Understanding regex behaviour when using quantifiers
So, in the above code , sed replaces at the start. does that mean sed using the pattern e* settles to zero occurence ? Why sed was not able to replace Teest string.
I am having trouble parsing rpm filenames in a shell script.. I found a snippet of perl code that will perform the task but I really don't have time to rewrite the entire script in perl. I cannot for the life of me convert this code into something sed-friendly:
if ($rpm =~ /(*)-(*)-(*)\.(.*)/)... (1 Reply)
I have these two files in current dir:
oos.txt
oos_(copy).txt
I execute this find command:find . -regex './oos*.txt'And this outputs only the first file (oos.txt)! :confused:
Only if I add another asterisk to the find find . -regex './oos*.*txt' do I also get the second file... (7 Replies)
Hi,
Please help me to understand the bold segments in the below regex.
Both are of same type whose meaning I am looking for.
find . \( -iregex './\{6,10\}./src' \) -type d -maxdepth 2
Output:
./20111210.0/src
In continuation to above:
sed -e 's|./\(*.\{1,3\}\).*|\1|g'
Output: ... (4 Replies)
I have the following line of code that works wonders. I just don't completely understand it as I am just starting to learn regex. Can you help me understand exactly what is happening here?
find . -type f | grep -v '^\.$' | sed 's!\.\/!!' (4 Replies)
Hi Guys,
Could you please kindly explain what exactly the below SED command will do ?
I am quite confused and i assumed that,
sed 's/*$/ /'
1. It will remove tab and extra spaces .. with single space.
The issue is if it is removing tab then it should be Î right ..
please assist.... (3 Replies)
I am not a big expert in regex and have just little understanding of that language.
Could you help me to understand the regular Perl expression:
^(?!if\b|else\b|while\b|)(?:+?\s+){1,6}(+\s*)\(*\) *?(?:^*;?+){0,10}\{
------
This is regex to select functions from a C/C++ source and defined in... (2 Replies)
Hi everyone,
This regex looks simple and yet it doesn't make sense how it's manipulating the output.
ifconfig -a
eth0 Link encap:Ethernet HWaddr 00:0c:49:c2:35:6v
inet addr:192.16.1.1 Bcast:192.168.226.255 Mask:255.255.255.0
inet6 addr:... (2 Replies)
I'm trying to get some exclusions into our sendmail regular expression for the K command. The following configuration & regex works:
LOCAL_CONFIG
#
Kcheckaddress regex -a@MATCH
+<@+?\.++?\.(us|info|to|br|bid|cn|ru)
LOCAL_RULESETS
SLocal_check_mail
# check address against various regex... (0 Replies)
Hi,
I need some guidance with understanding this Perl script below. I am not the author of the script and the author has not leave any documentation. I supposed it is meant to be 'easy' if you're a Perl or regex guru. I am having problem understanding what regex to use :confused: The script does... (3 Replies)
Hello All,
While googling on regex I came across a site named Regulex Regulex:JavaScript Regular Expression Visualizer
I have written a simple regex ^(a|b|c)(*)@(.*) and could see its visualization; one could export it too, following is the screen shot.
... (3 Replies)
Discussion started by: RavinderSingh13
3 Replies
LEARN ABOUT PHP
preg_replace_callback
PREG_REPLACE_CALLBACK(3) 1 PREG_REPLACE_CALLBACK(3)preg_replace_callback - Perform a regular expression search and replace using a callbackSYNOPSIS
mixed preg_replace_callback (mixed $pattern, callable $callback, mixed $subject, [int $limit = -1], [int &$count])
DESCRIPTION
The behavior of this function is almost identical to preg_replace(3), except for the fact that instead of $replacement parameter, one
should specify a $callback.
PARAMETERS
o $pattern
- The pattern to search for. It can be either a string or an array with strings.
o $callback
- A callback that will be called and passed an array of matched elements in the $subject string. The callback should return the
replacement string. This is the callback signature:
string handler (array $matches) You'll often need the $callback function for a preg_replace_callback(3) in just one place. In
this case you can use an anonymous function to declare the callback within the call to preg_replace_callback(3). By doing it this
way you have all information for the call in one place and do not clutter the function namespace with a callback function's name
not used anywhere else.
Example #1
preg_replace_callback(3) and anonymous function
<?php
/* a unix-style command line filter to convert uppercase
* letters at the beginning of paragraphs to lowercase */
$fp = fopen("php://stdin", "r") or die("can't read stdin");
while (!feof($fp)) {
$line = fgets($fp);
$line = preg_replace_callback(
'|<p>s*w|',
function ($matches) {
return strtolower($matches[0]);
},
$line
);
echo $line;
}
fclose($fp);
?>
o $subject
- The string or an array with strings to search and replace.
o $limit
- The maximum possible replacements for each pattern in each $subject string. Defaults to -1 (no limit).
o $count
- If specified, this variable will be filled with the number of replacements done.
RETURN VALUES preg_replace_callback(3) returns an array if the $subject parameter is an array, or a string otherwise. On errors the return value is NULL
If matches are found, the new subject will be returned, otherwise $subject will be returned unchanged.
CHANGELOG
+--------+---------------------------------+
|Version | |
| | |
| | Description |
| | |
+--------+---------------------------------+
| 5.1.0 | |
| | |
| | The $count parameter was added |
| | |
+--------+---------------------------------+
EXAMPLES
Example #2
preg_replace_callback(3) example
<?php
// this text was used in 2002
// we want to get this up to date for 2003
$text = "April fools day is 04/01/2002
";
$text.= "Last christmas was 12/24/2001
";
// the callback function
function next_year($matches)
{
// as usual: $matches[0] is the complete match
// $matches[1] the match for the first subpattern
// enclosed in '(...)' and so on
return $matches[1].($matches[2]+1);
}
echo preg_replace_callback(
"|(d{2}/d{2}/)(d{4})|",
"next_year",
$text);
?>
The above example will output:
April fools day is 04/01/2003
Last christmas was 12/24/2002
Example #3
preg_replace_callback(3) using recursive structure to handle encapsulated BB code
<?php
$input = "plain [indent] deep [indent] deeper [/indent] deep [/indent] plain";
function parseTagsRecursive($input)
{
$regex = '#[indent]((?:[^[]|[(?!/?indent])|(?R))+)[/indent]#';
if (is_array($input)) {
$input = '<div style="margin-left: 10px">'.$input[1].'</div>';
}
return preg_replace_callback($regex, 'parseTagsRecursive', $input);
}
$output = parseTagsRecursive($input);
echo $output;
?>
SEE ALSO
PCRE Patterns, preg_quote(3), preg_replace(3), preg_last_error(3), Anonymous functions, information about the callback type.
PHP Documentation Group PREG_REPLACE_CALLBACK(3)