[angusgr]

One I learned for the first time the other day is 'paste'. Good for people like me who never fully grokked awk, it joins lines from separate files into a single file.

Say you have two files, one with lines of numbers:

  1
  2
  3

... and one with letters:

  A
  B
  C

$ paste numbers letters

  1	A
  2	B
  3	C

Want CSV?

$ paste -d, numbers letters

  1,A
  2,B
  3,C

Or, with '-s' you can join lines from inside the same file. For instance, you can sum numbers:

$ paste -sd+ numbers

  1+2+3

$ paste -sd+ numbers |bc

  6

(Thanks to a Stack Overflow post somewhere for suggesting that one!)

Useful example: the total resident memory size of all chromium processes:

$ ps --no-headers -o rss -C chromium | paste -sd+ | bc

  793180

[yesbabyyes]

`paste` is also very useful together with stdin redirection and subshells. E.g.:

    paste <(ping 8.8.8.8) <(while true; do iwconfig wlan0 | grep "Bit Rate"; sleep 1; done)

[ralph]

They could drift. Better to do a one-ping ping and run iwconfig once in a loop.