my $string1 = "Hi. My name is Vlad. It is snowy outside.";
my #array = split('.' $string1); ##essentially I want this, but I want the period to be kept
I want to split this string at the ., but I want to keep the period. How can this be accomplished?
You can use lookbehind to do this:
split(/(?<=\.)/, $string)
The regex matches an empty string that follows a period.
If you want to remove the whitespace between the sentences at the same time, you can change it to:
split(/(?<=\.)\s*/, $string)
Positive and negative lookbehind is explained here
If you don't mind the periods being split into their own elements in the array, you can use parentheses to tell split to keep them:
my #array = split(/(\.)/, $string);
Related
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;
I'm trying to find the index of white space in a string in Perl.
For example, if I have the string
stuff/more stuffhere
I'd like to select the word "more" with a substring method. I can find the index of "/" but haven't figured out how to find the index of white space. The length of the substring I'm trying to select will vary, so I can't hard code the index. There will only be one white space in the string (other than those after the end of the string).
Also, if anybody has any better ideas of how to do this, I'd appreciate hearing them. I'm fairly new to programming so I'm open to advice. Thanks.
Just use index:
#!/usr/bin/perl
use warnings;
use strict;
use feature qw{ say };
my $string = 'stuff/more stuffhere';
my $index_of_slash = index $string, '/';
my $index_of_space = index $string, ' ';
say "Between $index_of_slash and $index_of_space.";
The output is
Between 5 and 10.
Which is correct:
0 1
01234567890123456789
stuff/more stuffhere
If by "whitespace" you also mean tabs or whatever, you can use a regular expression match and the special variables #- and #+:
#!/usr/bin/perl
use warnings;
use strict;
use feature qw{ say };
my $string = "stuff/more\tstuffhere";
if ($string =~ m{/.*(?=\s)}) {
say "Between $-[0] and $+[0]";
}
The (?=\s) means is followed by a whitespace character, but the character itself is not part of the match, so you don't need to do any maths on the returned values.
As you stated, you want to select the word between the first /
and the first space following it.
If this is the case, you maybe don't need any index (you need just
the word).
A perfect tool to find something in a text is regex.
Look at the following code:
$txt = 'stuff/more stuffxx here';
if ($txt =~ /\/(.+?) /) {
print "Match: $1.\n";
}
The regex used tries to match:
a slash,
a non-empty sequence of any chars (note ? - reluctant
version), enclosed in a capturing group,
a space.
So after the match $1 contains what was captured by the first
capturing group, i.e. "your" word.
But if for any reason you were interested in starting and ending
offsets to this word, you can read them from $-[1]
and $+[1] (starting / ending indices of the first capturing group).
The arrays #- (#LAST_MATCH_START) and #+ (#LAST_MATCH_END) give offsets of the start and end of last successful submatches. See Regex related variables in perlvar.
You can capture your real target, and then read off the offset right after it with $+[0]
#+
This array holds the offsets of the ends of the last successful submatches in the currently active dynamic scope. $+[0] is the offset into the string of the end of the entire match. This is the same value as what the pos function returns when called on the variable that was matched against.
Example
my $str = 'target and target with spaces';
while ($str =~ /(target)\s/g)
{
say "Position after match: $+[0]"
}
prints
Position after match: 7
Position after match: 18
These are positions right after 'target', so of spaces that come after it.
Or you can capture \s instead and use $-[1] + 1 (first position of the match, the space).
You can use
my $str = "stuff/more stuffhere";
if ($str =~ m{/\K\S+}) {
... substr($str, $-[0], $+[0] - $-[0]) ...
}
But why substr? That's very weird there. Maybe if you told us what you actually wanted to do, we could provide a better alternatives. Here are three cases:
Data extraction:
my $str = "stuff/more stuffhere";
if ( my ($word) = $str =~ m{/(\S+)} ) {
say $word; # more
}
Data replacement:
my $str = "stuff/more stuffhere";
$str =~ s{/\K\S+}{REPLACED};
say $str; # stuff/REPLACED stuffhere
Data replacement (dynamic):
my $str = "stuff/more stuffhere";
$str =~ s{/\K(\S+)}{ uc($1) }e;
say $str; # stuff/MORE stuffhere
Seem like my daily road block. Is this possible? String in qw?
#!/usr/bin/perl
use strict;
use warnings;
print "Enter Your Number\n";
my $usercc = <>;
##split number
$usercc =~ s/(\w)(?=\w)/$1 /g;
print $usercc;
## string in qw, hmm..
my #ccnumber = qw($usercc);
I get Argument "$usercc" isn't numeric in multiplication (*) at
Thanks
No.
From: http://perlmeme.org/howtos/perlfunc/qw_function.html
How it works
qw() extracts words out of your string
using embedded whitsepace as the
delimiter and returns the words as a
list. Note that this happens at
compile time, which means that the
call to qw() is replaced with the list
before your code starts executing.
Additionlly, no interpolation is possible in the string you pass to qw().
Instead of that, use
my #ccnumber = split /\s+/, $usercc;
Which does what you probably want, to split $usercc on whitespace.
I have
print $str;
abcd*%1234$sdfsd..#d
The string would always have only one continuous stretch of numbers, like 1234 in this case. Rest all will be either alphabets or other special characters.
