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Full Discussion: sed doubt in extracting
Top Forums Shell Programming and Scripting sed doubt in extracting Post 302427847 by pludi on Tuesday 8th of June 2010 05:54:48 AM
Old 06-08-2010
Code:
s/[^x]//g

This means "replace the first character which isn't a 'x' with nothing". Since that's done as soon as the first 't' is replaced, sed is finished. If you want to remove all characters leading up to the first 'x', use
Code:
s/[^x]*//g

In the second snipped:
Code:
echo 'x_a_b_a_c_a_d' | sed 's/.*\(a\)/\1/'

you're replacing as many characters as possible from the start until the last possible 'a' with the matched 'a'. The rest of the string isn't affected, so 'x_a_b_a_c_a' is replaced by 'a', which changes 'x_a_b_a_c_a_d' to 'a_d'

Third:
Code:
echo 'foo-bar-1.4.5-19.spkg' | sed 's/-[^-]*$//'

means "starting with a dash, take as many non-dash characters as possible until the end, and replace them with nothing", or "remove everything starting from and including the last possible dash".
 

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SUBSTR_REPLACE(3)							 1							 SUBSTR_REPLACE(3)

substr_replace - Replace text within a portion of a string

SYNOPSIS
mixed substr_replace (mixed $string, mixed $replacement, mixed $start, [mixed $length]) DESCRIPTION
substr_replace(3) replaces a copy of $string delimited by the $start and (optionally) $length parameters with the string given in $replace- ment. PARAMETERS
o $string - The input string. An array of strings can be provided, in which case the replacements will occur on each string in turn. In this case, the $replacement, $start and $length parameters may be provided either as scalar values to be applied to each input string in turn, or as arrays, in which case the corresponding array element will be used for each input string. o $replacement - The replacement string. o $start - If $start is positive, the replacing will begin at the $start'th offset into $string. If $start is negative, the replacing will begin at the $start'th character from the end of $string. o $length - If given and is positive, it represents the length of the portion of $string which is to be replaced. If it is negative, it rep- resents the number of characters from the end of $string at which to stop replacing. If it is not given, then it will default to strlen( $string ); i.e. end the replacing at the end of $string. Of course, if $length is zero then this function will have the effect of inserting $replacement into $string at the given $start offset. RETURN VALUES
The result string is returned. If $string is an array then array is returned. EXAMPLES
Example #1 Simple substr_replace(3) examples <?php $var = 'ABCDEFGH:/MNRPQR/'; echo "Original: $var<hr /> "; /* These two examples replace all of $var with 'bob'. */ echo substr_replace($var, 'bob', 0) . "<br /> "; echo substr_replace($var, 'bob', 0, strlen($var)) . "<br /> "; /* Insert 'bob' right at the beginning of $var. */ echo substr_replace($var, 'bob', 0, 0) . "<br /> "; /* These next two replace 'MNRPQR' in $var with 'bob'. */ echo substr_replace($var, 'bob', 10, -1) . "<br /> "; echo substr_replace($var, 'bob', -7, -1) . "<br /> "; /* Delete 'MNRPQR' from $var. */ echo substr_replace($var, '', 10, -1) . "<br /> "; ?> Example #2 Using substr_replace(3) to replace multiple strings at once <?php $input = array('A: XXX', 'B: XXX', 'C: XXX'); // A simple case: replace XXX in each string with YYY. echo implode('; ', substr_replace($input, 'YYY', 3, 3))." "; // A more complicated case where each replacement is different. $replace = array('AAA', 'BBB', 'CCC'); echo implode('; ', substr_replace($input, $replace, 3, 3))." "; // Replace a different number of characters each time. $length = array(1, 2, 3); echo implode('; ', substr_replace($input, $replace, 3, $length))." "; ?> The above example will output: A: YYY; B: YYY; C: YYY A: AAA; B: BBB; C: CCC A: AAAXX; B: BBBX; C: CCC NOTES
Note This function is binary-safe. SEE ALSO
str_replace(3), substr(3), String access and modification by character. PHP Documentation Group SUBSTR_REPLACE(3)
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