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| [[Anchor(faq41)]] | <<Anchor(faq41)>> |
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| Pattern matching in [[BASH]]: | |
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| if [[ $foo = *bar* ]] | # Bash if [[ $foo == *bar* ]] |
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| The above works in virtually all versions of Bash. Bash version 3 also allows regular expressions: | Bash also supports regular expressions: |
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| if [[ $foo =~ ab*c ]] # bash 3, matches abbbbcde, or ac, etc. | # Bash 3.x # matches e.g ac, abc and abbbbc re='ab*c' if [[ $foo =~ $re ]] |
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| If you are programming in the BourneShell instead of Bash, there is a more portable (but less pretty) syntax: | For more hints on string manipulations in Bash, see [[BashFAQ/100|FAQ #100]]. If you are programming in the POSIX sh syntax or for the BourneShell instead of Bash, there is a more portable (but less pretty) syntax: |
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| case "$foo" in | # Bourne case $foo in |
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| {{{case}}} allows you to match variables against [:globbing:]-style patterns. If you need a portable way to match variables against regular expressions, use {{{grep}}} or {{{egrep}}}. | {{{case}}} allows you to match variables against [[glob|globbing]]-style patterns (including extended globs, if your shell offers them). If you need a portable way to match variables against [[RegularExpression|regular expressions]], use {{{expr}}}. |
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| if echo "$foo" | grep bar >/dev/null; then ... | # Bourne/POSIX if expr "x$foo" : 'x.*bar' >/dev/null; then ... |
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---- CategoryShell |
How do I determine whether a variable contains a substring?
Pattern matching in BASH:
# Bash if [[ $foo == *bar* ]]
Bash also supports regular expressions:
# Bash 3.x # matches e.g ac, abc and abbbbc re='ab*c' if [[ $foo =~ $re ]]
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 $foo in
*bar*) .... ;;
esaccase allows you to match variables against globbing-style patterns (including extended globs, if your shell offers them). If you need a portable way to match variables against regular expressions, use expr.
# Bourne/POSIX if expr "x$foo" : 'x.*bar' >/dev/null; then ...