h\[\033[0m\]:\w\[\033[38;2;50;255;50m\]\$\[\033[0m\]> '
quote is a helper function in /usr/share/bash-completion/bash_completion:
# This function shell-quotes the argument
quote()
{
local quoted=${1//\'/\'\\\'\'}
printf "'%s'" "$quoted"
}
I would not use it since it's only available in interactive shells when completion is enabled.
If you want to escape special characters in a script you can use ${var@Q} or printf %q instead.
$ wendys="Where's the beef?"
$ echo "${wendys@Q}"
'Where'\''s the beef?'
$ printf '%q\n' "$wendys"
Where\'s\ the\ beef\?