Diff for "BashFAQ/041"

Differences between revisions 1 and 10 (spanning 9 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 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 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 ...

CategoryShell

-  ⇤ ← Revision 1 as of 2007-05-02 23:31:14 → 
  Size: 730
  Editor: redondos
  Comment:
+   ← Revision 10 as of 2013-07-24 15:34:17 → ⇥
  Size: 1013
  Editor: 188-223-3-27
  Comment:
-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 14:
+Line 18:
-If you are programming in the BourneShell instead of Bash, there is a more portable (but less pretty) syntax:
+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:
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+Line 23:
-  case "$foo" in
+  # Bourne
  case $foo in
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+Line 29:
-This should allow you to match variables against globbing-style patterns.  if you need a portable way to match variables against regular expressions, use {{{grep}}} or {{{egrep}}}.
+{{{case}}} allows you to match variables against [[glob|globbing]]-style patterns (including extended globs, if your shell offers them).  If you need a portable way to match variables against [[RegularExpression|regular expressions]], use {{{expr}}}.
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+Line 32:
-  if echo "$foo" | egrep some-regex >/dev/null; then ...
+  # Bourne/POSIX
  if expr "x$foo" : 'x.*bar' >/dev/null; then ...
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+Line 35:
+----
CategoryShell