38.8 Shell Commands in Dired

The Dired command ! (dired-do-shell-command) reads a shell command string in the minibuffer and runs that shell command on all the specified files. X is a synonym for !. You can specify the files to operate on in the usual ways for Dired commands (see Operating on Files). There are two ways of applying a shell command to multiple files:

• If you use ‘*’ surrounded by whitespace in the shell command, then the command runs just once, with the list of file names substituted for the ‘*’. The order of file names is the order of appearance in the Dired buffer.

  Thus, ! tar cf foo.tar * <RET> runs tar on the entire list of file names, putting them into one tar file foo.tar.

  If you want to use ‘*’ as a shell wildcard with whitespace around it, write ‘*""’. In the shell, this is equivalent to ‘*’; but since the ‘*’ is not surrounded by whitespace, Dired does not treat it specially.

• If the command string doesn't contain ‘*’ surrounded by whitespace, then it runs once for each file. Normally the file name is added at the end.

  For example, ! uudecode <RET> runs uudecode on each file.

• However, if the command string contains ‘?’ surrounded by whitespace, the current file name is substituted for ‘?’ (rather than added at the end). You can use ‘?’ this way more than once in the command, and the same file name replaces each occurrence.

To iterate over the file names in a more complicated fashion, use an explicit shell loop. For example, here is how to uuencode each file, making the output file name by appending ‘.uu’ to the input file name:

     for file in * ; do uuencode "$file" "$file" >"$file".uu; done

The working directory for the shell command is the top-level directory of the Dired buffer.

The ! command does not attempt to update the Dired buffer to show new or modified files, because it doesn't really understand shell commands, and does not know what files the shell command changed. Use the g command to update the Dired buffer (see Dired Updating).