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).
#!C:\Perl\bin\perl.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{ $constant{const_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 \@开发者_如何学JAVAlines if @lines;
return;
}
sub parse_block {
my $block = shift;
my ($start_line, @attribs) = @$block;
my %constant;
# Break down first line:
# First separate assignment from option list.
my ($start_head, $start_tail) = split /=/, $start_line;
# work on option list
my @options = split /\s+/, $start_head;
# Recover constant_name from options:
$constant{const_name} = pop @options;
$constant{options} = \@options;
# Now we parse the value/type specifier
@constant{'type', 'value' } = parse_type_value_specifier( $start_tail );
# Parse attribute lines.
# since we've already got multiple per line, get them all at once.
chomp @attribs;
my $attribs = join ' ', @attribs;
# we have one long line of mixed key = "value" or key = <TYPE VALUE>
@attribs = $attribs =~ /\s*(\w+\s+=\s+\w+\s+|\w+\s+=\s+".*?"|\w+\s+=\s+<.*?>)\s*/g;
for my $attrib ( @attribs ) {
warn "$attrib\n";
my ($name, $value) = split /\s*=\s*/, $attrib;
if( $value =~ /^"/ ) {
$value =~ s/^"|"\s*$//g;
}
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:\learning\perl>hello1.pl
vid = 6
Bad line at D:\learning\perl\hello1.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:\learning\perl\hello1.pl line 102, <DATA> line 13.
name = ""
units = ""
vid = 0
Bad line at D:\learning\perl\hello1.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:\learning\perl>
You could notice that 'vid' => '0 ',
(notice the white space)
The code above from the answer. I am studying it. :-)
Thank you.
$myString =~ s/^\s*(.*?)\s*$/$1/;
This will trim whitespace from both sides.
from just the right:
$myString =~ s/\s*$//;
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)
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.
sub trim
{
my $str = $_[0];
$str=~s/^\s+|\s+$//g;
return $str;
}
print trim(" 4 ");
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.
-- routine
sub unspace { my @stringer = @_ ? @_ : $; $ = join( ' ', split(' ')) for @stringer; return wantarray ? @stringer : "@stringer"; }
-- usage
$MySpacedString = ' String with tabs double-spaces and other whitespace areas. '; $MyCleanString = unspace($MySpacedString);
Remove all spaces in a string:
$string =~ s/ //g;
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
parse_type_value_specifier(...)to $value. It was (incorrectly) stated as $attrib.
Remove spaces from variable $test (eq rtrim(ltrim(@sStr))
from Transact SQL:
$test =~s/^\s*(\S*)\s*$/$1/;
If you are willing to use a CPAN module then String::Util
, or the somewhat more economical Text::Trim
would be possible choices.
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
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