help in while loop
Hi All,
Can somebody please let me know the meaning of this line.
while ($in)
{
if(/,/) {print before match: $`\t and after match: $'\n\n;}; $x=$';
$y=$`; mysubroutine($x,$y);
}
I know it is a while loop for the file handle ($in) and it will be
executed till the end of file but not getting the meaning of if loop.
What this if loop actually does. Please help
Regards,
Irfan
Re: List of hashes
On 16 Mar, 18:30, [EMAIL PROTECTED] (Yitzle) wrote: On Sun, Mar 16, 2008 at 12:54 PM, John W. Krahn [EMAIL PROTECTED] wrote: push @records, %record I think you want an array of references, not of hashed themselves. Actually, the hash is converted to a list and that list is pushed onto the array. John Darn! I tested it using $array[0] = %hash; in which case it converts to a scalar, not in the list context of push... Sorry! Are subs always return references or only for anonymous lists/hashes? -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] http://learn.perl.org/
Variables initialization
How is it possible to initialize variable using 0 or '' and not having undef warning later on using them? -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] http://learn.perl.org/
Re: Variables initialization
On Mar 17, 2008, at 11:51 , [EMAIL PROTECTED] wrote: How is it possible to initialize variable using 0 or '' and not having undef warning later on using them? Not reassigning to undef. -- fxn -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] http://learn.perl.org/
RE: help in while loop
[EMAIL PROTECTED] asked
Can somebody please let me know the meaning of this line.
while ($in)
{
if(/,/) {print before match: $`\t and after match:
$'\n\n;}; $x=$'; $y=$`; mysubroutine($x,$y);
}
The loop iterates over a filehandle, setting $_ to each
line in turn. If that line contains a comma, then the
line is split at the comma and mysubroutine() is being
called with the parts before and after the comma as
arguments.
My first try at tidying this up would be:
while( my $line = $in )
{
if( my( $pre, $post ) = ( $line =~ m/^(.*?),(.*)/ ) ){
print before match: $pre\t and after match: $post\n\n;
mysubroutine($pre,$post)
}
}
I'm assuming that mysubroutine is only being called if there
actually was a match. Your code above would erroneously call
it for each line.
Using the pre/postmatch captures $' and $` is expensive if
you don't need it all the time (cf. perldoc perlre):
WARNING: Once Perl sees that you need one of $, $`, or $' anywhere in
the program, it has to provide them for every pattern match. This may
substantially slow your program.
Using mysubroutine with arguments would only make sense if
mysubroutine was defined with prototypes and you were trying
to disable that. I'm assuming that in this case it's rather
cargo cult programming.
HTH,
Thomas
--
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
http://learn.perl.org/
Re: Variables initialization
On Mon, Mar 17, 2008 at 6:51 AM, [EMAIL PROTECTED] wrote: How is it possible to initialize variable using 0 or '' and not having undef warning later on using them? snip Well, you can say my $var = 0; but that doesn't prevent the variable from being set to undef later, so if it is possible for the variable to be undef you should guard against it with the defined function (or, if you have Perl 5.10, the // operator): print \$var is , (defined $var ? $var : undef), \n; #Perl 5.8 and below say \$var is , $var // undef; #Perl 5.10 -- Chas. Owens wonkden.net The most important skill a programmer can have is the ability to read. -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] http://learn.perl.org/
xml::twig help
I am extracting addresses from an XML file to process through other
programs using pipe delimiter the following code works but this is going
to get 130,000 records through it it must be very efficient and I cannot
follow the documentation on the best way to do this.
After this simple one is programmed I have to change a much more complex
version of this program.
#!/usr/bin/perl -w
# vi:set sw=4 ts=4 et cin:
# $Id:$
=head1 SYNOPSIS
Extract addresses from an XML file into pipe delimited file.
usage: address_extract.pl xml_file
=cut
use warnings;
use strict;
use XML::Twig qw(:strict);
sub no_pipe
{
my $value = shift;
$value =~ s/\|//g;
return $value;
}
if( ! -f $ARGV[0] ) {
print $ARGV[0] is not a filename, requires filename as first
parameter!\n;
}
my $sort;
my $sort_file = $ARGV[0].'.unsorted';
unlink $sort_file; # in case of rerun
open( $sort, '', $sort_file )
or die Unable to open $sort_file for output $!;
my $ref = XML::Twig-new( twig_handlers={mem=\member} )
or die Unable to open $ARGV[0] $!;
my $member = 0;
$ref-parsefile( $ARGV[0] );
sub get_value
{
my ($mem_ref, $key) = @_;
my @array = $mem_ref-descendants( $key );
return $array[0]-text();
}
sub member {
my ($t, $mem_ref) = @_;
$member++;
my $mem_no = get_value( $mem_ref, 'member' );
my $add1 = get_value( $mem_ref, 'add1' );
my $add2 = get_value( $mem_ref, 'add2' );
my $add3 = get_value( $mem_ref, 'add3' );
my $suburb = get_value( $mem_ref, 'suburb' );
my $state = get_value( $mem_ref, 'state' );
my $pcode = get_value( $mem_ref, 'pcode' );
print $sort join( '|', $member,
$mem_no,
no_pipe( $add1 ),
no_pipe( $add2 ),
no_pipe( $add3 ),
no_pipe( $suburb),
$state,
$pcode,
) .\n;
return 1;
}
Re: help in while loop
On Mar 17, 7:40 am, [EMAIL PROTECTED] (Irfan Sayed) wrote:
Hi All,
Can somebody please let me know the meaning of this line.
while ($in)
{
if(/,/) {print before match: $`\t and after match: $'\n\n;}; $x=$';
$y=$`; mysubroutine($x,$y);
}
I know it is a while loop for the file handle ($in) and it will be
executed till the end of file but not getting the meaning of if loop.
