Shell Programming and Scripting

Quote:

Originally Posted by qneill

This comes up enough I thought I'd drop it here (so the next time I need it I can google for it

Using "IFS", "set", and "for without the in keyword".

Note this will stomp on any arguments passed to the script, and messing with IFS has dangerous side effects to the rest of the script (remember to set it back!)

Code:

  SEP=:  # arbitrary
  FIELDS='yack":blah)::3wasempty:blec!:'

  OLDIFS="$IFS"; IFS=$SEP
  set -- $FIELDS
  for STR
  do
    echo STR=$STR
  done
  IFS="$OLDIFS"

Note what happens if:

Code:

FIELDS='yack":blah):*:3wasempty:blec!:'

And there's no need for that loop if all you're doing is printing the fields:

Code:

set -f
printf "%s\n" $FIELDS
set +f

Your code could also cause failure later in the script if IFS was unset; the behaviour when IFS is unset is not the same as when it is empty.

  SEP=:  # arbitrary
  FIELDS='yack":blah)::3wasempty:blec!:'

  REST="$FIELDS"
  for x in 1 2 3 4 5

There's no need to limit the number of fields; see below.

  do
    # chop off trailing fields
    echo ${REST%%$SEP*}
    # chop off leading field
    REST=${REST#*$SEP}
    # detect last field, works with empty fields too (trailing :)
    [ "$REST" = "${REST#*$SEP}" ] && break
  done

Code:

sep=:  # arbitrary
fields='yack":blah)::3wasempty:blec!:'

while [ -n "$fields" ]
do
  # chop off leading field
  rest=${fields#*"$sep"}

  # print the first field
  printf "%s\n" "${fields%"$sep$rest"}"

  fields=$rest
done