How do I determine whether a variable contains a substring?


  # Bash
  if [[ $foo = *bar* ]]

The above works in virtually all versions of Bash. Bash version 3 (and up) also allows regular expressions:

  # Bash
  if [[ $foo =~ $my_re ]]   # bash 3, matches abbbbcde, or ac, etc.

For more hints on string manipulations in Bash, see FAQ #100.

If you are programming in the POSIX sh syntax or for the BourneShell instead of Bash, there is a more portable (but less pretty) syntax:

  # Bourne
  case $foo in
    *bar*) .... ;;

case allows you to match variables against globbing-style patterns (including extended globs, if your shell offers them). If you need a portable way to match variables against regular expressions, use expr.

  # Bourne/POSIX
  if expr "x$foo" : 'x.*bar' >/dev/null; then ...


BashFAQ/041 (last edited 2013-07-24 15:34:17 by 188-223-3-27)