script for adding timestamp to stdin

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

Hi,

I can't get the following script to work. I'm probably overlooking something super obvious, but I can't grok it this morning.

What I want to do is have an ongoing log file, where I can enter a comment, and have that comment timestamped. Any tips appreciated.

use strict;
use warnings;
use Data::Dumper;

my ($sec,$min,$hour,$mday,$mon,$year,$wday,
    $yday,$isdst)=localtime(time);


my $table;


my $log = 'log_file.txt';


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

while (<$fh>) {

    my $comment = <STDIN>;
    chomp $comment;

    printf "%4d-%02d-%02d %02d:%02d:%02d\t",
    $year+1900,$mon+1,$mday,$hour,$min,$sec;

    print $comment . "\n";

    printf $fh "%4d-%02d-%02d %02d:%02d:%02d\t",
    $year+1900,$mon+1,$mday,$hour,$min,$sec;

    print $fh $comment . "\n";

}

close $fh;
[download]

Comment on script for adding timestamp to stdin Download Code

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Re: script for adding timestamp to stdin by Old_Gray_Bear (Bishop) on Jun 02, 2010 at 17:21 UTC
You opened the file for append (with `'>>'`) and then use it as input (`while (<$fh>) {`), which gives you and immediate EOF.... ---- I Go Back to Sleep, Now. OGB	[reply] [d/l] [select]
Re: script for adding timestamp to stdin by vtheron (Novice) on Jun 02, 2010 at 18:10 UTC
You're looping on input from your log file. I expect that you meant to loop on input from STDIN. Also, you need to update your timestamp variables inside the loop. Try this: `use strict; use warnings; use Data::Dumper; my $table; my $log = 'log_file.txt'; open my $fh, '>>', $log or die "Can't open $log : $!"; while (<STDIN>) { my $comment = $_; chomp $comment; my ($sec,$min,$hour,$mday,$mon,$year,$wday, $yday,$isdst)=localtime(time); printf "%4d-%02d-%02d %02d:%02d:%02d\t", $year+1900,$mon+1,$mday,$hour,$min,$sec; print $comment . "\n"; printf $fh "%4d-%02d-%02d %02d:%02d:%02d\t", $year+1900,$mon+1,$mday,$hour,$min,$sec; print $fh $comment . "\n"; } close $fh;` [download]	[reply] [d/l]
Re^2: script for adding timestamp to stdin by Anonymous Monk on Jun 02, 2010 at 18:42 UTC
thanks -- but the log file is not being updated still... why is that? We have a file handle, we're printing to it... er...	[reply]
Re^3: script for adding timestamp to stdin by almut (Canon) on Jun 02, 2010 at 19:10 UTC
Try `open my $fh, ... use IO::Handle; $fh->autoflush(); # <--` [download] File handles are block-buffered by default, i.e. output is not flushed/written to the file until the buffer is full.	[reply] [d/l]
Re^4: script for adding timestamp to stdin by Anonymous Monk on Jan 20, 2012 at 15:45 UTC
Re: script for adding timestamp to stdin by almut (Canon) on Jun 02, 2010 at 17:33 UTC
What I want to do is have an ongoing log file, ... What exactly is the intention, i.e. why are you trying to read/write from/to the end of the same file? Why the reading?	[reply]