I want to find a substring and move it in the string instead of replacing (for example, moving it from the beginning to the end of the string).
'THIS the rest of the string' -> 'the rest of the string THIS'
I do this by the following code
preg_match('/^(THIS).?/', $str, $match);
$str = trim( $str . $match[1] );
$str = preg_replace('/^(THIS).?/', '', $str);
There should be an easier way to do this with one regex.
You may use
$re = '/^(THIS)\b\s*(.*)/s';
$str = 'THIS the rest of the string';
$result = preg_replace($re, '$2 $1', $str);
See the regex demo and a PHP demo.
Details
^ - start of string
(THIS) - Group 1 (referenced to with $1 from the replacement pattern): THIS
\b - a word boundary (if you do not need a whole word, you may remove it)
\s* - 0+ whitespaces (if there is always at least one whitespace, use \s+ and remove \b, as it will become redundant)
(.*) - Group 2 (referenced to with $2 from the replacement pattern): the rest of the string (s modifier allows . match line break chars, too).
Related
I need a regex to match \' <---- literally backslash apostrophe.
my $line = '\'this';
$line =~ s/(\o{134})(\o{047})/\\\\'/g;
$line =~ s/\\'/\\\\'/g;
$line =~ s/[\\][']/\\\\'/g;
printf('%s',$line);
print "\n";
All I get out of this is
'this
When what I want is
\\'this
This occurs whether the string is declared using ' or ". This was a test script for tracking down a file parsing bug. I wanted to confirm that the regex was working as expected.
I don't know if when the backslash apostrophe is parsed by the regex it is not treated as 2 characters, but is instead treated as an escaped apostrophe.
Either way. what is the best way to match \' and print out \\'? I don't want to escape any other back slashes or apostrophes and I can't change the text I am parsing, just the way it is handled and outputted.
s/\\'/\\\\'/g
All three of your patterns match a backslash followed by a quote, the above being the simplest.
Your testing was in vain because your string doesn't contain any backslashes. Both string literals "\'this" (from earlier edit) and '\'this' (from later edit) produce the string 'this.
say "\'this"; # 'this
say '\'this'; # 'this
To produce the string \'this, you could use either of the following string literals (among others):
"\\'this"
'\\\'this'
say "\\'this"; # \'this
say '\\\'this'; # \'this
The answer is, of course
s/[\\][']/\\\\'/g
This will match
\'this
And substitute with this
\\'this
This was the only way I could get it to work.
Perl
Too much "regexing" in your snippet. Try:
my $line = '\'this';
$line =~ s/'/\\\\\'/g;
printf('%s',$line);
print "\n";
# \\'this
or... if you want another mode:
my $line = '\'this';
$line =~ s/'/\\'/g;
printf('%s',$line);
print "\n";
# \'this
I found how to split a string by whitespaces, but that only takes into an account a single character. In my case, I have comments pasted into a file that includes newlines and whitespaces. I have them separated by this string: [|]
So I need to split my $string into an array for example, where $string =
This is a comment.
This is a newline.
This is the end[|]This is second comment.
This is second newline.
[|]Last comment
Gets split into $array[0], $array[1], and $array[2] which include the newlines and whitespaces. Separated by [|]
Every example I find on the web uses a single character, such as space or newline, to split strings. In my case I have to use a more specific identifier, which is why I selected [|] but having troubles splitting it by this.
I have tried to limit it to parse by a single '|' character with this code:
my #words = split /|/, $string;
foreach my $thisline (#words) {
print "This line = '" . $thisline . "'\n";
But this seems to split the entire string, character-by-character into #words.
[, |, and ] are all special characters in regular expressions -- | is used to separate options, and […] are used to specify character sets. Using an unquoted | makes the expression match the empty string (more specifically: the empty string or the empty string), causing it to match and split on every character boundary. These characters must be escaped to use them literally in an expression:
my #words = split /\[\|\]/, $string;
Since all the lines makes this visually confusing, you should probably use m{} quotes instead of //, and \Q…\E to quote a range of characters instead of a separate backslash for each one. (This is functionally identical, it's just a little easier to read.)
my #words = split m{\Q[|]\E}, $string;
E.g:
$myVar="this###!~`%^&*()[]}{;'".,<>?/\";
I am not able to export this variable and use it as it is in my program.
Use q to store the characters and use the quotemeta to escape the all character
my $myVar=q("this###!~`%^&*()[]}{;'".,<>?/\");
$myVar = quotemeta($myVar);
print $myVar;
Or else use regex substitution to escape the all character
my $myVar=q("this###!~`%^&*()[]}{;'".,<>?/\");
$myVar =~s/(\W)/\\$1/g;
print $myVar;
This is what quotemeta is for, if I understand your quest
Returns the value of EXPR with all non-"word" characters backslashed. (That is, all characters not matching /[A-Za-z_0-9]/ will be preceded by a backslash in the returned string, regardless of any locale settings.) This is the internal function implementing the \Q escape in double-quoted strings.
Its use is very simple
my $myVar = q(this###!~`%^&*()[]}{;'".,<>?/\\);
print "$myVar\n";
my $quoted_var = quotemeta $myVar;
print "$quoted_var\n";
Note that we must manually escape the last backslash, to prevent it from escaping the closing delimiter. Or you can tack on an extra space at the end, and then strip it (by chop).
my $myVar = q(this###!~`%^&*()[]}{;'".,<>?/\ );
chop $myVar;
Now transform $myVar like above, using quotemeta.
