I have a function. How can I add to it an auto-completion with an available font name?
So if I type something like doSomethingWithFont Ubun<tab> it'll be completed to doSomethingWithFont Ubuntu\ Mono for example.
doSomethingWithFont () { echo $1 } _completeWithFontName () { # ???? } complete -F _completeWithFontName doSomethingWithFont You might want to use the fc_list command to list available fonts, in the format you want them to be entered.
This is how that fits into your sample code:
_completeWithFontName() { < <(fc-list -f "%{family}\n" | grep "^$2" | sort -u) mapfile -t COMPREPLY; } complete -F _completeWithFontName doSomethingWithFont Note that you should not pipe into the mapfile command: piping puts the destination command into a subshell, and you would loose the new contents of the COMPREPLY array immediately, on exit of that subshell. Redirecting < from a process substitution <(...) works better.
The -f parameter to fc-list sets the format, the simple grep command selects those font names that match the first characters entered on the command line, and the sort is for convenience. I also add a -u (unique) parameter to the sort because in this example I list only the families; each variant would appear as a duplicate, so we should sort them out.
"Ubu<tab>; the complete functionality will handle that just fine, and even add a closing quote as soon as you <tab> when your prefix has gotten unique. Without quoting, you can escape spaces: Ubuntu\ Co<tab> will complete to Ubuntu\ Condensed. Ubuntu\ Co<tab> complete to Ubuntu\ Condensed, you would have to make your function handle the backslash as an escape; the complete functionality passes it to your function in $2 as a plain backslash character followed by a space or whatever you entered. That means roughly remove unquoted backslashes, except for the 2nd of `\\` (if that ever happens in a fontname), and on output again replace spaces with escaped spaces. touch "a file" "afile" "a document" and then try to complete ls a<tab> and ls a <tab> (a space after the 'a'). Interesting things happen, that clearly have been programmed to make them happen like that for a reason. Now it's up to you to do the same for your font completion.