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Select lines in a file between pattern

tsdjim
New User

Aug 28, 2017, 10:13 AM

Post #1 of 6 (3122 views)

Select lines in a file between pattern	Can't Post

I have a file myfile which has text between patterns for each month.

For example:

Auguststart
Some text
some more text
Augustend
Septemberstart
Some text
some more text
Septemberend

For example for August it should select the text between Auguststart and Augustend but the if statement does not select anything in my code below.

$random_file = '/mydir/myfile';
my ( $day, $month, $year ) = ( localtime )[3,4,5];
$month = (
qw/ January February March
April May June
July August September
October November December /
)[$month];

$monthx = $month . 'start';
$monthy = $month . 'end';
open(SESAME, $random_file);
while (<SESAME>) {
if (/^$monthx/../^$monthy/)
{print SESAME};

}
close (SESAME) or die "Could not close sample.txt: $!";

BillKSmith
Veteran

Aug 28, 2017, 11:33 AM

Post #2 of 6 (3118 views)

Re: [tsdjim] Select lines in a file between pattern [In reply to]	Can't Post

There is nothing wrong with your logic. If you had used strict and warnings, you would have received an error message referring to the offending statement. (Your print statement is trying to print back to the input file.)

I have replaced your disk file with an in-memory file in order to show the data in the post.

Code

C:\Users\Bill\forums\guru>type tsdjim0.pl 
my $random_file = \<<'END_RANDOM_FILE'; 
Auguststart 
Some text 
some more text 
Augustend 
Septemberstart 
Some text 
some more text 
Septemberend 
END_RANDOM_FILE 
my ( $day, $month, $year ) = ( localtime )[3,4,5]; 
$month = ( 
 qw/ January February March 
 April May June 
 July August September 
 October November December / 
)[$month]; 
 
$monthx = $month . 'start'; 
$monthy = $month . 'end'; 
open(SESAME, '<', $random_file); 
while (<SESAME>) { 
 if (/^$monthx/../^$monthy/) 
{print }; 
 
 } 
 close (SESAME) or die "Could not close sample.txt: $!"; 
 
 
C:\Users\Bill\forums\guru>perl tsdjim0.pl 
Auguststart 
Some text 
some more text 
Augustend

I recommend several changes to improve the style.

Always use strict and warnings

Always use three-argument form of open

Always check open for failure.

Always use lexical (my) file-handles

Format your code with perltidy

Here is an improved version of your code:

Code

use strict; 
use warnings; 
 
my $random_file = \<<'END_RANDOM_FILE'; 
Auguststart  
Some text  
some more text  
Augustend  
Septemberstart  
Some text  
some more text  
Septemberend  
END_RANDOM_FILE 
 
my $month = (qw/ 
    January February March 
    April   May      June 
    July    August   September 
    October November December / 
)[(localtime)[4]]; 
 
my $monthx = $month . 'start'; 
my $monthy = $month . 'end'; 
open( my $SESAME, '<', $random_file ) or die "Cannot open input file\n:$!"; 
while (<$SESAME>) { 
    print if  /^$monthx/ .. /^$monthy/ ; 
} 
close($SESAME) or die "Could not close sample.txt: $!";

Good Luck,
Bill

tsdjim
New User

Aug 28, 2017, 12:18 PM

Post #3 of 6 (3115 views)

Re: [tsdjim] Select lines in a file between pattern [In reply to]	Can't Post

Thanks Bill, that works great.

How can I exclude the pattern line from the print result.

Ron

Chris Charley
User

Aug 28, 2017, 1:22 PM

Post #4 of 6 (3112 views)

Re: [tsdjim] Select lines in a file between pattern [In reply to]	Can't Post

To exclude the pattern line, say print unless . . .

Code

#!/usr/bin/perl 
use strict; 
use warnings; 
use Time::Piece; 
 
open my $fh, '<', \<<EOF; 
Auguststart 
Some text 
some more text 
Augustend 
Septemberstart 
Some text 
some more text 
Septemberend 
EOF 
 
my $month = localtime->strftime("%B"); 
 
while (<$fh>) {  
    if (/^${month}start$/../^${month}end$/) { 
        print unless /^$month(?:start|end)$/;  
    } 
}

(Note that I used Time::Piece to get the name of the month. It will eliminate the need to enumerate the month names as your and Bill's code does).

(This post was edited by Chris Charley on Sep 3, 2017, 1:40 PM)

BillKSmith
Veteran

Aug 28, 2017, 2:57 PM

Post #5 of 6 (3108 views)

Re: [Chris Charley] Select lines in a file between pattern [In reply to]	Can't Post

Thanks for the note about strftime in Time::Piece. I have always used the copy in POSIX (When I think of it at all).
Good Luck,
Bill

tsdjim
New User

Aug 30, 2017, 10:54 AM

Post #6 of 6 (3084 views)

Re: [BillKSmith] Select lines in a file between pattern [In reply to]	Can't Post

Thanks Bill and Chris for your solution.

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