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$ ffmpeg -v debug ...

Coloured output.

$ ffmpeg -v debug ... |& less -R

Dull output.

How do I make the output coloured while piping it to something?

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  • 7
    The problem is not with less, but with ffmpeg, which seems to disable coloring when stdout is not associated with a terminal. Some utilities like grep have a --color=always option. You should look at what ffmpeg provides. Commented Aug 22, 2014 at 18:26

2 Answers 2

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For commands that do not have an option similar to --color=always, you can do, e.g. with your example:

script -c "ffmpeg -v debug ..." /dev/null < /dev/null |& less -R

What script does is that it runs the command in a terminal session.

EDIT: Instead of a command string, if you want to be able to provide an array, then the following zsh wrapper script seems to work:

#!/usr/bin/env zsh script -c "${${@:q}}" /dev/null < /dev/null |& less -R
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  • Very useful, didn't know about script! Commented Aug 22, 2014 at 19:24
  • How do I run script with argument array instead of a string? Commented Aug 22, 2014 at 23:34
  • @Vi. I suspect that an argument array isn't used for some reason (same things for the zsh zsh/zpty module). If this is really important, you can write a wrapper that will accept an array and generate the right script invocation (not easy, but perhaps it has already been done somewhere…). Commented Aug 23, 2014 at 0:04
  • @Vi. Is my zsh wrapper script OK for an array in your case? Commented Aug 23, 2014 at 0:19
  • @vinc17, I already have such script: stackoverflow.com/questions/3069163/… . It does not try to quote anything (which I consider insecure), but uses base64 and explicit deserializer. Commented Aug 23, 2014 at 10:28
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As alternative to script, which expectes command line as a string instead of normal array, there is a special mode of reptyr:

reptyr -L ffmpeg -v debug ... < /dev/null |& less -R

Note that not all versions of reptyr have working -L option and accept < /dev/null gracefully. See my pull request for this.

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  • Under Debian/unstable, reptyr -L ... doesn't work ("Unable to read terminal attributes: Inappropriate ioctl for device"), and with the -l option, the color is lost just like with a normal pipe. :( Commented Aug 22, 2014 at 23:55
  • @vinc17, Try feeding some other valid terminal instead of /dev/null to make it happy. I've submitted a pull request to reptyr to make it continue if input is not a terminal. Commented Aug 23, 2014 at 10:26
  • Anyone know how to keep frame= 206 fps= 29 q=-0.0 Lsize= 607kB time=00:00:06.80 bitrate= 731.7kbits/s speed=0.97x printed. Those line disappear when piped. Commented Mar 10, 2021 at 4:47

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