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aneeshep
Asked: 2016-07-21 02:14:12 +0800 CST

What does [co] mean in the "rm -rf filename[co]" command?

  • 772

Let's say I have two files in /tmp:

root@ubuntu:~# touch /tmp/hello.{pyc,py}

root@ubuntu:~# ls /tmp/
hello.py  hello.pyc

Now, lets run rm -rf command with [co] option

root@ubuntu:~# rm -rf /tmp/hello.py[co]

root@ubuntu:~# ls /tmp/
hello.py

Can someone please explain what's happening here? What is the [co] parameter? How can we make it work for other extensions? Say I have foo.js and foo.coffee files, can we do something like rm -rf /tmp/foo.coffe[co] to delete the /tmp/foo.js?

command-line

3 Answers

  1. Best Answer

    [co] isn't a parameter to the rm command - it's a shell glob that matches a pattern equal to a single character from the set [co] - in other words, it matches either a c or an o a the end of the filename. From man bash:

    [...]  Matches any one of the enclosed characters

    To match both foo.coffee and foo.js, since the suffixes don't contain any common substrings at all, the best you could do is foo.* which would match any filename starting with foo. Instead you could use brace expansion e.g.

    rm foo.{coffee,js}
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  2. It is not a parameter but a collection of letters (or a "shell glob"). This is the same:

    rm -rf /tmp/hello.py[co]

    is the same as 

    rm -rf /tmp/hello.pyc
rm -rf /tmp/hello.pyo

    Similar ...

    rm -rf /tmp/hello.py[c-o]

    would delete anything from /tmp/hello.pyc up to and including /tmp/hello.pyo following ASCII ordering. 

    rm -rf /tmp/hello.py[ab][cd]

    would remove ...

    rm -rf /tmp/hello.pyac
rm -rf /tmp/hello.pyad
rm -rf /tmp/hello.pybc
rm -rf /tmp/hello.pybd

    say, i have foo.js and foo.coffee files, can we do something like rm -rf /tmp/foo.coffe[co] to delete the /tmp/foo.js.

    You can make rather fancy methods but for those 2 files I'd just remove them with 1 command for each. Another example getting as close as possible to those 2 files...

    rm /tmp/foo.[cj]*

    would remove files like this ...

    rm /tmp/foo.c*
rm /tmp/foo.j*

    so it would include far more than just these 2 files.

    • 16

  3. It's a shell glob, similar to wildcards * and ? ...in bash, the filename pattern *.[co] matches all filenames that finish with .c or .o.

    The difference with *.[co] versus *.c *.o or *.{c,o} is that the two latter patterns will expand to a dummy *.o if no .o files exist in the directory, while the *.[co] version won't.

    Shell globs are useful for doing file operations in a non-case-sensitive way. For example, if you have a bunch of files with filenames that end with jpg, JPG, Jpg, JPg, etc... and you want to remove all of them, you can do:

    rm *.[Jj][Pp][Gg]
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