I take the outside pair of " to merely indicate what you'd like in the variable. But if they are in fact meant to be in the variable then simply put it all inside q(), since then the last character is ". The only problem is a backslash immediately preceding the closing delimiter.
If you need this in a regex context then you use \Q to start and \E to end escaping.
Giving Thanks to:
What's between \Q and \E is treated as normal characters, not regexp characters. For example,
'.' =~ /./; # match
'a' =~ /./; # match
'.' =~ /\Q.\E/; # match
'a' =~ /\Q.\E/; # no match
It doesn't stop variables from being interpolated.
$search = '.';
'.' =~ /$search/; # match
'a' =~ /$search/; # match
'.' =~ /\Q$search\E/; # match
'a' =~ /\Q$search\E/; # no match
Here is the text to trim:
/home/netgear/Desktop/WGET-1.13/wget-1.13/src/cmpt.c:388,error,resourceLeak,Resource leak: fr
From the above text I need to get the data next to ":". How do I get 388,error,resourceLeak,Resource leak: fr?
You can use split to separate a string into a list based on a delimiter. In your case the delimiter should be a ::
my #parts = split ':', $text;
As the text you want to extract can also contain a :, use the limit argument to stop after the first one:
my #parts = split ':', $text, 2;
$parts[1] will then contain the text you wanted to extract. You could also pass the result into a list, discarding the first element:
my (undef, $extract) = split ':', $text, 2;
Aside from #RobEarl's suggestion of using split, you could use a regular expression to do this.
my ($match) = $text =~ /^[^:]+:(.*?)$/;
Regular expression:
^ the beginning of the string
[^:]+ any character except: ':' (1 or more times)
: match ':'
( group and capture to \1:
.*? any character except \n (0 or more times)
) end of \1
$ before an optional \n, and the end of the string
$match will now hold the result of capture group #1..
388,error,resourceLeak,Resource leak: fr
I wrote a perl script whihc will output a list containing similar entries like below:
$var = ' whatever'
$var contains: a single quote, a space, the word whatever, single quote
actually, this is key of a hash and i want to pull the value for the same. but due to the single quotes and a space in betweene, i am not able to pull the hash key value.
So, i want to strip $var as below:
$var = whatever
meaning remove the single quote, the space and the trailing single quote.
so that I can use $var as hash key to pull the respective value.
could you guide me on a perl oneliner for the same.
thnaks.
Here is several ways to do it, but beware - modifying the keys in a hash can end with unwanted results, like:
use strict;
use warnings;
use Data::Dumper;
my $src = {
"a a" => 1,
" a a " => 2,
"' a a '" => 3,
};
print "src: ", Dumper($src);
my $trg;
#$trg{ map { s/^[\s']*(.*?)[\s']*$/$1/; $_ } keys %$src } = values %$src;
print "copy: ", Dumper($trg);
will produce:
src: $VAR1 = {
' a a ' => 2,
'\' a a \'' => 3,
'a a' => 1
};
copy: $VAR1 = {
'a a' => 1
};
Any regex is possible do explain with YAPE::Regex::Explain module. (from CPAN). For the above regex:
use YAPE::Regex::Explain;
print YAPE::Regex::Explain->new( qr(^[\s']*(.*?)[\s']*$) )->explain;
will produce:
The regular expression:
(?-imsx:^[\s']*(.*?)[\s']*$)
matches as follows:
NODE EXPLANATION
----------------------------------------------------------------------
(?-imsx: group, but do not capture (case-sensitive)
(with ^ and $ matching normally) (with . not
matching \n) (matching whitespace and #
normally):
----------------------------------------------------------------------
^ the beginning of the string
----------------------------------------------------------------------
[\s']* any character of: whitespace (\n, \r, \t,
\f, and " "), ''' (0 or more times
(matching the most amount possible))
----------------------------------------------------------------------
( group and capture to \1:
----------------------------------------------------------------------
.*? any character except \n (0 or more times
(matching the least amount possible))
----------------------------------------------------------------------
) end of \1
----------------------------------------------------------------------
[\s']* any character of: whitespace (\n, \r, \t,
\f, and " "), ''' (0 or more times
(matching the most amount possible))
----------------------------------------------------------------------
$ before an optional \n, and the end of the
string
----------------------------------------------------------------------
) end of grouping
----------------------------------------------------------------------
In short the: s/^[\s']*(.*?)[\s']*$/$1/; mean:
at the beginning of the string match whitespaces or apostrophe as much times is possible,
then match anything
match at the end of string whitespaces or apostrophes as much times as possible
and keep the only the "anything" part
#!/usr/bin/perl
$string = "' my string'";
print $string . "\n";
$string =~ s/'//g;
$string =~ s/^ //g;
print $string;
Output
' my string'
my string
$var =~ tr/ '//d;
see: tr operator
or, by regex
$var =~ s/(?:^['\s]+)|'//g;
The latter will keep the spaces in the middle of the word, the former removes all spaces and single quotes.
A short test:
...
$var = q{' what ever'};
$var =~ s/
(?: # find the following group
^ # at string begin, followed by
['\s]+ # space or single quote, one or more
) # close group
| # OR
' # single quotes in the while string
//gx ; # replace by nothing, use formatted regex (x)
print "|$var|\n";
...
prints:
|what ever|
as expected.