4 ms·

This is really clever... I usually ended up with adding | grep -v grep like in ps auxww | grep banana | grep -v grep

• dylan604 5y ago
  this does tend to play havoc with $? values if you're used to using those to test grep's results.
  • thewakalix 5y ago
    You can always just reverse the greps.
    • dylan604 5y ago
      the simple things in life elude me. holy cow. i learned the "tag a grep -v grep" at the end and never looked into refining it. but just flipping the greps? nope, not once did that ever occur to me. thanks
  • hddqsb 5y ago
    That's a valid concern, but in this case it won't cause problems -- grep exits with 0 if a line was selected; in the case of `grep -v grep` that means there was a line without "grep", which is what we want. (Also @thewakalix made a good suggestion to reverse the greps.)
    • dylan604 5y ago
      except, your grep -v portion will always return a result so $? will also always return 0. even if your grep banana did not find anything. the reversing the greps will be my new default behavior
      • hddqsb 5y ago
        Nope, try it out: $ printf 'banana\ngrep banana\n' | grep banana | grep -v grep banana $ echo $? 0 $ printf 'grep banana\n' | grep banana | grep -v grep $ echo $? 1 To clarify my previous comment, `grep -v grep` exits with 0 if there was a line without "grep" in the output of `grep banana`.
  • bbarnett 5y ago
    In bash, you can get the rc of piped things, the var eludes me while walking..
    • dylan604 5y ago
      ${PIPESTATUS[@]} for a space delimited list of all exit codes, or replace @ with the position in the pipe chain of the specific command you want. ps auxwww | grep banana | grep -v grep && echo ${PIPESTATUS[1]} type of thing
    • joombaga 5y ago
      You can also set -o pipefail. The first non-zero exit code is returned if there is one.