[SOLVED] Perl: Save output into file

eminempark · 09-12-2013, 01:11 AM

I would like to ask for help. I have a perl script to do a task (e.g. printf). I would like to read a text.txt which contains ID and x value. And I would like to save the output of printf into a new file. Any help?
So far, I have program until this stage, but it fails.

Code:

open (DATA, "<text.txt");
my $th = 0.000;
for ($th=0; $th<=5; $th+=0.001)
{
 sysopen (FILE, "0_"+$th+"_text.txt", O_RDWR | O_CREAT);
 while(<DATA>){
  my($ID, $x) = split;
  if ($x >= $th)
  {
   printf FILE "%D\n", $ID;
  }
 }
 close(FILE);
}
close(DATA);

It gives me two type errors:

Code:

1. Filehandle FILE opened only for input at the "printf FILE "%D\n", $ID;"
2. Argument "O_SVWST" isn't numeric in sysopen at " sysopen (FILE, "0_"+$th+"_text.txt", O_RDWR | O_CREAT);"

Please help me. Thanks alot!

druuna · 09-12-2013, 01:51 AM

Have a look at this simple example (open infile, write line to outfile):

Code:

#!/usr/bin/perl
use strict ;
use warnings ;

# open file for reading
open( INFILE, "<infile" )
  or die "Can't open infile : $!\n" ;

# open file for writing
open( OUTFILE, ">outfile" )
  or die "Can't open outfile : $!\n" ;

# do your stuff here
while ( <INFILE> ) {
  printf OUTFILE "%D\n", $_ ;
}

# close both filehandles
close( OUTFILE ) ;
close( INFILE ) ;

exit 0 ;

eminempark · 09-12-2013, 02:55 AM

I would like to ask about the output file name. For example, I would like to name my file output from the variable $th. How can I do that? Because from the code that you provided, it can work if we already have the output file. But if we want to automatic create and based on the variable $th? Thank you very much.

druuna · 09-12-2013, 03:11 AM

Quote:

Originally Posted by eminempark

I would like to ask about the output file name. For example, I would like to name my file output from the variable $th. How can I do that?

Quote:

But if we want to automatic create and based on the variable $th?

Code:

#!/usr/bin/perl
use strict ;
use warnings ;

my $outfile = "/path/to/my.outfile" ;

open( INFILE, "<infile" )   # use hard coded file name
  or die "Can't open infile : $!\n" ;

open( OUTFILE, ">$outfile" )   # use variable instead of hard coded
  or die "Can't open $outfile : $!\n" ;

while ( <INFILE> ) {
  printf OUTFILE "%D\n", $_ ;
}

close( OUTFILE ) ;
close( INFILE ) ;

exit 0 ;

The above overwrites the outfile (single >), if you want/need to append to the outfile then use >> instead of >
open( OUTFILE, ">>$outfile" )

Quote:

Because from the code that you provided, it can work if we already have the output file.

Nope, that isn't true. output will be created if it isn't there:

Code:

$ ls -l
total 8
-rwxr-x--- 1 druuna druuna 280 sep 12 08:49 foo.pl
-rw-r----- 1 druuna druuna   6 sep 12 08:45 infile
$ ./foo.pl 
$ ls -l
total 12
-rwxr-x--- 1 druuna druuna 280 sep 12 08:49 foo.pl
-rw-r----- 1 druuna druuna   6 sep 12 08:45 infile
-rw-r----- 1 druuna druuna   6 sep 12 10:00 outfile

These might come in hand:
Perl:

pan64 · 09-12-2013, 04:00 AM

what do you mean by $th ? there is no such variable in perl. Do you want to specify the output file as an argument to the program?

Firerat · 09-12-2013, 04:05 AM

from OP

Code:

my $th = 0.000;
for ($th=0; $th<=5; $th+=0.001)

pan64 · 09-12-2013, 04:10 AM

oh, yes, you need to construct the filename like:
$outfile = "0_" . $th . "_text.txt";

eminempark · 09-12-2013, 04:38 AM

May I know why are some my file name can be so weird? It is very long...

My code is some sort like this

Code:

#!/usr/bin/perl
use strict;
#use warnings;
my $th;
my $file_number;
for ($th=22.063; $th<=28.813; $th+=0.001)
{
open(INPUT, "<burst.txt")
  or die "Cant open infile :$!\n";
  
open(OUTPUT, "+>0_".$th."_burst.txt")
  or die "Cant open outfile :$!\n";
  

  while(<INPUT>){
    my($ID, $x) = split;
    my $vector = $x;
    if ($ID == 1 || $ID == 600)
    {
      printf OUTPUT "%d %.3f\n", $ID, $x;
    }
    else
    {
      if($vector >= $th)
      {
        printf OUTPUT "%d %.3f\n", $ID, $x;
      }
    }
  }
  close(OUTPUT);
}
close(INPUT);

exit 0;

Any idea?

pan64 · 09-12-2013, 04:40 AM

you should open (and close) the file inside the while loop.

eminempark · 09-12-2013, 05:41 AM

You mean the INPUT file or OUTPUT file or both?

pan64 · 09-12-2013, 06:40 AM

you have only one input file that should be opened only once - that will happen before the while loop.
You have a lot of output files, all of them should be opened inside the loop - when you know the name

eminempark · 09-17-2013, 02:19 AM

Quote:

Originally Posted by pan64

you have only one input file that should be opened only once - that will happen before the while loop.
You have a lot of output files, all of them should be opened inside the loop - when you know the name

It still produce the same file name. With alot 0 behind. any solution for this? I really need help.

pan64 · 09-17-2013, 02:31 AM

try:
$outputfile = sprintf "0_%1.3f_burst.txt", $th;
open(OUTPUT, "+>$outputfile") or die "Cant open outfile :$!\n";

eminempark · 09-17-2013, 02:56 AM

After I change to this code

Code:

#!/usr/bin/perl
use strict;
#use warnings;
my $th;
for ($th=22.000; $th<=22.005; $th+=0.001)
{
open(INPUT, "<burst.txt")
  or die "Cant open infile :$!\n";
  while(<INPUT>){
  my $outputfile = sprintf "0_%.3f_burst.txt", $th;
  open(OUTPUT, "+>$outputfile")
  or die "Cant open outfile :$!\n"; 
    my($ID, $x) = split;
    #my $vector = $x;
    if ($ID == 1 || $ID == 600)
    {
      printf OUTPUT "%d %.3f\n", $ID, $x;
    }
    else
    {
      if($x >= $th)
      {
        printf OUTPUT "%d %.3f\n", $ID, $x;
      }
    }
      close(OUTPUT);
  }

}
close(INPUT);

it unable to process the data correctly. It will only print out ID 600. It will not even print out ID 1.Why?

pan64 · 09-17-2013, 03:50 AM

we have still no info about the data you want to handle. please uncomment the line #use warnings and fix problems. Also you may need to check if split was successful.
"unable to process" is not enough to help you, please specify what have you got and what did you expect.