Replace tilde with pattern substitution

Question

Normally I use the ${parameter/pattern/string} construct in bash to replace characters.

For example, ${i//(/_} replaces all ( characters with _ in $i. For illustration:

find . -depth -type d -name '*(*' -execdir bash -c 'for i; do mv "$i" "${i//(/_}"; done' _ {} +

I cannot get it to work with ~. ${i//~/_} yields the value of $i, unchanged, even if it contains tilde(s).

It's weird – it works with every single other symbol I use except a question mark. Any ideas with the tilde?

score 3 · Answer 1 · answered Jan 14 '21 at 22:17

bash(1) doesn’t clearly document the fact that, when you do

${parameter/pattern/string}

the pattern and string are subject to all the expansions that apply to plain (unquoted) words on the command line. Consider this example:

$ balance=credit
$ fire=red
$ sky=blue
$ echo "${balance/$fire/$sky}"
cblueit

Your problem, of course, is that ~ gets expanded to your home directory:

$ i=foo/home/JandPbar
$ echo "${i/~/_}"
foo_bar

So, as suggested in the comment, you need to quote/escape the ~, with "${i/'~'/_}" or "${i/\~/_}".

1 Answers1