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mk1024
Asked: 2018-12-18 14:31:11 +0800 CST

touch in for loop

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ls gives me:

10 11 12 12L 13 16 702 702L

etc., and I'd like to create files

10_ 11_ 12_ 12L_ 13_

and so on. But,

$ for f in *; do touch "$f_"; done

gives me:

touch: cannot touch '': No such file or directory
touch: cannot touch '': No such file or directory
touch: cannot touch '': No such file or directory
touch: cannot touch '': No such file or directory

Also, 

$ for f in *; do touch $f_; done

gives:

Try 'touch --help' for more information.
touch: missing file operand
Try 'touch --help' for more information.
touch: missing file operand
Try 'touch --help' for more information.
touch: missing file operand

I have over 100 files in this directory and haven't intention to do this without script.

bash

1 Answers

  1. You could do it this way:

    for f in *; do touch "${f}_"; done

    man bash/EXPANSION says:

    The braces are required when parameter is a positional parameter with more than one digit, or when parameter is followed by a character which is not to be interpreted as part of its name.

    However, this calls touch for every single file, which is quite inefficient. A better way is to let printf make a list of the files, zero-delimited in case of weird file names, and call touch only as often as needed with the help of xargs:

    printf '%s_\0' * | xargs -0 touch
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