Differences between revisions 8 and 15 (spanning 7 versions)
Revision 8 as of 2008-11-22 14:09:49
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Editor: localhost
Comment: converted to 1.6 markup
Revision 15 as of 2015-06-20 07:58:04
Size: 1525
Editor: ormaaj
Comment: Eliminate `while shift'
Deletions are marked like this. Additions are marked like this.
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The portable solution uses `case`:
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Here's a portable solution:
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   # Bourne
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And here's one that uses `=~` (which requires bash 3.0 or higher): In Bash and ksh, [[glob|Extended globs]] can also do this within a `[[` command:
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   regex='^(foo|bar|more)$'
   if [[ $var =~ $regex ]]; then
   # bash/ksh
   if [[ $var == @(foo|bar|more) ]]; then
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This one '''only works in bash 3.1''' and '''some 3.2 revisions''' (it is untested in 3.0): Alternatively, you may loop over a list of patterns, checking each individually.
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   if [[ $var =~ '^(foo|bar|more)$' ]]; then
      ...
   fi
#!/usr/bin/env bash
# bash/ksh93

[[ -v BASH_VERSION ]] && shopt -s extglob

# usage: pmatch string pattern [ pattern ... ]
function any {
    [[ -n $1 ]] || return
    typeset pat match=$1
    shift

    for pat; do
        [[ $match == $pat ]] && return
    done

    return 1
}

var='foo bar'
if any "$var" '@(bar|baz)' foo\* blarg; then
    echo 'var matched at least one of the patterns!'
fi
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The `=~` operator behavior changes drastically between 3.1 and 3.2, so be careful with it. The above expression is tested to work in bash ''3.1'' and ''3.2.{13,15,17}''; and it doesn't work in ''3.2.0''.
Please also note that the regexp does not need to be quoted in the 3.2 revisions where it works. --[[redondos]]
For logical conjunction (return true if `$var` matches all patterns), ksh93 can use the `&` pattern delimiter.
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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 {{{
    # ksh93 only
    [[ $var == @(foo&bar&more) ]] && ...
}}}
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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 For shells that support only the ksh88 subset (extglob patterns), you may [[http://en.wikipedia.org/wiki/DeMorgan%27s_Law | DeMorganify]] the logic using the negation sub-pattern operator.

{{{
    # bash/ksh88/etc...
    [[ $var == !(!(foo)|!(bar)|!(more)) ]] && ...
}}}

But this is quite unclear and not much shorter than just writing out separate expressions for each pattern.
----
CategoryShell

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

In Bash and ksh, Extended globs can also do this within a [[ command:

   # bash/ksh
   if [[ $var == @(foo|bar|more) ]]; then
      ...
   fi

Alternatively, you may loop over a list of patterns, checking each individually.

# bash/ksh93

[[ -v BASH_VERSION ]] && shopt -s extglob

# usage: pmatch string pattern [ pattern ... ]
function any {
    [[ -n $1 ]] || return
    typeset pat match=$1
    shift

    for pat; do
        [[ $match == $pat ]] && return
    done

    return 1
}

var='foo bar'
if any "$var" '@(bar|baz)' foo\* blarg; then
    echo 'var matched at least one of the patterns!'
fi

For logical conjunction (return true if $var matches all patterns), ksh93 can use the & pattern delimiter.

    # ksh93 only
    [[ $var == @(foo&bar&more) ]] && ...

For shells that support only the ksh88 subset (extglob patterns), you may DeMorganify the logic using the negation sub-pattern operator.

    # bash/ksh88/etc...
    [[ $var == !(!(foo)|!(bar)|!(more)) ]] && ...

But this is quite unclear and not much shorter than just writing out separate expressions for each pattern.


CategoryShell

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