Diff for "BashFAQ/041"

Differences between revisions 2 and 8 (spanning 6 versions)

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
  my_re='ab*c'
  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 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 globbing-style patterns (including extended globs, if your shell offers them). If you need a portable way to match variables against regular expressions, use grep or egrep.

  # Bourne
  if echo "$foo" | grep bar >/dev/null 2>&1; then ...

CategoryShell

-  ⇤ ← Revision 2 as of 2007-05-07 18:44:14 → 
  Size: 722
  Editor: GreyCat
  Comment: minor clean-up
+   ← Revision 8 as of 2010-11-29 22:24:01 → ⇥
  Size: 1001
  Editor: GreyCat
  Comment: fixes, link to 100
-Deletions are marked like this.
+Additions are marked like this.
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-[[Anchor(faq41)]]
+<<Anchor(faq41)>>
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+In [[BASH]]:
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+  # Bash
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-The above works in virtually all versions of Bash.  Bash version 3 also allows regular expressions:
+The above works in virtually all versions of Bash.  Bash version 3 (and up) also allows regular expressions:
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+Line 13:
-  if [[ $foo =~ ab*c ]]   # bash 3, matches abbbbcde, or ac, etc.
+  # Bash
  my_re='ab*c'
  if [[ $foo =~ $my_re ]]   # bash 3, matches abbbbcde, or ac, etc.
-Line 13:
+Line 17:
+For more hints on string manipulations in Bash, see [[BashFAQ/100|FAQ #100]].
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+  # Bourne
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+Line 29:
-{{{case}}} allows you to match variables against globbing-style patterns.  If you need a portable way to match variables against regular expressions, use {{{grep}}} or {{{egrep}}}.
+{{{case}}} allows you to match variables against [[glob|globbing]]-style patterns (including extended globs, if your shell offers them).  If you need a portable way to match variables against [[RegularExpression|regular expressions]], use {{{grep}}} or {{{egrep}}}.
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-  if echo "$foo" | grep bar >/dev/null; then ...
+  # Bourne
  if echo "$foo" | grep bar >/dev/null 2>&1; then ...
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+Line 35:
+----
CategoryShell