What this if loop actually does. Please help
Try looking at it this way:
while ($in) { ## Go through $in line by line
if (/,/) {## Match a comma
print before match: $`\t and after match: $'\n\n; ## Print
stuff before match and after using $` and $'
}
$x = $'; ## Assign $' to $x
$y = $`; ## Assign $` to $y
mysubroutine($y, $x); ## Run $x and $y through mysubroutine
}
The if block goes through $in, line by line, checking for commas. The
variables $` $ and $' are special: $` = the string before a regular
expression match, $ = the match itself, and $' = the part of the
string after the regular expression match. When it finds a comma, it
prints the strings before and after the match of the comma in the
line. That is, it assigns whatever in the line precedes the comma to
$` and whatever follows to $'. Then it assigns those matches to $x and
$y and runs those as parameters through a subroutine called
mysubroutine. So you can use these special variables in regular
expression matching (as this code does). But many people avoid them
like the plague since they slow down all matching. See perldoc perlvar
for more.
As to what the subroutine mysubroutine actually *does* to or with
those newly assigned variables, there's no way to say without seeing
that code.
Hope this helps, T
--
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
http://learn.perl.org/
Re: List of hashes
On Mon, Mar 17, 2008 at 7:12 AM, [EMAIL PROTECTED] wrote:
Are subs always return references or only for anonymous lists/hashes?
perldoc perlsub
The Perl model for function call and return values is simple: all
functions are passed as parameters one single flat list of scalars,
and all functions likewise return to their caller one single flat list
of scalars. Any arrays or hashes in these call and return lists will
collapse, losing their identities--but you may always use
pass-by-reference instead to avoid this. Both call and return lists
may contain as many or as few scalar elements as you'd like.
perldoc perlref
A reference to an anonymous hash can be created using curly brackets:
$hashref = {
'Adam' = 'Eve',
'Clyde' = 'Bonnie',
};
So. Anonymous hashes create a reference. So its returning a ref. And
subs can't return hashes in any case. Just scalar lists.
--
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
http://learn.perl.org/
Re: help in while loop
On Mar 17, 7:40 am, [EMAIL PROTECTED] (Irfan Sayed) wrote:
Hi All,
Can somebody please let me know the meaning of this line.
while ($in)
{
if(/,/) {print before match: $`\t and after match: $'\n\n;}; $x=$';
$y=$`; mysubroutine($x,$y);
}
I know it is a while loop for the file handle ($in) and it will be
executed till the end of file but not getting the meaning of if loop.
What this if loop actually does. Please help
Does it help to see it this way?
while ($in) {
if (/,/) { # Check each line of $in for a match of ,
(the comma)
print before match: $`\t and after match: $'\n\n; # Print
strings captured before and after the comma
$x = $'; # Assign $x whatever is in $'
$y = $`; # Assign $y whatever is in $`
mysubroutine($x, $y); # Call the subroutine mysubroutine
with $x and $y as parameters
}
}
The variables $` $ and $' are special. They match (repectively) $` -
the stuff before your match, $ - what you match, and $' - the stuff
left after your match. Many people avoid them like the plague since
they slow down regular expression matching. (Check perldoc perlvar.)
As to what mysubroutine actually *does*, there's no way to know
without seeing the code for that subroutine.
Hope this helps, T
--
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
http://learn.perl.org/
diff of two files
Hi All, I want to compare the two files in Perl. The requirement is that file 1 has 20 lines and file2 has 25 lines . I want to see only five lines as output which are there in file2 not in file1 as I know that rest of the 20 lines are same in both the files. I am using the following commands Diff /tmp/dev_path_PRS.DB.01.12.000 /tmp/dep_path_D.PRS.DB.01.12.000.8 As per my understating I should get 5 lines as output Could you please help in getting exact result. Please help Regards, Irfan
Re: functions: rotate and factorial
Rob, Actually you are correct. I was on my way to implement permutation for a given set of numbers. In that context, I had designed my own algo as a part of bigger problem I am trying to solve. That algo requires rotate and factorial. Rotate to get different combinations and factorial to limit for loop. Today, I happened to go through Steinhaus-Johnson-Trotter's algo for the same. It looks elegant and should be efficient. I plan to use this. Question: Does anyone know if perl has inuilt function to implement Steinhaus-Johnson-Trotter's? Regards, Sharan On Fri, Mar 14, 2008 at 8:33 PM, Rob Dixon [EMAIL PROTECTED] wrote: Sharan Basappa wrote: Thanks everybody. I need to use these as a part of algo I am working on. I will get back if I have any comments .. Rotating an array and calculating a factorial are both likely to absorb large amounts of processor time unless your problem is trivial. I'm also intrigued to hear of an algorithm that makes use of factorials. Perhaps your solution needs looking at before you implement it? Rob -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] http://learn.perl.org/
Re: functions: rotate and factorial
On Mon, Mar 17, 2008 at 10:34 AM, Sharan Basappa [EMAIL PROTECTED] wrote: Rob, Actually you are correct. I was on my way to implement permutation for a given set of numbers. In that context, I had designed my own algo as a part of bigger problem I am trying to solve. That algo requires rotate and factorial. Rotate to get different combinations and factorial to limit for loop. Today, I happened to go through Steinhaus-Johnson-Trotter's algo for the same. It looks elegant and should be efficient. I plan to use this. Question: Does anyone know if perl has inuilt function to implement Steinhaus-Johnson-Trotter's?snip snip I don't know what algorithm Algorithm::Permute* uses, but it seems fairly fast. * http://search.cpan.org/dist/Algorithm-Permute/Permute.pm -- Chas. Owens wonkden.net The most important skill a programmer can have is the ability to read. -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] http://learn.perl.org/
RE: Variables initialization
[EMAIL PROTECTED] asked; How is it possible to initialize variable using 0 or '' and not having undef warning later on using them? my $variable = 0; # = initial value goes here HTH, Thomas -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] http://learn.perl.org/
RE: help in while loop
[EMAIL PROTECTED] asked:
I have certain doubts.
What's the meaning of if
mysubroutine was defined with prototypes and you were trying
to disable that sentence.
Could you please elaborate that what's the meaning of this???
When declaring a subroutine, you can optionally also declare
a prototype for it - i.e. the number and type of arguments.
This allows for a limited sort of compile time parameter
checking aswell as parameter type coercion.
For example:
#!/usr/bin/perl -w
use strict;
sub prototyped ($) {
print prototyped args: , join(', ', @_ ), \n;
}
sub unprototyped {
print unprototyped args: , join(', ', @_ ), \n;
}
my @args = qw( foo baz bar );
prototyped @args;
unprototyped @args;
prototyped @args;
__END__
Output:
prototyped args: 3
unprototyped args: foo, baz, bar
prototyped args: foo, baz, bar
The first sub is declared with a prototype to expect a scalar value as the
first argument. This declaration forces the argument @args into scalar context,
so that it evaluates to the number of elements in the array, i.e. 3.
