Differences between revisions 11 and 15 (spanning 4 versions)
Revision 11 as of 2012-04-29 23:44:04
Size: 487
Editor: ormaaj
Comment: rm old comments, rm regex examples because they're stupid and pointless, add category
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.
Line 7: Line 7:
   case "$var" in    case $var in
Line 14: Line 14:
   # bash/ksh -- ksh does not need the shopt
   shopt -s extglob

   if [[ $var = @(foo|bar|more) ]]; then
   # bash/ksh
   if [[ $var == @(foo|bar|more) ]]; then
Line 21: Line 20:
Alternatively, you may loop over a list of patterns, checking each individually.
{{{
#!/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

}}}

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 [[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.

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)