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Monday, February 25, 2013

PS2 and friends



This post won't be about PlayStation 2, but about my (not so) recent problem with the UNIX shell prompt.

I had a problem with prompt on some remote Linux system. Everything looked fine until the command (with arguments) fitted one line. I was using iTerm2 on MacOSX with full screen mode, so line could be long, but anyway it started to be very annoying. When I tried to move cursor back or jump to the beginning of the line it could end up in the middle of existing text.

I spent a lot of time trying to debug problem. First I tried to find something wrong with my iTerm2 settings, but could not find a thing. Next I started to play with tput (see link 1 and 2). For a moment believed that I had broken my PS2 setting (see 3) and finally, after reading link 4, figured out that I hadn't properly escaped non printing character in colour settings. My 'remote' bash prompt looks currently as printer below and you can see a lot of \[ before not printing characters and \] after them.

\[\e[32m\]\h \[\e[0m\]: \[\e[33m\]\w \[\e[0m\]#>

Reading:

  1. http://tldp.yolinux.com/HOWTO/Bash-Prompt-HOWTO.html
  2. http://tldp.org/LDP/abs/html/terminalccmds.html
  3. http://www.thegeekstuff.com/2008/09/bash-shell-take-control-of-ps1-ps2-ps3-ps4-and-prompt_command/
  4. http://www.ibm.com/developerworks/linux/library/l-tip-prompt/
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