Without the prototype, the array is passed as an array to the subroutine.
If you use the old-style subroutine calling syntax with a prepended , any
prototypes for the function are disabled.
Please see the perlsub manpage (perldoc perlsub) for the
gory details on prototypes and subroutine calling syntax.
HTH,
Thomas
--
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
http://learn.perl.org/
Re: xml::twig help
Ken Foskey wrote:
I am extracting addresses from an XML file to process through other
programs using pipe delimiter the following code works but this is going
to get 130,000 records through it it must be very efficient and I cannot
follow the documentation on the best way to do this.
After this simple one is programmed I have to change a much more complex
version of this program.
#!/usr/bin/perl -w
# vi:set sw=4 ts=4 et cin:
# $Id:$
=head1 SYNOPSIS
Extract addresses from an XML file into pipe delimited file.
usage: address_extract.pl xml_file
=cut
use warnings;
use strict;
use XML::Twig qw(:strict);
sub no_pipe
{
my $value = shift;
$value =~ s/\|//g;
return $value;
}
if( ! -f $ARGV[0] ) {
print $ARGV[0] is not a filename, requires filename as first
parameter!\n;
}
my $sort;
my $sort_file = $ARGV[0].'.unsorted';
unlink $sort_file; # in case of rerun
open( $sort, '', $sort_file )
or die Unable to open $sort_file for output $!;
my $ref = XML::Twig-new( twig_handlers={mem=\member} )
or die Unable to open $ARGV[0] $!;
my $member = 0;
$ref-parsefile( $ARGV[0] );
sub get_value
{
my ($mem_ref, $key) = @_;
my @array = $mem_ref-descendants( $key );
return $array[0]-text();
}
sub member {
my ($t, $mem_ref) = @_;
$member++;
my $mem_no = get_value( $mem_ref, 'member' );
my $add1 = get_value( $mem_ref, 'add1' );
my $add2 = get_value( $mem_ref, 'add2' );
my $add3 = get_value( $mem_ref, 'add3' );
my $suburb = get_value( $mem_ref, 'suburb' );
my $state = get_value( $mem_ref, 'state' );
my $pcode = get_value( $mem_ref, 'pcode' );
print $sort join( '|', $member,
$mem_no,
no_pipe( $add1 ),
no_pipe( $add2 ),
no_pipe( $add3 ),
no_pipe( $suburb),
$state,
$pcode,
) .\n;
return 1;
}
What is your question? I ran you program against XML data like
root
mem
membermember/member
add1add1/add1
add2add2/add2
add3add3/add3
suburbsuburb/suburb
statestate/state
pcodepcode/pcode
/mem
/root
and it seemed to work fine.
I would only change it cosmetically, for instance it would be nicer to
pull the first command-line parameter off into a variable, and you need
to die if there isn't one, not just print a message and carry on.
my $file = shift;
unless ($file and -f $file) {
die $file is not a filename, requires filename as first parameter!\n;
}
also, you could replace all your calls to get_value with
my $mem_no = $mem_ref-first_child('member')-text;
and so on, but there seems to be no problem with the basic
functionality. Let us know if you need any further help.
HTH,
Rob
--
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
http://learn.perl.org/
Re: Hash CSV
On Mar 14, 3:26 pm, [EMAIL PROTECTED] (Manoj) wrote:
When using Data: Dumper is taking more time for my 1 lines of CSV file.
This solved a few queries...and the benchmark was a new value addition for
me. Thanks
2) Is there any optimal method for reading a CSV file and put to
hash table.
May have better approaches however this read CSV into Hash
use Data::Dumper;
open(INFILE, , sample.csv) or die $!;
my %hsh;
%hsh = ( %hsh, (split(/,/, $_))[1,2] ) while ( INFILE );
That is a *very* inefficient way to populate a hash as you are copying
the entire hash for every record in the file. Better to add the keys
and values individually:
my %hsh;
while ( INFILE ) {
chomp;
my ( $key, $value ) = split /,/;
}
print Dumper \%hsh;
John
- Show quoted text -
Suppose my csv file has 5 columns: f id fa mo ge
Will my ($key, $value) = split/,/; still work?
Is there any other mothod that is more efficient?
JB
--
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
http://learn.perl.org/
perl warnings
Hello,
I have a CGI script; when it runs the very first time I define some variables
my $action = $q-param('action');
The first time it runs, parameter 'action' isn't defined so that is
how I check that it is running the first time and do my things
if ($aciton eq ) {...}
elsif ($action eq submit) {...}
the elsif runs if I hit a button on a form which has a hidden field
that sets action=submit. My question is that the script produces a
warning on the if statement Use of uninitialized value in string eq
. How can I get rid of that without using no warnings. I tried 'if
(defined($action))' but that still produces a warning.
Regards,
Kash
--
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
http://learn.perl.org/
Re: diff of two files
[EMAIL PROTECTED] wrote: I want to compare the two files in Perl. The requirement is that file 1 has 20 lines and file2 has 25 lines . I want to see only five lines as output which are there in file2 not in file1 as I know that rest of the 20 lines are same in both the files. I am using the following commands Diff /tmp/dev_path_PRS.DB.01.12.000 /tmp/dep_path_D.PRS.DB.01.12.000.8 C:\hometype test.pl use strict; Diff /tmp/dev_path_PRS.DB.01.12.000 /tmp/dep_path_D.PRS.DB.01.12.000.8 C:\homeperl test.pl Bareword Diff not allowed while strict subs in use at test.pl line 2. Bareword tmp not allowed while strict subs in use at test.pl line 2. Bareword dev_path_PRS not allowed while strict subs in use at test.pl line 2. Bareword DB not allowed while strict subs in use at test.pl line 2. Bareword tmp not allowed while strict subs in use at test.pl line 2. Bareword dep_path_D not allowed while strict subs in use at test.pl line 2. Bareword PRS not allowed while strict subs in use at test.pl line 2. Bareword DB not allowed while strict subs in use at test.pl line 2. Execution of test.pl aborted due to compilation errors. C:\home The FAQ entry perldoc -q difference.+arrays may be useful. -- Gunnar Hjalmarsson Email: http://www.gunnar.cc/cgi-bin/contact.pl -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] http://learn.perl.org/
Re: perl warnings
I think you want:
if( defined $q-param('action') ) {
} else {
}
--
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
http://learn.perl.org/
Re: perl warnings
Kashif Salman wrote:
I have a CGI script; when it runs the very first time I define some variables
my $action = $q-param('action');
The first time it runs, parameter 'action' isn't defined so that is
how I check that it is running the first time and do my things
if ($aciton eq ) {...}
elsif ($action eq submit) {...}
the elsif runs if I hit a button on a form which has a hidden field
that sets action=submit. My question is that the script produces a
warning on the if statement Use of uninitialized value in string eq
. How can I get rid of that without using no warnings. I tried 'if
(defined($action))' but that still produces a warning.