How can I extract the number (1234 in this case) and store it back in str?
This page suggests that I should use \d, but how?
If you don't want to modify the original string, you can extract the numbers by capturing them in the regex, using subpatterns. In list context, a regular expression returns the matches defined in the subpatterns.
my $str = 'abc 123 x456xy 789foo';
my ($first_num) = $str =~ /(\d+)/; # 123
my #all_nums = $str =~ /(\d+)/g; # (123, 456, 789)
$str =~ s/\D//g;
This removes all nondigit characters from the string. That's all that you need to do.
EDIT: if Unicode digits in other scripts may be present, a better solution is:
$str =~ s/[^0-9]//g;
If you wanted to do it the destructive way, this is the fastest way to do it.
$str =~ tr/0-9//cd;
translate all characters in the complement of 0-9 to nothing, delete them.
The one caveat to this approach, and Phillip Potter's, is that were there another group of digits further down the string, they would be concatenated with the first group of digits. So it's not clear that you would want to do this.
The surefire way to get one and only one group of digits is
( $str ) = $str =~ /(\d+)/;
The match, in a list context returns a list of captures. The parens around $str are simply to put the expression in a list context and assign the first capture to $str.
Personally, I would do it like this:
$s =~ /([0-9]+)/;
print $1;
$1 will contain the first group matched the given regular expression (the part in round brackets).
I have this Perl code:
foreach (#tmp_cycledef)
{
chomp;
my ($cycle_code, $close_day, $first_date) = split(/\|/, $_,3);
$cycle_code =~ s/^\s*(\S*(?:\s+\S+)*)\s*$/$1/;
$close_day =~ s/^\s*(\S*(?:\s+\S+)*)\s*$/$1/;
$first_date =~ s/^\s*(\S*(?:\s+\S+)*)\s*$/$1/;
#print "$cycle_code, $close_day, $first_date\n";
$cycledef{$cycle_code} = [ $close_day, split(/-/,$first_date) ];
}
The value of tmp_cycledef comes from output of an SQL query:
select cycle_code,cycle_close_day,to_char(cycle_first_date,'YYYY-MM-DD')
from cycle_definition d
order by cycle_code;
What exactly is happening inside the for loop?
Huh, I'm surprised no one fixed it for you :)
It looks like the person who wrote this was trying to trim leading and trailing whitespace from each field. It's a really odd way to do that, and for some reason he was overly concerned with interior whitespace in each field despite his anchors.
I think that should be the same as trimming the whitespace around the delimiter in the split:
foreach (#tmp_cycledef)
{
s/^\s+//; s/$//; #leading and trailing whitespace on the whole string
my ($cycle_code, $close_day, $first_date) = split(/\s*\|\s*/, $_, 3);
$cycledef{$cycle_code} = [ $close_day, split(/-/,$first_date) ];
}
The key to thinking about split is considering which parts of the string you want to throw away, not just what separates the fields that you want.
For regex part, s/^\s*(\S*(?:\s+\S+)*)\s*$/$1/ do stripping of leading and trailing whitespaces
Each row in #tmp_cycledef is composed of a string formatted following "cycle_code | close_day | first_date".
my ($cycle_code, $close_day, $first_date) = split(/\|/, $_,3);
Split the string into three parts. The following regular expressions are used to strip leading and trailing whitespaces.
The last instruction of the loop creates an entry in the dictionary $cycledef indexed by $cycle_code. The entry is formated is formatted using the following scheme:
[ $close_day, YYYY, MM, DD ]
where $first_date = "YYYY-MM-DD".
#tmp_cycledef: The output of the sql query is stored in this array
foreach (#tmp_cycledef) : For every element in this array.
chomp : remove the \n char from the end of every element.
my ($cycle_code, $close_day, $first_date) = split(/\|/, $_,3);
split the elements into 3 parts and assign the variable to each of the splited element. parts of split are "split(/PATTERN/,EXPR,LIMIT)"
$cycle_code =~ s/^\s*(\S*(?:\s+\S+)*)\s*$/$1/;
$close_day =~ s/^\s*(\S*(?:\s+\S+)*)\s*$/$1/;
$first_date =~ s/^\s*(\S*(?:\s+\S+)*)\s*$/$1/;
This regex part is sripping of leading and trailing whitespaces from each variable.
my god, it's been such a long time since I've read perl... but I'll give it a shot.
you grab a record from #tmp_cycledef, and chomp off the newline at the end, and split it up into the three variables: then, like S.Mark said, each substitution regex strips off the leading and trailing whitespace for each of the three variable. Finally, the values get pushed into a hash as a list, with some debugging code commented out right above it.
hth
Your query gives a set of rows that
are stored in the array
#tmp_cycledef.
We iterate over each row in the
result using: foreach
(#tmp_cycledef).
The result rows might have trailing
newline char, we get rid of them
using chomp.
Next we split the row (which is not
in $_) on the pipe and assign the
first 3 pieces to $cycle_code,
$close_day and $first_date
respectively.
The split pieces might have leading
and trailing white spaces, the next 3
lines are to remove the leading and
trailing white space in the 3
variables.
Finally we make an entry into the
hash %cycledef. The key use is
$cycle_code and the value is an
array whose first element is
$close_day and rest of the elements
are pieces got after splitting
$first_date on hyphen.