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configuregnu-parallel

GNU Parallel doesn't display colors when installed from source

Does anyone know how to install GNU Parallel from source so that the output of certain commands are displayed with colors? I found that the version 20170622 doesn't display colors when running, for example, nightmare with DEBUG=nightmare. 

DEBUG=nightmare parallel node my-script.js

and outputs:

enter image description here

However, the version installed via apt install in Ubuntu (20141022+ds1-1) maintains the colors:

enter image description here

Solution

  • Let us assume your program is:

    echo myfoobar | grep --color foo

    This gives colors if grep detects the output is a tty.

    You can ask GNU Parallel to open the tty by using --tty. --tty defaults to -j1 so you need to set that, too:

    parallel -j100% --tty  'echo myfoobar | grep --color' ::: foo

    The problem is, that buffering is also disabled, so it activates --ungroup, and that is why this is not default. As you can see here the outputs of the jobs mix:

    fu() { echo myfoobar | grep --color "$@"; }
env_parallel -j100% --tty  'echo {}; fu {};sleep 0.1; echo {}; fu {}' ::: foo fo f b ba bar