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Top Forums UNIX for Dummies Questions & Answers Testing for non-zero length string Post 302580084 by longjon on Wednesday 7th of December 2011 12:00:53 PM
Old 12-07-2011
Testing for non-zero length string

Hello, can someone please explain to me why this happens:

Code:
myserver#echo "$nothing"

myserver#if [ -z ${nothing} ]; then echo "nothing is a zero length string"; fi
nothing is a zero length string
myserver#if [ -n ${nothing} ]; then echo "nothing is also a non-zero length string, apparently"; fi
nothing is also a non-zero length string, apparently

Surely an undefined variable cannot be both zero-length and non-zero-length at the same time? I always have problems with the -n test flag - does it actually work? Smilie

I am using bash shell on a Solaris 9 server.

TIA,

jon
 

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SUBSTR_COUNT(3) 							 1							   SUBSTR_COUNT(3)

substr_count - Count the number of substring occurrences

SYNOPSIS
int substr_count (string $haystack, string $needle, [int $offset], [int $length]) DESCRIPTION
substr_count(3) returns the number of times the $needle substring occurs in the $haystack string. Please note that $needle is case sensi- tive. Note This function doesn't count overlapped substrings. See the example below! PARAMETERS
o $haystack - The string to search in o $needle - The substring to search for o $offset - The offset where to start counting o $length - The maximum length after the specified offset to search for the substring. It outputs a warning if the offset plus the length is greater than the $haystack length. RETURN VALUES
This function returns an integer. CHANGELOG
+--------+-----------------------------------------------+ |Version | | | | | | | Description | | | | +--------+-----------------------------------------------+ | 5.1.0 | | | | | | | Added the $offset and the $length parameters | | | | +--------+-----------------------------------------------+ EXAMPLES
Example #1 A substr_count(3) example <?php $text = 'This is a test'; echo strlen($text); // 14 echo substr_count($text, 'is'); // 2 // the string is reduced to 's is a test', so it prints 1 echo substr_count($text, 'is', 3); // the text is reduced to 's i', so it prints 0 echo substr_count($text, 'is', 3, 3); // generates a warning because 5+10 > 14 echo substr_count($text, 'is', 5, 10); // prints only 1, because it doesn't count overlapped substrings $text2 = 'gcdgcdgcd'; echo substr_count($text2, 'gcdgcd'); ?> SEE ALSO
count_chars(3), strpos(3), substr(3), strstr(3). PHP Documentation Group SUBSTR_COUNT(3)
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