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Top Forums UNIX for Dummies Questions & Answers Single or double square brackets Post 302708191 by elixir_sinari on Monday 1st of October 2012 07:31:20 AM
Old 10-01-2012
Quote:
Originally Posted by pamu
Use quotes around it, so you can avoid variable expansion in shell.
What is that, pamu?
Variable expansion will be done by the shell in any case (in case of double-quotes). The double-quotes are to retain the embedded spaces and/or to tell the shell that the parameter exists (in case of null strings) in case of [..] construct.
You don't require the quotes in case [[..]] construct (unless you are testing strings as is).
Also, in the [[..]], globbing is not done.

In ksh88,
Code:
$ [ -z $x ] && echo HI
ksh: test: 0403-004 Specify a parameter with this command.

$ [ -z "$x" ] && echo HI
HI

$ [[ -z $x ]] && echo HI
HI

$ ls *test*
testftp
test.pl
testawk
testsed
testfile
test
testxml

$ [ -e *test* ] && echo HI || echo BYE
HI

[[ -e *test* ]] && echo HI || echo BYE
BYE


Last edited by elixir_sinari; 10-01-2012 at 08:38 AM..
This User Gave Thanks to elixir_sinari For This Post:
 

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PREG_MATCH_ALL(3)							 1							 PREG_MATCH_ALL(3)

preg_match_all - Perform a global regular expression match

SYNOPSIS
int preg_match_all PREG_PATTERN_ORDER (string $pattern, string $subject, [array &$matches], [int $flags], [int $offset]) DESCRIPTION
Searches $subject for all matches to the regular expression given in $pattern and puts them in $matches in the order specified by $flags. After the first match is found, the subsequent searches are continued on from end of the last match. PARAMETERS
o $pattern - The pattern to search for, as a string. o $subject - The input string. o $matches - Array of all matches in multi-dimensional array ordered according to $flags. o $flags - Can be a combination of the following flags (note that it doesn't make sense to use PREG_PATTERN_ORDER together with PREG_SET_ORDER): o PREG_PATTERN_ORDER - Orders results so that $matches[0] is an array of full pattern matches, $matches[1] is an array of strings matched by the first parenthesized subpattern, and so on. <?php preg_match_all("|<[^>]+>(.*)</[^>]+>|U", "<b>example: </b><div align=left>this is a test</div>", $out, PREG_PATTERN_ORDER); echo $out[0][0] . ", " . $out[0][1] . " "; echo $out[1][0] . ", " . $out[1][1] . " "; ?> The above example will output: <b>example: </b>, <div align=left>this is a test</div> example: , this is a test So, $out[0] contains array of strings that matched full pattern, and $out[1] contains array of strings enclosed by tags. o PREG_SET_ORDER - Orders results so that $matches[0] is an array of first set of matches, $matches[1] is an array of second set of matches, and so on. <?php preg_match_all("|<[^>]+>(.*)</[^>]+>|U", "<b>example: </b><div align="left">this is a test</div>", $out, PREG_SET_ORDER); echo $out[0][0] . ", " . $out[0][1] . " "; echo $out[1][0] . ", " . $out[1][1] . " "; ?> The above example will output: <b>example: </b>, example: <div align="left">this is a test</div>, this is a test o PREG_OFFSET_CAPTURE - If this flag is passed, for every occurring match the appendant string offset will also be returned. Note that this changes the value of $matches into an array where every element is an array consisting of the matched string at offset 0 and its string offset into $subject at offset 1. If no order flag is given, PREG_PATTERN_ORDER is assumed. o $offset - Normally, the search starts from the beginning of the subject string. The optional parameter $offset can be used to specify the alternate place from which to start the search (in bytes). Note Using $offset is not equivalent to passing substr($subject, $offset) to preg_match_all(3) in place of the subject string, because $pattern can contain assertions such as ^, $ or (?<=x). See preg_match(3) for examples. RETURN VALUES
Returns the number of full pattern matches (which might be zero), or FALSE if an error occurred. CHANGELOG
+--------+---------------------------------------------------+ |Version | | | | | | | Description | | | | +--------+---------------------------------------------------+ | 5.4.0 | | | | | | | The $matches parameter became optional. | | | | | 5.3.6 | | | | | | | Returns FALSE if $offset is higher than $subject | | | length. | | | | | 5.2.2 | | | | | | | Named subpatterns now accept the syntax | | | (?<name>) and (?'name') as well as (?P<name>). | | | Previous versions accepted only (?P<name>). | | | | +--------+---------------------------------------------------+ EXAMPLES
Example #1 Getting all phone numbers out of some text. <?php preg_match_all("/(? (d{3})? )? (?(1) [-s] ) d{3}-d{4}/x", "Call 555-1212 or 1-800-555-1212", $phones); ?> Example #2 Find matching HTML tags (greedy) <?php // The \2 is an example of backreferencing. This tells pcre that // it must match the second set of parentheses in the regular expression // itself, which would be the ([w]+) in this case. The extra backslash is // required because the string is in double quotes. $html = "<b>bold text</b><a href=howdy.html>click me</a>"; preg_match_all("/(<([w]+)[^>]*>)(.*?)(</\2>)/", $html, $matches, PREG_SET_ORDER); foreach ($matches as $val) { echo "matched: " . $val[0] . " "; echo "part 1: " . $val[1] . " "; echo "part 2: " . $val[2] . " "; echo "part 3: " . $val[3] . " "; echo "part 4: " . $val[4] . " "; } ?> The above example will output: matched: <b>bold text</b> part 1: <b> part 2: b part 3: bold text part 4: </b> matched: <a href=howdy.html>click me</a> part 1: <a href=howdy.html> part 2: a part 3: click me part 4: </a> Example #3 Using named subpattern <?php $str = <<<FOO a: 1 b: 2 c: 3 FOO; preg_match_all('/(?P<name>w+): (?P<digit>d+)/', $str, $matches); /* This also works in PHP 5.2.2 (PCRE 7.0) and later, however * the above form is recommended for backwards compatibility */ // preg_match_all('/(?<name>w+): (?<digit>d+)/', $str, $matches); print_r($matches); ?> The above example will output: Array ( [0] => Array ( [0] => a: 1 [1] => b: 2 [2] => c: 3 ) [name] => Array ( [0] => a [1] => b [2] => c ) [1] => Array ( [0] => a [1] => b [2] => c ) [digit] => Array ( [0] => 1 [1] => 2 [2] => 3 ) [2] => Array ( [0] => 1 [1] => 2 [2] => 3 ) ) SEE ALSO
PCRE Patterns, preg_quote(3), preg_match(3), preg_replace(3), preg_split(3), preg_last_error(3). PHP Documentation Group PREG_MATCH_ALL(3)
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