masala_curry has asked for the wisdom of the Perl Monks concerning the following question:

Hello,

I have a C program say cProg.c that asks the user to enter a filename, (opens that file and operates over it) and saves the output in a file "output.txt"


I have a PERL script main.pl
I wish to somehow generate the output.txt when I run main.pl

I am using vi editor to do all this and my university already has all the required compilers, interpreters etc...

For easier understanding, lets say this is how the C file looks like:
==============cProg.c===================== 
#include< stdio.h>
main (int argc, char *argv[])
{
        FILE *fp;
        if (argc!= 2)
                printf ("Please Enter a FileName\n");
        else
        {
                fp = fopen (argv[1], "r");
                printf ("File Found\n");   
                fclose (fp);
        }
        return 0;
}

[download]

=================cProg.c Ends=================
I compile and run this program this way:
[ ~ ] gcc cProg.c
[ ~ ] ./a.out input.txt > output.txt

This generates output.txt which has "File Found" as its only contents.

Now I wish to write a PERL script which would automatically generate "output.txt" when i execute the PERL script
=================main.pl====================

#!/usr/bin/perl

./a.out input.txt > output.txt   ###How should I do this?

$output_file="output.txt";
open(OP, $output_file) || die("Could not open file!");
@sequence=<OP>;     # tosses the contents of "output.txt" in an array 
+"@sequence" to work on.

[download]
===============mail.pl ENDS====================

Kindly show me the path to heaven =)

Replies are listed 'Best First'.
Re: How to run C object code in PERL
by tilly (Archbishop) on Apr 04, 2009 at 04:18 UTC
    If you want to handle this in Perl the best solution is to not use a temp file at all: 
    #! /usr/bin/perl
use strict;
use warnings;

my $cmd = "./a.out input.txt";
open(my $pipe, "-|", $cmd) or die "Can't run '$cmd': $!";
my @sequence = <$pipe>;
# Proceed to process output.

    [download]
[reply]
[d/l]
      Works like a Charm!
[reply]
Re: How to run C object code in PERL
by gwadej (Chaplain) on Apr 04, 2009 at 04:15 UTC

    There are many ways to solve this. I would probably use system in this case.

    G. Wade
[reply]
Re: How to run C object code in PERL
by Bloodnok (Vicar) on Apr 04, 2009 at 12:55 UTC
    It's not too clear what ###How should I do this? means, but my reading of it suggests that you might be trying to compile & run the C code (c/w writing a perl script to emulate your C code) something along the following lines ... 
    use warnings;
use strict;

system 'gcc cProg.c';
die "Compile failed - $!" if $? >> 8;
system './a.out input.txt > output.txt';
die "Run failed"  if $? >> 8;

    [download]
    I used system, since there is no (apparent) requirement to capture output - only to run the command and continue dependant on the success status.

    Your comment tosses the contents of "output.txt" in an array "@sequence" to work on is only true in the context of a file containing a single line - as in your example.

    If it were a multi-line file, you might want to undef the input record separator ($/ - see perlvar) in order to slurp the file into the array in one operation.

    A user level that continues to overstate my experience :-))
[reply]
[d/l]
[select]
      Thanks a lot tilly and Bloodnok. Both solutions are quite elegant.

      In my problem, I find it convenient to have an output.txt file for later viewing. Also, I need the user to mention the names of input and output files.

      So I would use Bloodnok's solution for my problem.
[reply]

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