File contents not updated properly

[balakrishnan]

open(FH,">Sample");
$|=1;
while(1) {
print FH "This is for testing\n";
sleep 1;
}
This is to write some contents into the "Sample" file for every 1 second. After running this program, the file "Sample" is not updated.
what is the correction, it requires?

Thanks,
balakrishnan

[dharanivasan]

use strict;
use warnings;
use FileHandle;

open(FH,">Sample");
$|=1;
FH->autoflush(1);
while(1) {
print FH "This is for testing\n";
sleep 1;
}

close(FH);

[sathiya.sw]

You need to select the file handle as,
select(FH);


open(FH,">Sample");
select(FH);
$|=1;
while(1) {
print FH "This is for testing\n";
sleep 1;
}

[fmerges]

Hi,

First of all, don't assume that you could open the file, check for it. Then use 3 argument open, and don't use a typeglob.

open my $fh, '>', $filename or die "Can't open $filename: $!";

The solution provided will leave the default handler to be *FH, which is not desired, meaning all prints, etc will use *FH; alternatives:

# not so maintainable, but still used frequently
select((select($fh), $|++)[0]);

# better
use IO::Handle;
$fh->autoflush(1);

Check out the link about buffering provided...

Regards,

[apl]

You're Suffering from Buffering!

[Dhineshkumar]

Using IO::Handle, We can flush the data whenever we need.
Like below :
use IO::Handle;
open(FH,">Sample");
while(1) {
print FH "This is for testing\n";
FH->flush();
sleep 1;
}

[Dhineshkumar]

When we are execute some commands in perl, Automatically file content got flush.
Like below :
open(FH,">Sample");
while(1) {
print FH "This is for testing\n";
sleep 1;
`date`; -- Sample command
}