What does // do ? string//string ?? Post: 302137660

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Top Forums Shell Programming and Scripting What does // do ? string//string ?? Post 302137660 by blowtorch on Wednesday 26th of September 2007 06:36:42 AM

09-26-2007

Registered User

From the man page of bash:

Quote:

${parameter//pattern/string}
The pattern is expanded to produce a pattern just as in
pathname expansion. Parameter is expanded and the
longest match of pattern against its value is replaced
with string. In the first form, only the first match
is replaced. The second form causes all matches of
pattern to be replaced with string. If pattern begins
with #, it must match at the beginning of the expanded
value of parameter. If pattern begins with %, it must
match at the end of the expanded value of parameter.
If string is null, matches of pattern are deleted and
the / following pattern may be omitted. If parameter
is @ or *, the substitution operation is applied to
each positional parameter in turn, and the expansion is
the resultant list. If parameter is an array variable
subscripted with @ or *, the substitution operation is
applied to each member of the array in turn, and the
expansion is the resultant list.

I didn't get what this means though... trying to figure that out.

-edit

Ah, got it. This checks if the 'pattern' after being expanded in the same way as pathname expansion, is a substring of 'parameter'. If it is, you can replace it with 'string'. In your case, 'string' doesn't exist, so it will be replaced with nothing. If 'pattern' isn't a substring of 'parameter', then no just 'parameter' is the result. So what the if conditional is checking is whether stringtwo is a substring of stringone. If it is, the resultant expansion will not match with stringone.

Last edited by blowtorch; 09-26-2007 at 07:41 AM..

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LEARN ABOUT PHP

mb_ereg_replace

MB_EREG_REPLACE(3)							 1							MB_EREG_REPLACE(3)

mb_ereg_replace - Replace regular expression with multibyte support

SYNOPSIS

       string mb_ereg_replace (string  $pattern, string  $replacement, string  $string, [string  $option = "msr"])

DESCRIPTION

	Scans $string for matches to $pattern, then replaces the matched text with $replacement

PARAMETERS

	      o $pattern
		- The regular expression pattern.  Multibyte characters may be used in $pattern.

	      o $replacement
		- The replacement text.

	      o $string
		- The string being checked.

	      o $option
		-  Matching  condition	can  be  set by $option parameter. If i is specified for this parameter, the case will be ignored. If x is
		specified, white space will be ignored. If m is specified, match will be executed  in  multiline  mode	and  line  break  will	be
		included  in '.'. If p is specified, match will be executed in POSIX mode, line break will be considered as normal character. If e
		is specified, $replacement string will be evaluated as PHP expression.

RETURN VALUES

	The resultant string on success, or FALSE on error.

NOTES

       Note

	      The internal encoding or the character encoding specified by mb_regex_encoding(3) will be used as the character  encoding  for  this
	      function.

       Warning

	      Never  use  the  e  modifier when working on untrusted input. No automatic escaping will happen (as known from preg_replace(3)). Not
	      taking care of this will most likely create remote code execution vulnerabilities in your application.

SEE ALSO

       mb_regex_encoding(3), mb_eregi_replace(3).

PHP Documentation Group 													MB_EREG_REPLACE(3)