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Revision 2 as of 2007-05-24 14:21:15
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Editor: redondos
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Revision 9 as of 2008-11-22 23:08:34
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Editor: GreyCat
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[[Anchor(faq66)]] <<Anchor(faq66)>>
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The portable solution uses `case`:
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Here's a portable solution:
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And here's one that uses '[[': And here's one that uses `=~` (which requires bash 3.0 or higher):
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   if [[ $var =~ foo|bar|more ]]; then    regex='^(foo|bar|more)$'
if [[ $var =~ $regex ]]; then
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This one '''only works in bash 3.1''' and '''some 3.2 revisions''' (it is untested in 3.0):
{{{
   if [[ $var =~ '^(foo|bar|more)$' ]]; then
      ...
   fi
}}}

The `=~` operator behavior changes drastically between 3.1 and 3.2, so be careful with it. The above expression is tested to work in bash ''3.1'' and ''3.2.{13,15,17}''; and it doesn't work in ''3.2.0''.
Please also note that the regexp does not need to be quoted in the 3.2 revisions where it works. --[[redondos]]

Normally I would never advocate [[BashFAQ/050|sticking code into a variable]] and attempting to use it -- lots of people have ''enormous'' trouble because they try to do that. In the case of `=~`, though, it seems to be required. Personally, I'd just stick with the `case`. --GreyCat

The regexp works as long as it is quoted with bash version ''3.00.15(1)-release'' on CentOS4/RHEL4. I didn't bother checking whether bash is a patched version or not in CentOS4/RHEL4. --ellingsw

I want to check if [[ $var == foo || $var == bar || $var == more ]] without repeating $var n times.

The portable solution uses case:

   case $var in
      foo|bar|more) ... ;;
   esac

And here's one that uses =~ (which requires bash 3.0 or higher):

   regex='^(foo|bar|more)$'
   if [[ $var =~ $regex ]]; then
      ...
   fi

This one only works in bash 3.1 and some 3.2 revisions (it is untested in 3.0):

   if [[ $var =~ '^(foo|bar|more)$' ]]; then
      ...
   fi

The =~ operator behavior changes drastically between 3.1 and 3.2, so be careful with it. The above expression is tested to work in bash 3.1 and 3.2.{13,15,17}; and it doesn't work in 3.2.0. Please also note that the regexp does not need to be quoted in the 3.2 revisions where it works. --redondos

Normally I would never advocate sticking code into a variable and attempting to use it -- lots of people have enormous trouble because they try to do that. In the case of =~, though, it seems to be required. Personally, I'd just stick with the case. --GreyCat

The regexp works as long as it is quoted with bash version 3.00.15(1)-release on CentOS4/RHEL4. I didn't bother checking whether bash is a patched version or not in CentOS4/RHEL4. --ellingsw

BashFAQ/066 (last edited 2015-06-20 07:58:04 by ormaaj)