parcat - cat files or fifos in parallel


parcat [--rm] [-#] file(s) [-#] file(s)


GNU parcat reads files or fifos in parallel. It writes full lines so there will be no problem with mixed-half-lines which you risk if you use:

(cat file1 & cat file2 &) | ...

It is faster than doing:

parallel -j0 --lb cat ::: file*

Arguments can be given on the command line or passed in on stdin (standard input).


  • -#

Arguments following this will be sent to the file descriptor #. E.g.

parcat -1 stdout1 stdout2 -2 stderr1 stderr2

will send stdout1 and stdout2 to stdout (standard output = file descriptor 1), and send stderr1 and stderr2 to stderr (standard error = file descriptor 2).

  • --rm

Remove files after opening. As soon as the files are opened, unlink the files.


Simple line buffered output

traceroute will often print half a line. If run in parallel, two instances may half-lines of their output. This can be avoided by saving the output to a fifo and then using parcat to read the two fifos in parallel:

traceroute > &
traceroute > &
parcat --rm *fifo


GNU parcat is part of GNU parallel. Report bugs to <>.


Copyright (C) 2016-2024 Ole Tange, and Free Software Foundation, Inc.


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GNU parcat uses Perl.


cat(1), parallel(1)