if ( ! $action ) {...}
--
Gunnar Hjalmarsson
Email: http://www.gunnar.cc/cgi-bin/contact.pl
--
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
http://learn.perl.org/
Re: perl warnings
On Mon, Mar 17, 2008 at 11:46 AM, Gunnar Hjalmarsson [EMAIL PROTECTED] wrote:
Kashif Salman wrote:
I have a CGI script; when it runs the very first time I define some
variables
my $action = $q-param('action');
The first time it runs, parameter 'action' isn't defined so that is
how I check that it is running the first time and do my things
if ($aciton eq ) {...}
elsif ($action eq submit) {...}
the elsif runs if I hit a button on a form which has a hidden field
that sets action=submit. My question is that the script produces a
warning on the if statement Use of uninitialized value in string eq
. How can I get rid of that without using no warnings. I tried 'if
(defined($action))' but that still produces a warning.
if ( ! $action ) {...}
--
if( defined $q-param('action') )#still produces the warning
if ( ! $action ) #worked
thanks
--
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
http://learn.perl.org/
Re: perl warnings
Kashif Salman wrote:
Hello,
Hello,
I have a CGI script; when it runs the very first time I define some variables
my $action = $q-param('action');
The first time it runs, parameter 'action' isn't defined so that is
how I check that it is running the first time and do my things
if ($aciton eq ) {...}
elsif ($action eq submit) {...}
the elsif runs if I hit a button on a form which has a hidden field
that sets action=submit. My question is that the script produces a
warning on the if statement Use of uninitialized value in string eq
.
$ perl -le'
use warnings;
use strict;
my $action;
if ( $action eq ) {
print \$action is empty;
}
'
Use of uninitialized value in string eq at -e line 7.
$action is empty
How can I get rid of that without using no warnings. I tried 'if
(defined($action))' but that still produces a warning.
$ perl -le'
use warnings;
use strict;
my $action;
if ( defined $action ) {
print \$action is empty;
}
'
Use of uninitialized value in string at -e line 7.
$action is empty
You are not testing the variable $action. You are testing a string that
just happens to contain the variable $action. defined() needs to test
the actual variable itself:
if ( defined $action ) {
Also see the FAQ entry:
perldoc -q quoting
John
--
Perl isn't a toolbox, but a small machine shop where you
can special-order certain sorts of tools at low cost and
in short order.-- Larry Wall
--
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
http://learn.perl.org/
Client-Server Architecture script
Dear List I want to write a script using TCP protocol where will be a single server which can handle multiple client request simultaneously. I am able to write a script using IO::Socket but In these scripts my server can handle single client suppose my server is printing the IP address of the client and print 10 times hello world like this But that is not the thing which I want . I need a script which will print the IP address of the client from which it receives the request and also execute the request which it is receiving from the clients. Regarding this if I get u people's help I will be highly obliged. ThanksRegards in advance Anirban Adhikary.
Re: perl warnings
On Mar 17, 2:08 pm, [EMAIL PROTECTED] (Kashif Salman) wrote:
Hello,
I have a CGI script; when it runs the very first time I define some variables
my $action = $q-param('action');
The first time it runs, parameter 'action' isn't defined so that is
how I check that it is running the first time and do my things
if ($aciton eq ) {...}
elsif ($action eq submit) {...}
the elsif runs if I hit a button on a form which has a hidden field
that sets action=submit. My question is that the script produces a
warning on the if statement Use of uninitialized value in string eq
. How can I get rid of that without using no warnings. I tried 'if
(defined($action))' but that still produces a warning.
perldoc -q quoting
Stop double quoting your variables. The warning is telling you that
you're using an uninitialized value in a string. That warning is
important and relevant. It's telling you that it's the *STRING*
you're checking for defined'ness, not the variable within the string.
The string will *always* be defined, regardless of whether or not the
variable is.
if (defined($action)) { ... }
not
if(defined($action)) { ... }
$ perl -wle'
my $foo;
if (defined($foo)) { print 1 yes; } else { print 1 no }
if (defined($foo)) { print 2 yes; } else { print 2 no }
'
Use of uninitialized value in string at -e line 3.
1 yes
2 no
Paul Lalli
--
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
http://learn.perl.org/
Re: perl warnings
On Mar 17, 2:46 pm, [EMAIL PROTECTED] (Gunnar Hjalmarsson) wrote:
Kashif Salman wrote:
I have a CGI script; when it runs the very first time I define some
variables
my $action = $q-param('action');
The first time it runs, parameter 'action' isn't defined so that is
how I check that it is running the first time and do my things
if ($aciton eq ) {...}
elsif ($action eq submit) {...}
the elsif runs if I hit a button on a form which has a hidden field
that sets action=submit. My question is that the script produces a
warning on the if statement Use of uninitialized value in string eq
. How can I get rid of that without using no warnings. I tried 'if
(defined($action))' but that still produces a warning.
if ( ! $action ) {...}
That'll work great until some jackass puts ?action=0 in the URL.
Using defined() is correct. It's what he's passing to defined()
that's not.
