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Match string in multi-line file

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Laurent_R
Veteran / Moderator

Dec 31, 2012, 7:59 AM

Post #26 of 35 (3941 views)

Re: [Stefanik] Match string in multi-line file [In reply to]	Can't Post

It should match. If it doesn't match, then you probably don't have what you think in your variable and you should try to print it.

Test of the regex under the debugger:

Code

  DB<1> $c = "TRANSID,valueNeeded" 
 
  DB<2> print $2 if $c =~ /^(TRANSID),(\w+)/; 
valueNeeded 
  DB<3> print "$1\n$2" if $c =~ /^(TRANSID),(\w+)/; 
TRANSID 
valueNeeded

As you can see, the regex does match the expression.

Stefanik
User

Jan 3, 2013, 1:32 PM

Post #27 of 35 (3905 views)

Re: [Laurent_R] Match string in multi-line file [In reply to]	Can't Post

Thanks Laurent, I'll check.

Chris Charley
User

Jan 3, 2013, 3:43 PM

Post #28 of 35 (3897 views)

Re: [Stefanik] Match string in multi-line file [In reply to]	Can't Post

Try changing this line

my $value1 = $2 if $FileTemp =~ /^(TRANSID),(\w+)/;

to

my $value1;
$value1 = $2 if $FileTemp =~ /^(TRANSID),(\w+)/m;

(This post was edited by Chris Charley on Jan 3, 2013, 3:45 PM)

BillKSmith
Veteran

Jan 3, 2013, 8:09 PM

Post #29 of 35 (3888 views)

Re: [Chris Charley] Match string in multi-line file [In reply to]	Can't Post

Chris is certainly correct, but some explanation is needed. Editing multi-line files is a bit tricky. Finding perl's documentation of this flag is challenging and the result disappointing ("m Treat string as multiple lines." Refer: perldoc perlop). The book "Perl Best Practices" has a detailed explanation of this issue. The meat of it is that /m changes the meaning of the meta-characters ^ and $ to refer to the start/end of a line rather than the start/end of the string. (The book recommends always using the flags /xms)
Good Luck,
Bill

Laurent_R
Veteran / Moderator

Jan 3, 2013, 11:50 PM

Post #30 of 35 (3877 views)

Re: [Chris Charley] Match string in multi-line file [In reply to]	Can't Post

Hmmm, granted, the /m flag will not do any harm here, but I do not see how it will be useful here. So far, except perhaps for a post title which might be misunderstood, there is nothing in this post to tell us that we have a multiline string at hand.

BillKSmith
Veteran

Jan 4, 2013, 5:17 AM

Post #31 of 35 (3872 views)

Re: [Laurent_R] Match string in multi-line file [In reply to]	Can't Post

Note the code in post 25.

Code

while ($FileTemp = <PARSEFILE>){  
$FileTemp =~ s/:/\n/g;

The string is made into a multi-line string by changing the colons to newlines. We know that there are multiple colons from the file format in post 1.

UPDATE: The following code and output was added to this post to demonstrate the solution:

Code

use strict; 
use warnings; 
*PARSEFILE = *DATA; 
while (my $FileTemp = <PARSEFILE>){ 
    $FileTemp =~ s/:/\n/g; 
    my $value1 = $2 if $FileTemp =~ /^(TRANSID),(\w+)/m; 
    print "The value of $1 is '$value1'\n" if defined $value1; 
} 
__DATA__ 
newline1:FieldCostant1,value1:FieldCostant2,value2:FieldCostant3,value3 
newline4:FieldCostant1,value1:TRANSID,valueNeeded:FieldCostant3,value3 
newline2:FieldCostant1,value1:FieldCostant2,value2:FieldCostant3,value3 
newline3:FieldCostant1,value1:FieldCostant2,value2:FieldCostant3,value3

Output:

Code

The value of TRANSID is 'valueNeeded'

Good Luck,
Bill

(This post was edited by BillKSmith on Jan 4, 2013, 6:07 AM)

Laurent_R
Veteran / Moderator

Jan 4, 2013, 9:54 AM

Post #32 of 35 (3861 views)

Re: [BillKSmith] Match string in multi-line file [In reply to]	Can't Post

In Reply To

Note the code in post 25.

Code

while ($FileTemp = <PARSEFILE>){  
$FileTemp =~ s/:/\n/g;

The string is made into a multi-line string by changing the colons to newlines. We know that there are multiple colons from the file format in post 1.

Right, I forgot that.

Stefanik
User

Jan 4, 2013, 1:08 PM

Post #33 of 35 (3849 views)

Re: [Chris Charley] Match string in multi-line file [In reply to]	Can't Post

Chris what you suggest me works fine.

But I'm not sure about the problem of "/string/m" , Billk talks about.

Laurent_R
Veteran / Moderator

Jan 4, 2013, 4:10 PM

Post #34 of 35 (3843 views)

Re: [Stefanik] Match string in multi-line file [In reply to]	Can't Post

If it works fine for ou, forget about the rest of the discussion.

Wink

BillKSmith
Veteran

Jan 4, 2013, 5:38 PM

Post #35 of 35 (3838 views)

Re: [Stefanik] Match string in multi-line file [In reply to]	Can't Post

In post 29, I tried to explain why Chris's fix works. I consider perl's documentation of this issue very poor. I guess that I did not do any better, Sorry about that.

The update in my later post is the key part of your code with Chris's fix added. It is a complete program that anyone can run to prove that the fix works. It does not introduce any new ideas.
Good Luck,
Bill

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