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Asked: 2011-03-09 02:50:40 +0800 CST

how to change permissions of specific file type

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 file * |  grep 'ASCII text' | chmod -x 
chmod: missing operand
Try `chmod --help' for more information.

The above command gives me error.Basically I am trying to find all the files whose type is ASCII and change their permissions to -x.What mistake is there in above syntax?

bash chmod shell-scripting

4 Answers

  1. Best Answer

    One: grep 'ASCII text' returns not only the file name, but also the type of the file itself; you need to process the output to return only the file name

    Two: chmod does not accept arguments from STDIN, which is what you're trying to do with the pipe |. You'll have to either use xargs or wrap the above in a for loop

    That said, here are two solutions for you:

    Solution #1: With Pipes

    file * | awk '/ASCII text/ {gsub(/:/,"",$1); print $1}' | xargs chmod -x

    Solution #2: With for-loop

    for fn in $(file * | awk '/ASCII text/ {gsub(/:/,"",$1); print $1}'); do chmod -x "$fn"; done

    Pick yer poison :-)

    • 3

  2. This should work regardless of whether filenames contain spaces or colons:

    find -maxdepth 1 -type f -exec sh -c 'file -b "{}" | grep -sq ASCII' \; -print0 | xargs -0 chmod -x

    You can remove the -maxdepth 1 to make it recursive.

    There may be false positives if filenames themselves contain the string "ASCII".

    Edit:

    I incorporated pepoluan's suggestion of using the -b option for file so the filename isn't output for the test by grep. This should eliminate false positives.

    • 2 
  3. for f in `file * | grep "ASCII text" | awk "{print \\$1}" | awk -F ":" "{print \\$1}"`; do chmod -x "$f"; done
    • 1

  4. And another one liner - be aware of the need to strip the : ASCII Text and quote the names too

    file * | grep 'ASCII text' | sed  's|\(^.*\):.*|\"\1\"|'| xargs chmod -x
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