Function to extract columns from an input stream

col() { awk '{print $'$(echo $* | sed -e 's/ /,$/g')'}'; }

April 5, 2012bashoneliners

Explanation

Something I do a lot is extract columns from some input where cut is not suitable because the columns are separated by not a single character but multiple spaces or tabs. So I often do things like:

... | awk '{print $7, $8}'

... which is a lot of typing, additionally slowed down when typing symbols like '{}$ ... Using the simple one-line function above makes it easier and faster:

... | col 7 8

How it works:

  • The one-liner defines a new function with name col
  • The function will execute awk, and it expects standard input (coming from a pipe or input redirection)
  • The function arguments are processed with sed to use them with awk: replace all spaces with ,$ so that for example 1 2 3 becomes 1,$2,$3, which is inserted into the awk command to become the well formatted shell command: awk '{print $1,$2,$3}'

Alternative one-liners

Function to extract columns from an input stream

col() { awk '{print $('$(echo $* | sed -e s/-/NF-/g -e 's/ /),$(/g')')}'; }

December 7, 2012bashoneliners