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search string for a text file

bgolivar
Novice

Mar 4, 2012, 8:14 AM

Post #1 of 12 (1273 views)

search string for a text file	Can't Post

#
#
# print "Enter File Name to Open:\n";

# $filename = "Temp2.txt";

#$filename = "TestBed_DeviceLog.txt";
chomp (my $filename = <STDIN>);
my $find = "DeviceUnderTestString";

open (MYFILE, "$filename") || die "Can't Open file: $!\n";

@InputLine = <MYFILE>;

print "Line that matched $find\n";

for (@InputLine) {
if ($_ =~ /$find/) {
print "$_";
}
}

# $linecntr = 0;

# print @InputLine;

I think this may have been posted before and for that I apologize. However, I need some help with a script that reads a large text file for a string and output the results to a file.
What I have works okay enough minus the output to a text file part. Also, is there a way to read the file line by line rather than loading the file in memory in case the file is very large.

Thanks for the help

FishMonger
Veteran

Mar 4, 2012, 10:01 AM

Post #2 of 12 (1268 views)

Re: [bgolivar] search string for a text file [In reply to]	Can't Post

There are a number if issues I could point out, but will direct my initial comments to base question.

You should use a while block to loop over the file.

Code

while ( my $line = <MYFILE> ) {

If you want to output the matches to a file, then you'll want to open a write filehandle and print to that filehandle instead of STDOUT.

You may want to look at using the grep function instead of using the while or for loop.

(This post was edited by FishMonger on Mar 4, 2012, 10:02 AM)

rovf
Veteran

Mar 5, 2012, 4:52 AM

Post #3 of 12 (1252 views)

Re: [bgolivar] search string for a text file [In reply to]	Can't Post

What FishMonger said, is technically correct. However, I would read from STDIN and write to STDOUT and use redirection to specify the files. In this way, your program will be more flexible. After all, you are writing kind of a specific "fgrep".

Having said this, I wonder why you roll out your own program and don't use fgrep instead (which is available on all major operating systems).

bgolivar
Novice

Mar 5, 2012, 7:14 AM

Post #4 of 12 (1250 views)

Re: [rovf] search string for a text file [In reply to]	Can't Post

Thanks for the tip on fgrep. I'll look into this and will post my update. Thanks...stay tuned.

bgolivar
Novice

Mar 16, 2012, 5:14 PM

Post #5 of 12 (1153 views)

Re: [bgolivar] search string for a text file [In reply to]	Can't Post

Changed it a bit, baby steps at a time. I wanted to be able to read a large file line by line so here's what I tried:

#simply reading a file line by line

use strict;
use warnings;

print"Enter the File you want to search.\n";
print"> ";

chomp (my $filename = <STDIN>);

open (MYINPUTFILE, "$filename");
while (<MYINPUTFILE>)
{

# good practice to store $_ value because
# subsequent operations may change it

my ($line) = $_;

# print the line to the screen
print "$line\n";

}

It worked well enough. Now, I wan't to try to search for the specific string as I originally wanted. Should be easy enough. I looked into the fgrep as mentioned but opted to go this route.

I am actually trying to expand on this script to pull data based on the search criteria. The search is the starting point but the actual data are several lines above the searched string. I'll come back to that later. But thank you thus far for the useful hints.

bgolivar
Novice

Mar 17, 2012, 9:37 AM

Post #6 of 12 (1123 views)

Re: [bgolivar] search string for a text file [In reply to]	Can't Post

Current script:

use strict;
use warnings;

print"Enter the File you want to search.\n";
print"> ";
chomp (my $filename = <STDIN>);

print"Enter the search string:\n";
print"> ";
chomp (my $find = <STDIN>);

open (MYINPUTFILE, "$filename");

while (<MYINPUTFILE>)
{
my @inputline = <MYINPUTFILE>;

# good practice to store $_ value because
# subsequent operations may change it
for (@inputline) {
if ($_=~/$find/){
open (MYOUTPUTFILE, ">$_");
}
}
}

Now when I run the script, it comes back with "Name "main::MYOUTPUTFILE" used only once: possible typo at C:\Bryan\Perl\Temp\Op
enFile_003.pl line 31." Help!

naven8
Novice

Mar 17, 2012, 11:16 AM

Post #7 of 12 (1121 views)

Re: [bgolivar] search string for a text file [In reply to]	Can't Post

If you want to read the file and grep for some specific pattern then you can use following code. You code is so confusing.I am not sure why you are reading entire file in while loop. (my @inputline = <MYINPUTFILE>; )

Replace your while loop with following code and try the results.

Code

open my $FH,'>',"output.txt" || die "Unable to open output.txt File $!"; 
 
while (<MYINPUTFILE>){ 
   if(/$find/){ 
      print $FH "$_\n"; 
    } 
}

The following code will create multiple files.

Code

if ($_=~/$find/){  
  open (MYOUTPUTFILE, ">$_");  
} 
}

If this didn't solve your problem then Please provide your actual requirement.

(This post was edited by naven8 on Mar 17, 2012, 11:20 AM)

FishMonger
Veteran

Mar 17, 2012, 12:43 PM

Post #8 of 12 (1115 views)

Re: [bgolivar] search string for a text file [In reply to]	Can't Post

Code

use strict; 
use warnings; 
 
print "Enter the File you want to search.\n" . '> ', 
chomp (my $filename = <STDIN>); 
 
print "Enter the search string:\n" . '> '; 
chomp (my $find = <STDIN>); 
 
open my $in_fh, '<', $filename or die "failed to open '$filename' <$!>"; 
 
my $outfile = 'output.txt'; 
open my $out_fh, '>', $outfile or die "failed to open '$outfile' <$!>"; 
 
print {$out_fh} grep(/$find/, <$in_fh>); 
 
close $in_fh; 
close $out_fh;

(This post was edited by FishMonger on Mar 17, 2012, 12:48 PM)

bgolivar
Novice

Mar 17, 2012, 1:06 PM

Post #9 of 12 (1110 views)

Re: [FishMonger] search string for a text file [In reply to]	Can't Post

This worked out perfectly, thank you very much.

bgolivar
Novice

Mar 17, 2012, 1:43 PM

Post #10 of 12 (1107 views)

Re: [naven8] search string for a text file [In reply to]	Can't Post

I read the entire file in the while loop because some of the files can be a couple of gigs in size, ran into a problem with that before.

FishMonger
Veteran

Mar 17, 2012, 2:00 PM

Post #11 of 12 (1105 views)

Re: [bgolivar] search string for a text file [In reply to]	Can't Post

In Reply To

I read the entire file in the while loop because some of the files can be a couple of gigs in size, ran into a problem with that before.

The first line of your while loop slurped the entire file into an array, which is exactly what you were trying to avoid, but failed.

bgolivar
Novice

Mar 17, 2012, 2:05 PM

Post #12 of 12 (1103 views)

Re: [FishMonger] search string for a text file [In reply to]	Can't Post

Right. I removed that line in the previous version.

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