Perl::Scripts - cronolog

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cronolog is a simple filter program that reads log file entries from standard input and writes each entry to the output file specified by a filename template and the current date and time.

Snippet
Information

cronolog

```
#!/usr/bin/perl
```

# ****************************************************************

```
# file: cronolog
```
```
# date: 2007-08-24 10:35:27
```

# author: Marko Schulz - <info@tuxnet24.de>

```
#
```

# description: cronolog is a simple filter program that reads log

# file entries from standard input and writes each entry to the

# output file specified by a filename template and the current

```
# date and time.
```

# ****************************************************************

```
use strict;
```
```
 
```
```
# define the rotation time (HHMM)...
```
```
my $rotation_time_hhmm="00:00";
```
```
 
```

# load package for command line arguments (GetOptions)...

```
use Getopt::Long;
```
```
 
```

# load package for file handling (dirname)...

```
use File::Basename;
```
```
 
```
```
# define variables...
```

use vars qw( $opt_V $opt_p $opt_s $opt_t $opt_h $file );

```
 
```

# set alarm handler and trigger initial alarm

```
$SIG{ALRM} = \&sig_alarm;
```
```
alarm(1);
```
```
 
```
```
# define command line arguments...
```
```
Getopt::Long::Configure('bundling');
```
```
GetOptions
```

    ( "V"   => \$opt_V, "version"   => \$opt_V,

      "p=s" => \$opt_p, "period=s"  => \$opt_p,

      "t=i" => \$opt_t, "tzone=i"   => \$opt_t,

      "s=s" => \$opt_s, "symlink=s" => \$opt_s,

      "h"   => \$opt_h, "help"      => \$opt_h );

```
 
```

# default time shift is 0 if opt_t is not defined...

```
$opt_t=0 if ( !$opt_t );
```
```
 
```

# ****************************************************************

```
# check cammandline arguments...
```
```
 
```
```
# display help or usage...
```
```
if ( $opt_h ) {
```

    print "<STDIN> | cronolog --symlink|-s /path/to/symlink [ --tzone|-t <time shift> --period|";

    print "-p 1day --help|-h --version|-V ] /path/to/logfile-\%Y-\%m-\%d.log\n\n";

    print "\t--symlink|-s /path/to/symlink (required)\n";

    print "\t--tzone|-t int (-12..+12) (default 0)\n";

    print "\t--period|-p rotation period (ignored, we rotate at 00:00)\n";

    print "\t--help|-h display this screen\n";

    print "\t--version|-V display version\n\n";

```
    exit 0;
```
```
}
```
```
 
```
```
# print out a cronolog version...
```
```
if ( $opt_V ) {
```

    print STDERR "cronolog version 1.7.0\n";

```
    exit 0;
```
```
}
```
```
 
```

# error message if no logfile defined...

```
if ( !$ARGV[-1] ) {
```

    print "cronolog: No logfile defined.\n";

```
    exit 1;
```
```
}
```
```
 
```

# print error message if logfile directory is not writable...

```
if ( ! -w dirname( $ARGV[-1] ) ) {
```

   print "cronolog: Can't create logfile -".$opt_s."- because the directory is not writable.\n";

```
   exit 1;
```
```
}
```
```
 
```
```
# remove leading character...
```
```
$opt_s =~ s/^=//g;
```
```
 
```

# error message if no symlink defined...

```
if ( !$opt_s ) {
```

    print "cronolog: No symlink defined.\n";

```
    exit 1;
```
```
}
```
```
 
```

# print error message if symlink directory is not writable...

```
if ( ! -w dirname( $opt_s ) ) {
```

   print "cronolog: Can't create symlink -".$opt_s."- because the directory is not writable.\n";

```
   exit 1;
```
```
}
```
```
 
```

# ****************************************************************

```
# program action...
```
```
 
```

# let the signal handler run at least once

```
sleep(1);
```
```
 
```
```
# loop until STDIN is closed...
```
```
while (<STDIN>) {
```
```
 
```

	# get current filename from template...

```
	$file=get_filename($ARGV[-1]);
```
```
 
```
```
	# flush buffer...
```
```
	$|=1;
```
```
 
```
```
	# write data from STDIN...
```

	open (DAT, ">>$file") or die( "Can't open -".$file."-: ".$! );

```
    print DAT $_;
```
```
	close(DAT);
```
```
 
