Get the complement of the result of an ls command

Question

Let's say I have a directory with multiple files, all of which are either binary files (files with no declared extensions) and source files (.c extension). I do this:

$ ls

and get:

README.md hello-world.c hello-world get-name.c get-name

and I want to list only files with a specific extensions (say both .c and .md), I do:

ls *.c *.md

and that's ok!

But what if now I want to delete all files that do not have a .c or .md extension, how can I do this?

I know how to do it to files whose extensions are known to me, like:

ls *.c *.md | xargs rm

But how do I tell the command line to delete the files that DON'T match my criteria?

Answer 1

Use find:

find -maxdepth 1 ! -name "*.c" -print0 | xargs -0 ...

Note that -maxdepth, -print0, -r and -0 are found in a few find implementations (were introduced by GNU find/xargs) but are not specified by POSIX. Another way is, as Stéphane mentioned in his comment, using the -exec action of find - remember to use the -exec command {} + form, as it dramatically reduces the number of invocations of command (it has to allow syntax where the filenames are placed at the end though, or else you need to wrap the command inside a sh -c call).

Alternatively grep the output of ls

ls | grep -v "\.c$" | xargs ...

You can filter several extensions either with regular expressions:

... | grep -v "\.\(c\|md\)$" | ...

with extended regexps:

... | grep -Ev "\.(c|md)$" | ...

with fixed strings option (won't match just at the end of filename!):

... | grep -vF ".c
.md" | ...

or by chaining more greps:

... | grep -v "\.c$" | grep -v "\.md$" | ...

That said, find is probably the best option, since with the -print0 option it handles all possible characters in filenames that might need escaping otherwise (provided your find and xargs are able to work with NULL-terminated strings - e.g. the GNU tools are).

Answer 2

In ksh, you can use:

rm -- !(*.c|*.md)

Those globbing extensions are also available in bash after shopt -s extglob and in zsh after setopt kshglob.

The following is the zsh native equivalent:

setopt extended_glob
rm -- ^(*.c|*.md)

The ! in an extglob is "not". For your original command, it's preferred to write this:

rm -- *.c *.md

Parsing the output of ls is unreliable, and will break on some filenames. See the bash wiki for parsing ls.