Differences between revisions 1 and 10 (spanning 9 versions)
Revision 1 as of 2007-05-03 00:00:48
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Editor: redondos
Comment:
Revision 10 as of 2009-02-14 04:30:51
Size: 1586
Editor: GreyCat
Comment: add extglob solution
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[[Anchor(faq66)]]
== I want to check if [[ $var == foo || $var == bar || $var = more ]] without repeating $var n times. ==
<<Anchor(faq66)>>
== I want to check if [[ $var == foo || $var == bar || $var == more ]] without repeating $var n times. ==
The portable solution uses `case`:
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   case $var in    # Bourne
case "$var" in
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[[glob|Extended globs]] can also do this within a `[[` command:
{{{
   # bash/ksh -- ksh does not need the shopt
   shopt -s extglob
   if [[ $var = @(foo|bar|more) ]]; then
      ...
   fi
}}}

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 [[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:

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

Extended globs can also do this within a [[ command:

   # bash/ksh -- ksh does not need the shopt
   shopt -s extglob
   if [[ $var = @(foo|bar|more) ]]; then
      ...
   fi

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)