```
```
}
```
```
 
```
```
 
```

# ****************************************************************

# return logfile name from logfile template...

```
 
```
```
sub get_filename {
```
```
 
```
```
    my $filename=shift;
```
```
 
```

    # get date as array reference( YYYY, MM, DD, HH, MM, SS )...

```
    my $ref_date = date( $opt_t );
```
```
 
```

    # replace placeholder ( %Y, %m, %d, %H, %M, %S => strftime )...

    $filename =~ s!\%Y!$ref_date->[0]!g;

    $filename =~ s!\%m!$ref_date->[1]!g;

    $filename =~ s!\%d!$ref_date->[2]!g;

    $filename =~ s!\%H!$ref_date->[3]!g;

    $filename =~ s!\%M!$ref_date->[4]!g;

    $filename =~ s!\%S!$ref_date->[5]!g;

```
 
```
```
    return $filename;
```
```
 
```
```
}
```
```
 
```

# ****************************************************************

# signal handler, invoked on SIG_ALRM...

```
 
```
```
sub sig_alarm {
```
```
 
```
```
    # get target file of the symlink...
```
```
    my $symlink=$opt_s;
```
```
    my $target = readlink( $symlink );
```
```
 
```

    # get date as array reference( YYYY, MM, DD, HH, MM, SS )...

```
    my $ref_date = date( $opt_t );
```
```
 
```
```
    # refresh filename to use 
```
```
    $file=get_filename($ARGV[-1]);
```
```
 
```

    # create new file (only) if it does not exist...

    if ( ! -f $file || $ref_date->[3].":".$ref_date->[4] eq $rotation_time_hhmm ) {

```
 
```

        # check if symlink with name of log file exists that would prevent logfile creation

```
        if ( -l $file) {
```
```
 
```

            # remove symlink only if symlink or file exists...

            unlink( "$file" ) or die( "Can't remove symlink -".$file."-: ".$! );

```
        }
```
```
 
```

        # open file in append mode (may have been created from within while loop!)

        open (DAT, ">>$file") or die( "Can't open file -".$file."-: ".$! );

```
        close(DAT);
```
```
    }
```
```
 
```

    # remove symlink if target file and current logfile are not equal or rotation_time is reached...

    if ( $target ne $file || $ref_date->[3].":".$ref_date->[4] eq $rotation_time_hhmm ) {

```
 
```

        # remove symlink only if symlink or file exists...

        unlink( "$symlink" ) or die( "Can't remove symlink -".$symlink."-: ".$! ) if ( -l $symlink || -f $symlink );

```
 
```
```
 
```

        # create symlink to current logfile if no symlink exists...

        symlink( "$file", "$symlink" ) or die( "Can't create symlink -".$symlink."- to -".$file."-: ".$! ) if ( ! -l $symlink );

```
    }
```
```
 
```

    # trigger new alarm to occur when next minute begins ...

```
    my $ref_date = date( $opt_t );
```
```
    alarm( 60-$ref_date->[5] );
```
```
 
```
```
}
```
```
 
```

# ****************************************************************

# return date as array ( %Y, %m, %d, %H, %M, %S => strftime )...

```
 
```
```
sub date {
```
```
 
```
```
    my $tzone=shift;
```

    my ($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) = localtime(time+($tzone*3600));

```
    $year = 1900+$year;
```
```
    $mon = $mon+1;
```
```
 
```
```
    $sec  = sprintf( "%02d", $sec  );
```
```
    $min  = sprintf( "%02d", $min  );
```
```
    $hour = sprintf( "%02d", $hour );
```
```
    $mon  = sprintf( "%02d", $mon  );
```
```
    $mday = sprintf( "%02d", $mday );
```
```
 
```

    my @date=( $year, $mon, $mday, $hour, $min, $sec );

```
    return \@date;
```
```
 
```
```
}
```
```
 
```

# ****************************************************************

```
# end of this script...
```

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