DOKK / manpages / debian 12 / parallel / parcat.1.en
PARCAT(1) parallel PARCAT(1)

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).

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

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:

  mkfifo freenetproject.org.fifo tange.dk.fifo
  traceroute freenetproject.org > freenetproject.org.fifo &
  traceroute tange.dk > tange.dk.fifo &
  parcat --rm *fifo

GNU parcat is part of GNU parallel. Report bugs to <bug-parallel@gnu.org>.

Copyright (C) 2016-2022 Ole Tange, http://ole.tange.dk and Free Software Foundation, Inc.

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GNU parcat uses Perl.

cat(1), parallel(1)

2022-12-18 20221122