how to iterate though delimited values in bash

Question

BASH

input: cat test

  1 a;b;c;d
  2 a;b;c;d
  3 a;b;c;d

desired output is:

  1 a
  1 b
  1 c
  1 d
  2 a
  2 b
  2 c
          


        

Answer 1

Straightforward shell:

IFS=" ;"
shopt noglob # or set -f
while read -r line; do 
  set -- $line; a=$1; shift
  for b; do printf '%s %s\n' "$a" "$b"; done
done
# if data never contains backslash can omit -r from read
# if data never contains glob patterns (? * [..] etc) can omit set -f
# if data never contains backslash and first col never begins with hyphen
# can replace printf with echo "$a" "$b" 

Clever shell, if first column never contains percent or backslash:

IFS=" ;"
shopt noglob # or set -f
while read -r line; do 
  set -- $line; a=$1; shift
  printf "$a %s\n" "$@"
done
# read -r and set -f as above

Both of these leave IFS and (maybe) noglob changed; if this is all or the last part of a script, or a function using (), those changes are to a local instance and discarded. Otherwise either explicitly save and restore, or surround with () so they are discarded.

Similarly both clobber the positional arguments, which generally matters only when in a script or function; if those are needed subsequently, save and restore them, or alternatively in bash or ksh only use a separate explicit array variable:

IFS=" ;"
shopt noglob # or set -f
while read -ra ary; do
  a=${ary[0]}; unset ary[0]
  for b in "${ary[@]}"; do printf '%s %s\n' "$a" "$b"; done
  # or 
  printf "$a %s\n" "${ary[@]}"
done