2017-03-06 16:44:01 -0600, Eric Blake: [...] > > To reproduce run in empty directory > > > > echo "start_string_20091210.end" | grep -o > > [1-2][0][0-1][0-9][0-1][0-9][0-3][0-9] > > Underquoted. This asks the shell to perform globbing for all files that > match those patterns. Initially, none do, so the shell passes the > pattern on unchanged to grep. [...]
For completeness, that happens with most shells but not fish where [...] is not a glob operator. Also, with zsh, csh, tcsh and pre-Bourne shells, you would have had a "not found" error as the glob doesn't match any file that would have helped identify the source of problem earlier. That was /broken/ by the Bourne shell in the late seventies that instead passes the glob unexpanded to the command when it doesn't match any file. All Bourne-like shells except zsh, and rc-like shells are /broken/ in the same way. fish doesn't have the issue (for its own globs that don't include [...]). In recent versions of bash, you can do: shopt -s failglob to get the /better/ behaviour. See also https://unix.stackexchange.com/questions/204803/why-is-nullglob-not-default for more information on that. -- Stephane
