Show commands without executing them

Question

I often interactively loop over e.g. my files and want to perform a specific operation on all of them, let\'s say I\'d like to rename all files:

for file in          


        

Answer 1

There is no option for "dry run" as explained by devnull but there is a simple workaround:

debug=
#debug=echo

$debug mv "$file" "${file}_new"

If you remove the comment from the second assignment (without changing anything else), you enable "dry run" for the dangerous mv command.

A more elaborate approach would be to check some condition (like a command line option):

debug=
if [[ ...enable dry run?... ]]; then
    debug=echo
fi

Note: The empty assignment is only necessary when you have the option -u ("Treat unset variables as an error when substituting.") enabled.

Important: This won't work well, when your commands use redirections (because the shell will always do them before the command is even started).