Paul Lalli
--
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
http://learn.perl.org/
Re: perl warnings
On Mon, Mar 17, 2008 at 12:04 PM, Paul Lalli [EMAIL PROTECTED] wrote:
On Mar 17, 2:46 pm, [EMAIL PROTECTED] (Gunnar Hjalmarsson) wrote:
Kashif Salman wrote:
I have a CGI script; when it runs the very first time I define some
variables
my $action = $q-param('action');
The first time it runs, parameter 'action' isn't defined so that is
how I check that it is running the first time and do my things
if ($aciton eq ) {...}
elsif ($action eq submit) {...}
the elsif runs if I hit a button on a form which has a hidden field
that sets action=submit. My question is that the script produces a
warning on the if statement Use of uninitialized value in string eq
. How can I get rid of that without using no warnings. I tried 'if
(defined($action))' but that still produces a warning.
if ( ! $action ) {...}
That'll work great until some jackass puts ?action=0 in the URL.
Using defined() is correct. It's what he's passing to defined()
that's not.
Paul Lalli
--
Thank you
--
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
http://learn.perl.org/
Re: xml::twig help
On Mon, Mar 17, 2008 at 9:55 AM, Ken Foskey [EMAIL PROTECTED] wrote:
I am extracting addresses from an XML file to process through other
programs using pipe delimiter the following code works but this is going
to get 130,000 records through it it must be very efficient and I cannot
follow the documentation on the best way to do this.
After this simple one is programmed I have to change a much more complex
version of this program.
#!/usr/bin/perl -w
# vi:set sw=4 ts=4 et cin:
# $Id:$
=head1 SYNOPSIS
Extract addresses from an XML file into pipe delimited file.
usage: address_extract.pl xml_file
=cut
use warnings;
use strict;
use XML::Twig qw(:strict);
sub no_pipe
{
my $value = shift;
$value =~ s/\|//g;
return $value;
}
if( ! -f $ARGV[0] ) {
print $ARGV[0] is not a filename, requires filename as first
parameter!\n;
}
my $sort;
my $sort_file = $ARGV[0].'.unsorted';
unlink $sort_file; # in case of rerun
open( $sort, '', $sort_file )
or die Unable to open $sort_file for output $!;
my $ref = XML::Twig-new( twig_handlers={mem=\member} )
or die Unable to open $ARGV[0] $!;
my $member = 0;
$ref-parsefile( $ARGV[0] );
sub get_value
{
my ($mem_ref, $key) = @_;
my @array = $mem_ref-descendants( $key );
return $array[0]-text();
}
sub member {
my ($t, $mem_ref) = @_;
$member++;
my $mem_no = get_value( $mem_ref, 'member' );
my $add1 = get_value( $mem_ref, 'add1' );
my $add2 = get_value( $mem_ref, 'add2' );
my $add3 = get_value( $mem_ref, 'add3' );
my $suburb = get_value( $mem_ref, 'suburb' );
my $state = get_value( $mem_ref, 'state' );
my $pcode = get_value( $mem_ref, 'pcode' );
print $sort join( '|', $member,
$mem_no,
no_pipe( $add1 ),
no_pipe( $add2 ),
no_pipe( $add3 ),
no_pipe( $suburb),
$state,
$pcode,
) .\n;
return 1;
}
Ken,
If you're really worried about performance, then I would say two
places to look first would be all the temporary variables and
subroutine invocations. I don't know the ins and outs of XML::Twig, so
I don't really have any concrete advice--for instance, does
'$mem_ref-descendants( $key )-text()' work? some modules will parse
a structure like that, some won't--but in general, think about
creative ways you might use map to avoid three subroutine invocations
and (5? 6?) temporary variables for each element you process.
Something like the following should get you started down the path:
## Untested!
sub member {
my $t = shift;
print join |,
map { s/\|//g }
map { $_[0]-descendants( $_ )-text() } qw/ member add1 add2 add3
suburb state pcode /;
}
That may not work out of the box depending on how deeply nested
XML::Twig's refs are, but hopefully you an see where I'm headed with
it.
Also, string concatenation is less efficient than adding another term
to prints argument list. i.e.: use ',' instead of '.' in print when
you can. and lastly, efficiency for matching is, IME, largely a matter
of system configuration and specific input data, but it's worth
benchmarking to see if substr() performs better than s/// in your
case. Sometimes you can get significant savings that way. sometimes
you can't, of course.
HTH,
-- jay
--
This email and attachment(s): [ ] blogable; [ x ] ask first; [ ]
private and confidential
daggerquill [at] gmail [dot] com
http://www.tuaw.com http://www.downloadsquad.com http://www.engatiki.org
values of β will give rise to dom!
flock - exclusive file locking
Hi, I have a cgi script that writes to a disk file. It would be safest if I can get an exclusive lock on the file. I had a look at the opentut and believe I have followed that the example there. Here's what I have sysopen my $fh, $file_path, O_WRONLY || die can't open $file_path: $!\n; flock($fh,LOCK_EX) or die can't lock $file_path: $!\n; seek($fh, 0, 2); # Append to file print $fh $status.\n; print STDERR $0: $! $?\n; close($fh); I am getting the error Inappropriate ioctl for device 0 The worst part about this problem is that it seems completely erratic. Sometimes the string is written to the file and sometimes not. Sometimes I get an error and sometimes not but it never dies and the user will think the data has been written to file! Does anyone see something wrong with the snippet above or have any insights on file-clocking they could offer. Thanx, Dp.
Re: flock - exclusive file locking
Dermot schreef: sysopen my $fh, $file_path, O_WRONLY || die can't open $file_path: $!\n; Change or-operator (or use parenthesis). -- Affijn, Ruud Gewoon is een tijger. -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] http://learn.perl.org/
Re: flock - exclusive file locking
Dermot wrote: I have a cgi script that writes to a disk file. It would be safest if I can get an exclusive lock on the file. I had a look at the opentut and believe I have followed that the example there. Here's what I have sysopen my $fh, $file_path, O_WRONLY || die can't open $file_path: $!\n; flock($fh,LOCK_EX) or die can't lock $file_path: $!\n; seek($fh, 0, 2); # Append to file print $fh $status.\n; print STDERR $0: $! $?\n; close($fh); I am getting the error Inappropriate ioctl for device 0 Even if I can't reproduce that error, I see one thing that is not correct. sysopen my $fh, $file_path, O_WRONLY || die ... That is interpreted as sysopen my $fh, $file_path, (O_WRONLY || die ... ) i.e. the script will never die at that line, since the constant O_WRONLY is always true. You need to do either sysopen( my $fh, $file_path, O_WRONLY ) || die ... ---^--^ or sysopen my $fh, $file_path, O_WRONLY or die ... -^^ -- Gunnar Hjalmarsson Email: http://www.gunnar.cc/cgi-bin/contact.pl -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] http://learn.perl.org/
Re: xml::twig help
From: Ken Foskey [EMAIL PROTECTED]
I am extracting addresses from an XML file to process through other
programs using pipe delimiter the following code works but this is going
to get 130,000 records through it it must be very efficient and I cannot
follow the documentation on the best way to do this.
