Re: reading a few bytes into a file

Scott Haneda wrote:
Hello, I have this small C app that someone wrote for me ages ago, and
am tired of it breaking every time I move it around to various
systems, I will include it below.

I am hoping I can do this in perl, as a one liner, were it will read a
the first 4 bytes of a file, grab 4 bytes out of the file, which is a
big endian value, and return that as an int to me.

Here is the basic C app I have been using:

#include <stdio.h>
#include <libkern/OSByteOrder.h>

int main (int argc, char *argv[]) {
FILE* fd;
char buffer[8];
unsigned long int dv;

//open the file
fd = fopen(argv[1], "r");
printf("Filename: %-50s", argv[1]);

fread(buffer, 1, sizeof(buffer), fd);
dv = OSReadBigInt32(buffer, 4);

// print the decimal value
printf(" Value: %ld\n", dv);

return 0;
}


How about this?

Rob



use strict;
use warnings;

my $file = shift;

open my $fh, '<', $file or die $!;
print "Filename: $file";

my $buffer;
my $count = read $fh, $buffer, 4 or die $!;
die "Insufficient data in file" unless $count >= 4;

my $dv = unpack 'N', $buffer;
print " Value: $dv\n";
.

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