Some time ago I wrote the code below to sort my crontab file by
time (see sub compare_crons for the sorting criteria). It's
very crude, but it could work as a starting point for reading
a crontab file in memory. Once you read it in, you can make
any changes, write it to a new file, an run the crontab command
on it.
This program leaves in each element of @db an array reference
containing the 5 time fields, and a text element containing
the current line, together with any comments that came before
it. Of course, for making any modifications, this second element
would have to be split further.
eval 'exec perl -x $0 ${1+"$@"}' # -*-perl-*-
if 0;
#!perl -w
# Sort a crontab by time
# Each entry (possibly commented) is moved as a block with all the
# comment lines before it.
# Diego Zamboni, March 21, 2001. Happy Spring!
use strict;
use vars qw($curblock $tf @fields @db);
# Regex for a time field in crontab, which can be a number, sequence o
+f numbers
# or an asterisk
$tf='(?:[*]|(?:\d+(?:-\d+)?)(?:,\d+(?:-\d+)?)*)';
while (<>) {
$curblock.=$_;
if (@fields=(/^\#?($tf)\s+($tf)\s+($tf)\s+($tf)\s+($tf)\s+(.*)/)) {
push @db, [[@fields], $curblock];
$curblock="";
}
}
foreach (sort compare_crons @db) {
print "$_->[1]";
warn "-----------\n" . join(" | ", @{$_->[0]})."\n";
}
# compare by month, day, hour and minute. Ignore weekday
sub compare_crons {
my @fa=@{$a->[0]};
my @fb=@{$b->[0]};
return compare_tf($fa[3],$fb[3]) ||
compare_tf($fa[2],$fb[2]) ||
compare_tf($fa[1],$fb[1]) ||
compare_tf($fa[0],$fb[0]);
}
# Compare two cron fields. Asterisk considered as zero, otherwise
# compare by the first number
sub compare_tf {
my ($na,$nb);
$na=($_[0]=~/^(\d*)/)[0]||0;
$nb=($_[1]=~/^(\d*)/)[0]||0;
return ($na <=> $nb);
}
--ZZamboni
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