After this simple one is programmed I have to change a much more complex
version of this program.
snipped
my $ref = XML::Twig-new( twig_handlers={mem=\member} )
or die Unable to open $ARGV[0] $!;
my $member = 0;
$ref-parsefile( $ARGV[0] );
sub get_value
{
my ($mem_ref, $key) = @_;
my @array = $mem_ref-descendants( $key );
return $array[0]-text();
}
sub member {
my ($t, $mem_ref) = @_;
$member++;
my $mem_no = get_value( $mem_ref, 'member' );
my $add1 = get_value( $mem_ref, 'add1' );
my $add2 = get_value( $mem_ref, 'add2' );
my $add3 = get_value( $mem_ref, 'add3' );
my $suburb = get_value( $mem_ref, 'suburb' );
my $state = get_value( $mem_ref, 'state' );
my $pcode = get_value( $mem_ref, 'pcode' );
print $sort join( '|', $member,
$mem_no,
no_pipe( $add1 ),
no_pipe( $add2 ),
no_pipe( $add3 ),
no_pipe( $suburb),
$state,
$pcode,
) .\n;
return 1;
}
Looks like a perfect task for XML::Rules:
#!/usr/bin/perl
use strict;
use XML::Rules;
my $member;
my $parser = XML::Rules-new(
stripspaces = 7,
rules = {
_default = 'content',
mem = sub {
print join( '|', ++$member, map {(my $s = $_[1]-{$_})
=~ s/\|//;
$s} qw(member add1 add2 add3 suburb state pcode)), \n;
return;
}
},
);
$parser-parse(\*DATA);
__DATA__
root
mem
membermember/member
add1add1/add1
add2add2/add2
add3add3/add3
suburbsuburb/suburb
statestate/state
pcodepcode/pcode
/mem
mem
memberother/member
add1ADD1/add1
add2ADD2/add2
add3ADD3/add3
suburbsuburb 2/suburb
statestate/state
pcodepcode/pcode
/mem
/root
I would expect this to be quicker than your XML::Twig solution,
though I have to leave the benchmarking to you.
HTH, Jenda
= [EMAIL PROTECTED] === http://Jenda.Krynicky.cz =
When it comes to wine, women and song, wizards are allowed
to get drunk and croon as much as they like.
-- Terry Pratchett in Sourcery
--
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
http://learn.perl.org/
Re: perl warnings
Paul Lalli wrote:
On Mar 17, 2:46 pm, [EMAIL PROTECTED] (Gunnar Hjalmarsson) wrote:
if ( ! $action ) {...}
That'll work great until some jackass puts ?action=0 in the URL.
So what? If you put random crap in the URL, you can't reasonably expect
a meaningful response.
In this case, if I understand it correctly, the default version of the
page, with a form, would appear. Why would that be a problem for anybody
but the stupid user? ;-)
That said, I agree that using defined() is more to the point.
--
Gunnar Hjalmarsson
Email: http://www.gunnar.cc/cgi-bin/contact.pl
--
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
http://learn.perl.org/
Re: flock - exclusive file locking
Dermot wrote: Hi, Hello, I have a cgi script that writes to a disk file. It would be safest if I can get an exclusive lock on the file. I had a look at the opentut and believe I have followed that the example there. Here's what I have sysopen my $fh, $file_path, O_WRONLY || die can't open $file_path: $!\n; You are using the high precedence '||' operator which means that O_WRONLY is ORed with die() before sysopen() is called and since O_WRONLY is probably always true then die() will *never* be called. You intend to append to the file so you should probably also include O_APPEND with the third argument. You want to either use parentheses: sysopen( my $fh, $file_path, O_WRONLY | O_APPEND ) || die can't open $file_path: $!\n; Or use the low precedence 'or' operator: sysopen my $fh, $file_path, O_WRONLY | O_APPEND or die can't open $file_path: $!\n; flock($fh,LOCK_EX) or die can't lock $file_path: $!\n; seek($fh, 0, 2); # Append to file It looks like you are using the Fcntl.pm module to get the LOCK_EX macro so you should use it to get the SEEK_END macro as well. And since you are using sysopen() to open the file you should use sysseek() instead of seek() sysseek $fh, 0, SEEK_END or die can't seek on $file_path: $!\n; Although you don't really need to do this if you use O_APPEND with sysopen(). print $fh $status.\n; print STDERR $0: $! $?\n; It makes no sense to print the values of $! or $? unless *an* *error* *actually* *occured*. Without an actual error the values in them will be meaningless. close($fh); I am getting the error Inappropriate ioctl for device 0 That error message is not listed in perldiag.pod so it is not a Perl error/warning and it doesn't match any of the error messages in your code above so something other than your Perl program is producing it. perldoc perldiag The worst part about this problem is that it seems completely erratic. Sometimes the string is written to the file and sometimes not. Sometimes I get an error and sometimes not but it never dies and the user will think the data has been written to file! Does anyone see something wrong with the snippet above or have any insights on file-clocking they could offer. perldoc -q lock John -- Perl isn't a toolbox, but a small machine shop where you can special-order certain sorts of tools at low cost and in short order.-- Larry Wall -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] http://learn.perl.org/
FW: How to install Date::Manip on cygwin perl?
