<<Anchor(faq41)>>
== How do I determine whether a variable contains a substring? ==
In [[BASH]]:

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

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

{{{
  # Bash
  my_re='ab*c'
  if [[ $foo =~ $my_re ]]   # bash 3, matches abbbbcde, or ac, etc.
}}}

For more hints on string manipulations in Bash, see [[BashFAQ/100|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*) .... ;;
  esac
}}}

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

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

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CategoryShell