How do I remove white space in a Perl string?

If I declared a variable $myString with the value '3 ' (notice the white space).
Is there any function to remove the white space for the return value.
A little like SomeFun($myString) then return '3' (without white space).

$myString

'3 '

SomeFun($myString)

'3'

#!C:Perlbinperl.exe
use strict;
use warnings;
use Data::Dumper;

my $fh = *DATA;

print Dumper parse_constant_spec( $fh );


# Parse a constant spec file.
# Pass in a handle to process.
# As long as it acts like a file handle, it will work.
sub parse_constant_spec
my $fh = shift;

my %spec;

# Until file is done:
# Read in a whole block
while( my $block = read_block($fh) )

# Parse the and return key/value pairs for a hash.
my %constant = parse_block( $block );

# Store a ref to the hash in a big hash of all blocks, keyed by constant_name.
$spec $constantconst_name = %constant;



# Return ref to big hash with all block data
return %spec;


# Read a constant definition block from a file handle.
# void return when there is no data left in the file.
# Otherwise return an array ref containing lines to in the block.
sub read_block
my $fh = shift;

my @lines;
my $block_started = 0;

while( my $line = <$fh> )

$block_started++ if $line =~ /^constant/;

if( $block_started )

last if $line =~ /^s*$/;

push @lines, $line;



return @lines if @lines;

return;



sub parse_block w+s+=s+<.*?>)s*/g;

for my $attrib ( @attribs )
warn "$attribn";
my ($name, $value) = split /s*=s*/, $attrib;

if( $value =~ /^"/ )
$value =~ s/^"
elsif( $value =~ /^</ )
$value = [ parse_type_value_specifier( $start_tail ) ];

else
warn "Bad line";


$constant $name = $value;


return %constant;


sub parse_type_value_specifier
my $tvs = shift;

my ($type, $value) = $tvs =~ /<(w+)s+(.*?)>/;

return $type, $value;


__DATA__
constant fixup GemEstabCommDelay = <U2 20>
vid = 6
name = "ESTABLISHCOMMUNICATIONSTIMEOUT"
units = "s"
min = <U2 0>
max = <U2 1800>
default = <U2 20>


constant fixup private GemConstantFileName = <A "C:\TMP\CONST.LOG">
vid = 4
name = "" units = ""


constant fixup private GemAlarmFileName = <A "C:\TMP\ALARM.LOG">
vid = 0
name = ""
units = ""


Output:

D:learningperl>hello1.pl
vid = 6
Bad line at D:learningperlhello1.pl line 102, <DATA> line 8.
name = "ESTABLISHCOMMUNICATIONSTIMEOUT"
units = "s"
min = <U2 0>
max = <U2 1800>
default = <U2 20>
vid = 4
Bad line at D:learningperlhello1.pl line 102, <DATA> line 13.
name = ""
units = ""
vid = 0
Bad line at D:learningperlhello1.pl line 102, <DATA> line 18.
name = ""
units = ""
$VAR1 =
'GemAlarmFileName' =>
'vid' => '0 ',
'options' => [
'constant',
'fixup',
'private'
],
'value' => '"C:\\TMP\\ALARM.LOG"',
'name' => '',
'type' => 'A',
'const_name' => 'GemAlarmFileName',
'units' => ''
,
'GemEstabCommDelay' =>
'vid' => '6 ',
'options' => [
'constant',
'fixup'
],
'value' => '20',
'min' => [
'U2',
'20'
],
'name' => 'ESTABLISHCOMMUNICATIONSTIMEOUT',
'max' => [
'U2',
'20'
],
'default' => [
'U2',
'20'
],
'type' => 'U2',
'units' => 's',
'const_name' => 'GemEstabCommDelay'
,
'GemConstantFileName' =>
'vid' => '4 ',
'options' => [
'constant',
'fixup',
'private'
],
'value' => '"C:\\TMP\\CONST.LOG"',
'name' => '',
'type' => 'A',
'const_name' => 'GemConstantFileName',
'units' => ''

;

D:learningperl>


You could notice that 'vid' => '0 ', (notice the white space)

'vid' => '0 ',

The code above from the answer. I am studying it. :-)

Thank you.

12 Answers
12

$myString =~ s/^s*(.*?)s*$/$1/;


This will trim whitespace from both sides.

from just the right:

$myString =~ s/s*$//;


$value =~ s/s*$//;

print DEST_XML_FILE ""$value"";

$var=~s/t//gs;

If your white space is just spaces, then the following code will remove all spaces:

$mystring =~ tr/ //ds;


/ /

//

sub trim($)

my $string = shift;
$string =~ s/^s+//;
$string =~ s/s+$//;
return $string;



print trim($myString)


print DEST_XML_FILE trim(""$value"");

print DEST_XML_FILE trim("$value");

my $tempString = trim($value);

print DEST_XML_FILE ""$tempString"";

Try this:

# Delete leading/trailing whitespace.
$string =~ s/^s+|s+$//g;


Another potential alternative solution is Text::Trim from CPAN, which will "remove leading and/or trailing whitespace from strings". It has a trim function which may suit your needs.

trim

sub trim

my $str = $_[0];
$str=~s/^s+

print trim(" 4 ");


print DEST_XML_FILE trim(""$value"");

print DEST_XML_FILE trim("$value");

my $tempString = trim($value);

print DEST_XML_FILE ""$tempString"";

Here's a subroutine that will allow you to remove leading and trailing whitespace from a string while also removing excesss whitespaces from within the string and replacing it with a single spaces.

sub unspace
my @stringer = @_ ? @_ : $;
$ = join( ' ', split(' ')) for @stringer;
return wantarray ? @stringer : "@stringer";

$MySpacedString = ' String with tabs double-spaces and other whitespace areas. ';
$MyCleanString = unspace($MySpacedString);

Just looking over your program, I found 3 spots that could be improved or fixed.

I apologize if my code doesn't format well. :-(

In your function parse_block(...), there are 3 items that need attention.

@attribs = $attribs =~ /s*(w+s+=s+w+s+|w+s+=s+".*?"|w+s+=s+<.*?>)s*/g;


To eliminate the white space after vid => '6 ', just don't include the s+ at the end of your first sub-regex.

Write it as:

@attribs = $attribs =~ /s*(w+s+=s+w+|w+s+=s+".*?"|w+s+=s+<.*?>)s*/g;

$value = [ parse_type_value_specifier( $start_tail ) ];


You want this instead:

$value = [ parse_type_value_specifier( $value ) ];


(Note that the parameter to the function should be $value and not $start_tail.) You probably didn't notice this.

In the loop for @attributes, the 'else' in the if/else condition excutes when the 'value' has a plain value, (no "" or <...> items in 'value').

Update: Changed parameter in

Remove spaces from variable $test (eq rtrim(ltrim(@sStr)) from Transact SQL:

$test (eq rtrim(ltrim(@sStr))

$test =~s/^s*(S*)s*$/$1/;


If you are willing to use a CPAN module then String::Util, or the somewhat more economical Text::Trim would be possible choices.

String::Util

Text::Trim

Trimming strings is one of those bike sheds that everyone likes to build! See the short perlmaven tutorial by @szabgab for a small sample of TIMTOWDI fun.

I suggest that you make use of the Text::Trim module, which provides ltrim, rtrim, and trim, all of which will trim the parameters passed, or $_ if you give no parameters. It's not a core module so it may need installing

Text::Trim

ltrim

rtrim

trim

$_

Remove all spaces in a string:

$string =~ s/ //g;


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