Hmm... I did not see this appear on the list so I'm posting it again. I'm using cygwin perl on windows and as you can see below, cpan seems to choking on the path name /cygdrive/c/Documents and settings/a-siehei/My Documents because of the spaces. Surely someone else has a workaround! My apologies if this appears twice. Siegfried From: Siegfried Heintze (Aditi) Sent: Monday, March 17, 2008 12:42 PM To: '[EMAIL PROTECTED]' Subject: How to install Date::Manip on cygwin perl? It looks like the CPAN program does not anticipate paths with spaces in them. I did a google search with no luck. Surely someone has already fixed this problem! How do I fix it? Thanks, Siegfried $ perl -MCPAN -e 'install Date::Manip' CPAN: Storable loaded ok Going to read /cygdrive/c/Documents and Settings/a-siehei/.cpan/Metadata Database was generated on Mon, 17 Mar 2008 10:30:46 GMT Running install for module Date::Manip Running make for S/SB/SBECK/Date-Manip-5.48.tar.gz CPAN: Digest::MD5 loaded ok CPAN: Compress::Zlib loaded ok Checksum for /cygdrive/c/Documents and Settings/a-siehei/.cpan/sources/authors/i d/S/SB/SBECK/Date-Manip-5.48.tar.gz ok Scanning cache /cygdrive/c/Documents and Settings/a-siehei/.cpan/build for sizes sh: /cygdrive/c/Documents: No such file or directory /usr/bin/tar: This does not look like a tar archive /usr/bin/tar: Error exit delayed from previous errors Uncompressed /cygdrive/c/Documents and Settings/a-siehei/.cpan/sources/authors/i d/S/SB/SBECK/Date-Manip-5.48.tar.gz successfully Using Tar:/usr/bin/tar xvf /cygdrive/c/Documents and Settings/a-siehei/.cpan/sou rces/authors/id/S/SB/SBECK/Date-Manip-5.48.tar: /usr/bin/tar: /cygdrive/c/Documents: Cannot open: No such file or directory /usr/bin/tar: Error is not recoverable: exiting now Couldn't untar /cygdrive/c/Documents and Settings/a-siehei/.cpan/sources/authors /id/S/SB/SBECK/Date-Manip-5.48.tar
Re: perl warnings
On 17 Mar 2008, at 21:58, Gunnar Hjalmarsson wrote:
In this case, if I understand it correctly, the default version of
the page, with a form, would appear. Why would that be a problem for
anybody but the stupid user? ;-)
Fundamentally, don't make it possible for your users to do anything to
surprise you.
It would have been a benign surprise this time, once these bad habits
become entrenched it will only be a matter of time before you get a
nasty surprise.
Case in point:
I once wrote some indexing code, things being what they were I had to
make fairly efficient use of disk space. I decided on a simple bit-
packing scheme, so each byte could flag the existence of a word in up
to 8 objects. With sparse files, this was quite efficient indeed.
Somewhere in the code I had a check like this:
if (! $index_byte ) {
[ code to process the next byte ]
}
else {
[ process this byte ]
}
Seems pretty bulletproof doesn't it? If the index byte is empty then
we skip on to the next byte, as we don't have any entries at all for
those 8 objects.
Testing showed a problem occasionally index entries were missing.
A lot of digging found the culprit if you have a scalar byte
holding 8 bits worth of data, it's not just when it holds 0x00 that
that test is true - it's also when it holds 0x30 - ascii '0'.
ALWAYS make your tests as specific as possible, and care about the
exceptions.
- Justin
--
Justin Hawkins
[EMAIL PROTECTED]
http://hawkins.id.au/~justin/
--
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
http://learn.perl.org/
RE: How to install Date::Manip on cygwin perl?
Greetings, I am not familiar at all with Perl, but from my experiences with MS-DOS, if you want to have the CLI read something, IE file name or path, then you need to enclose the filename and path in quotes. So if you could try to enclose the path in quotes, that may work. Regards, Mike Wohlrab www.mikewohlrab.com -Original Message- From: Siegfried Heintze (Aditi) [mailto:[EMAIL PROTECTED] Sent: Monday, March 17, 2008 6:34 PM To: beginners@perl.org Subject: FW: How to install Date::Manip on cygwin perl? Hmm... I did not see this appear on the list so I'm posting it again. I'm using cygwin perl on windows and as you can see below, cpan seems to choking on the path name /cygdrive/c/Documents and settings/a-siehei/My Documents because of the spaces. Surely someone else has a workaround! My apologies if this appears twice. Siegfried From: Siegfried Heintze (Aditi) Sent: Monday, March 17, 2008 12:42 PM To: '[EMAIL PROTECTED]' Subject: How to install Date::Manip on cygwin perl? It looks like the CPAN program does not anticipate paths with spaces in them. I did a google search with no luck. Surely someone has already fixed this problem! How do I fix it? Thanks, Siegfried $ perl -MCPAN -e 'install Date::Manip' CPAN: Storable loaded ok Going to read /cygdrive/c/Documents and Settings/a-siehei/.cpan/Metadata Database was generated on Mon, 17 Mar 2008 10:30:46 GMT Running install for module Date::Manip Running make for S/SB/SBECK/Date-Manip-5.48.tar.gz CPAN: Digest::MD5 loaded ok CPAN: Compress::Zlib loaded ok Checksum for /cygdrive/c/Documents and Settings/a-siehei/.cpan/sources/authors/i d/S/SB/SBECK/Date-Manip-5.48.tar.gz ok Scanning cache /cygdrive/c/Documents and Settings/a-siehei/.cpan/build for sizes sh: /cygdrive/c/Documents: No such file or directory /usr/bin/tar: This does not look like a tar archive /usr/bin/tar: Error exit delayed from previous errors Uncompressed /cygdrive/c/Documents and Settings/a-siehei/.cpan/sources/authors/i d/S/SB/SBECK/Date-Manip-5.48.tar.gz successfully Using Tar:/usr/bin/tar xvf /cygdrive/c/Documents and Settings/a-siehei/.cpan/sou rces/authors/id/S/SB/SBECK/Date-Manip-5.48.tar: /usr/bin/tar: /cygdrive/c/Documents: Cannot open: No such file or directory /usr/bin/tar: Error is not recoverable: exiting now Couldn't untar /cygdrive/c/Documents and Settings/a-siehei/.cpan/sources/authors /id/S/SB/SBECK/Date-Manip-5.48.tar -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] http://learn.perl.org/
Re: while reading 'mastering perl' @+ and @-, not too clear on this
Say you have the string abcdefghi.
