Bash – Copy multiple files using command `xargs`

bashxargs

I'd like to copy the files searched by command find to the currernt directory

    # find linux books
    find ~ -type f -iregex '.*linux.*\.pdf' -print0 | xargs -0 echo
  # the result
    ../Books/LinuxCollection/Linux_TLCL-17.10.pdf ../Richard Blum, Christine Bresnahan - Linux Command Line and Shell Scripting Bible, 3rd Edition - 2015.pdf ..

Test to copy the files to the current dir using command `cp'

 find ~ -type f -iregex '.*linux.*\.pdf' -print0 | xargs -0 cp .

Get error:

    usage: cp [-R [-H | -L | -P]] [-fi | -n] [-apvXc] source_file target_file
           cp [-R [-H | -L | -P]] [-fi | -n] [-apvXc] source_file ... target_directory

I work out the problem with command substitution

    cp $(find ~ -type f -iregex '.*linux.*\.pdf' -print0) .

How to accomplish it with xargs?

Best Answer

As the cp error indicates, the target directory must come last. Since it looks like your cp doesn't have an equivalent of GNU cp's -t option, you have to get xargs to insert the filename between cp and .:

find ... | xargs -0 -I _ cp _ .

where -I is used to tell which string is to be replaced with the input (in this case I'm using _, though {} is also commonly used).

Of course, this can be done with find itself:

find ~ -type f -iregex '.*linux.*\.pdf' -exec cp {} . \;

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Copying multiple files to multiple directories

echo dir[1-3] | xargs -r -n1 cp file[1-5]

Bash – Manipulate file name piped from find command

As other answers have already identified, ${f%.*} is expanded by the shell before it runs the xargs command. You need this expansion to happen once for each file name, with the shell variable f set to the file name (passing -I f doesn't do that: xargs has no notion of shell variable, it looks for the string f in the command, so if you'd used e.g. xargs -I e echo … it would have executed commands like ./somedir/somefile.wmacho .mp3).

Keeping on this approach, tell xargs to invoke a shell that can perform the expansion. Better, tell find — xargs is a largely obsolete tool and is hard to use correctly, as modern versions of find have a construct that does the same job (and more) with fewer plumbing difficulties. Instead of find … -print0 | xargs -0 command …, run find … -exec command … {} +.

find . -name '*.wma' -type f -exec sh -c 'for f; do echo "${f%.*}.mp3"; done' _ {} +

The argument _ is $0 in the shell; the file names are passed as the positional arguments which for f; do … loops over. A simpler version of this command executes a separate shell for each file, which is equivalent but slightly slower:

find . -name '*.wma' -type f -exec sh -c 'echo "${0%.*}.mp3"' {} \;

You don't actually need to use find here, assuming you're running a reasonably recent shell (ksh93, bash ≥4.0, or zsh). In bash, put shopt -s globstar in your .bashrc to activate the **/ glob pattern to recurse in subdirectories (in ksh, that's set -o globstar). Then you can run

for f in **/*.wma; do
  echo "${f%.*}.mp3"
done

(If you have directories called *.wma, add [ -f "$f" ] || continue at the beginning of the loop.)

Best Answer

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Copying multiple files to multiple directories

Bash – Manipulate file name piped from find command

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