The positions in the string are:
a b c d e f g h i
^ ^ ^ ^ ^ ^ ^ ^ ^ ^
0 1 2 3 4 5 6 7 8 9
If you have the regular expression:
/(de)/
Then the match starts at position 3, moves forward two characters, and
ends at position 5, where the next match, if any, will start.
If it stopped at position 4 then it would only match 1 character.
If you want to explore all the gory details of regular expressions
then get the book _Mastering Regular Expression_ by Jeffrey E. F. Friedl:
http://www.oreilly.com/catalog/regex3/index.html
John
Hi, John
Took your advice and start to read 'Mastering regular expression' by
Jeffrey E.F.Friedl,
Can you explain below further?
on page, 205
push(@fields, $+) while $text =~ m{
([^\\\]*(?:\\.[^\\\]*)*),? #standard quoted string(with
possible comma)
| ([^,]+),? #or up to next comman(with
possible comma)
| ,
}gx;
I am not totally understanding how the first line is matching standard
quoted string.
I understand in beginning and end and option ,? at the very end.
now why --- [^\\\]* , should read anything except \ and and \\ ?
why?
and then followed by pretty much samething(in grouping only option ?:)
followed by \\ ?? and samething?
How is that suppose to match quoted string? such as hi, how are you,
Also, how does this work?
defined($1) ? $1 : $3;This ternary reads if $1 is true, then test to
see if $1 is defined? IF $1 is not true, then $3 is defined?(or ??)
--
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
http://learn.perl.org/
\Q on an pattern containing double quotes, braces etc.
Dear Folks,
I want to comment out certain lines in a file that match a particular pattern.
The file contains lines with characters like: {, }, ==, and . Specifically, I
want to replace lines beginning with
ATTRS{idVendor}==07b4, ATTRS{idProduct}==0109,
with
# ATTRS{idVendor}==07b4, ATTRS{idProduct}==0109,
I have been unsuccessful in including the pattern as above and have had to work
around using just the two number patterns like so:
#!/usr/bin/perl -i.bak -pl
use warnings;
use strict;
m/07b4/ and m/0109/ and s/$_/# $_/;
This works, but leaves me wondering how I could include the full pattern,
including metacharacters. Using \Q did not help, but perhaps I was doing
something wrong.
I have included some sample lines that can be used as an input file.
ATTRS{idVendor}==0553, ATTRS{idProduct}==0202, MODE=0660, GROUP=plugdev
ATTRS{idVendor}==06bd, ATTRS{idProduct}==0403, MODE=0660, GROUP=plugdev
ATTRS{idVendor}==07b4, ATTRS{idProduct}==0109, MODE=0660, GROUP=plugdev
ATTRS{idVendor}==06bd, ATTRS{idProduct}==0404, MODE=0660, GROUP=plugdev
ATTRS{idVendor}==04fc, ATTRS{idProduct}==504b, MODE=0660, GROUP=plugdev
ATTRS{idVendor}==07b4, ATTRS{idProduct}==0100, MODE=0660, GROUP=plugdev
ATTRS{idVendor}==07b4, ATTRS{idProduct}==0105, MODE=0660, GROUP=plugdev
ATTRS{idVendor}==07b4, ATTRS{idProduct}==0114, MODE=0660, GROUP=plugdev
ATTRS{idVendor}==07b4, ATTRS{idProduct}==0114, MODE=0660, GROUP=plugdev
ATTRS{idVendor}==07b4, ATTRS{idProduct}==0109, MODE=0660, GROUP=plugdev
ATTRS{idVendor}==07b4, ATTRS{idProduct}==0105, MODE=0660, GROUP=plugdev
Thanks.
Chandra
--
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
http://learn.perl.org/
Re: \Q on an pattern containing double quotes, braces etc.
R (Chandra) Chandrasekhar wrote:
Dear Folks,
Hello,
I want to comment out certain lines in a file that match a particular
pattern. The file contains lines with characters like: {, }, ==, and .
'{' is only special in a regular expression if it is immediately
followed by a numerical digit, for example '{7}' is special whereas
'{abc}' is not. '}' is not special unless it is part of '{numerical
digits}'. '=' and '' are never special in a regular expression.
Specifically, I want to replace lines beginning with
ATTRS{idVendor}==07b4, ATTRS{idProduct}==0109,
There is nothing in that that needs to be escaped.
with
# ATTRS{idVendor}==07b4, ATTRS{idProduct}==0109,
I have been unsuccessful in including the pattern as above and have had
to work around using just the two number patterns like so:
#!/usr/bin/perl -i.bak -pl
use warnings;
use strict;
m/07b4/ and m/0109/ and s/$_/# $_/;
Use s/^/# /; instead of s/$_/# $_/;.
This works, but leaves me wondering how I could include the full
pattern, including metacharacters. Using \Q did not help, but perhaps I
was doing something wrong.
I have included some sample lines that can be used as an input file.
ATTRS{idVendor}==0553, ATTRS{idProduct}==0202, MODE=0660,
GROUP=plugdev
$ perl -Mre=debug -wle'my $x = qr/ATTRS{idVendor}==0553,
ATTRS{idProduct}==0202, MODE=0660, GROUP=plugdev/'
Freeing REx: `,'
Compiling REx `ATTRS{idVendor}==0553, ATTRS{idProduct}==0202,
MODE=0660, GROUP=plugdev'
size 22 Got 180 bytes for offset annotations.
first at 1
1: EXACT ATTRS{idVendor}==0553, ATTRS{idProduct}==0202,
MODE=066...(22)
22: END(0)
anchored ATTRS{idVendor}==0553, ATTRS{idProduct}==0202,
MODE=0660, GROUP=plugdev at 0 (checking anchored isall) minlen 79
Offsets: [22]
1[79] 0[0] 0[0] 0[0] 0[0] 0[0] 0[0] 0[0] 0[0] 0[0] 0[0] 0[0]
0[0] 0[0] 0[0] 0[0] 0[0] 0[0] 0[0] 0[0] 0[0] 80[0]
Freeing REx: `ATTRS{idVendor}==\0553\, ATTRS{idProduct}==\0202\,
MODE..'
Nope, nothing in there that needs to be escaped.
John
--
Perl isn't a toolbox, but a small machine shop where you
can special-order certain sorts of tools at low cost and
in short order.-- Larry Wall
--
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
http://learn.perl.org/
