Some help with my project:

[0uts1de]

Hi monks,i am quite new in perl programming (only 2 weeks learning)and i have a question about my script, the idea is that the script prints some things about a choosen filesystem and gives the avalible space, the used space, the type, etc.

All sounds good, but when I run my script it returns a error ("Illegal division by zero at analizer (16-1-17).pl line 35, <STDIN> line 1.") and I dont know how to fix it or what is working bad, the code is this: (NOTE: I am spanish so i write the comments in my lenguaje, sorry if u dont understand it but i dont think is necesary a traduction)

    #!usr/bin/perl
    #solo funciona para unix/linux/solaris(solaris ni idea)
    #si da el error "Undefined subroutine &main::SYS_statfs called at 
+Filesys/DiskSpace.pm at line XXX", editar syscall.ph
    # (en el perl lib tree) y copiar la linea "SYS_statfs {196;}" fuer
+a del "if (defined &__hp9000s800)" (alrededor de la linea 356)
    use strict ;
    use warnings ;
    use Filesys::DiskSpace ;
    use POSIX ;
    #sistema de archivos/particion a comprobar espacio
    #sacar fecha ;
    my $TIME = strftime("%d/%m/%Y %H:%M:%S", localtime(time) ) ;
    print "+----------+---+----------+\n" ;
    print "+Script made up by 0uts1de+\n" ;
    print "+----------+---+----------+\n" ;
    print "Today is $TIME \n" ;
    print "Write the filesystem/partiton you want to monitor, for exam
+ple /home or /usr \n" ;
    my $monit = <STDIN> ;
    chomp $monit ;
    print "##warning level is by default about a 20 % of free space, i
+f u want to change this##\n" ;
    print "##change the variable warn in the script with a editor like
+ vim or gedit ##\n" ;
    ########## warn string ############
    my $warn = 10 ;
    ###################################
    #consegir caracteristicas de la particion/filesystem (raw)
    my ($fs_type, $fs_desc, $used, $avail, $fused, $favail) = df $moni
+t ;
    my $monit_percentual = (  $avail  /  $avail+$used  ) * 100 ;
    my $final_used = $used / 1000 ;
    my $final_avail = $avail / 1000 ;
    print "$monit is a $fs_type filesystem who has $final_used space u
+sed (in MB) and $final_avail of avalible space (in MB too) \n" ;
    #comparacion con el porcentaje de $monit_percentual
    if ($monit_percentual < $warn) {
            print "Less of the $warn % of the space of the filesystem 
+$monit is avalible for use, consider uninstall unused software \n" ;
    }
    elsif ($monit_percentual eq $warn) {
            print "Be carefull, exactly the $warn % of the space of $m
+onit is usable, consider uninstall unused software \n" ;
    }
    else {
            print "There is a $monit_percentual % of avarible space of
+ the disk \n" ;
    }

In the imput I have the error and the rest, here is:

+----------+---+----------+
+Script made up by 0uts1de+
+----------+---+----------+
Today is 16/01/2017 16:31:04 
Write the filesystem/partiton you want to monitor, for example /home o
+r /usr 
/
##warning level is by default about a 20 % of free space, if u want to
+ change this##
##change the variable warn in the script with a editor like vim or ged
+it ##
Illegal division by zero at analizador de filesystem (16-1-17).pl line
+ 35, <STDIN> line 1.

Thanks in advance!

[toolic]

This is the only line that could generate that message (although it doesn't look like line 35):

my $monit_percentual = (  $avail  /  $avail+$used  ) * 100 ;

UPDATE (dave_the_m): That means $avail is probably 0 ($avail+$used)=0 (probably both variables are 0). Tip #2 from the Basic debugging checklist: print

Also:

• How do I compose an effective node title?
• Filesys::DiskSpace looks like it may have been abandoned. It has several open issues, and the last update was more than 17 years ago.

[dave_the_m]

That means ($avail+$used)=0

Due to precedence, it actually means $avail is zero. The OP probably meant to write

my $monit_percentual = (  $avail  /  ($avail+$used)  ) * 100 ;

Dave.

[0uts1de]

I read both comments and the problem was that the module FileSys::DiskSpace is quite old and abandoned as sayed toolic, and is not able to read modern filesystems as ext4 or ext3, i am using now the Sys::Filesystem module to do the same work, and for the moment is working.

Thanks both for the replies

[madtoperl]

In this code also if you add one more if condition before doing this calculation,
it will prevent these kind of error if future

if ($used){ 
my $monit_percentual = (  $avail  /  $avail+$used  ) * 100 ;
    my $final_used = $used / 1000 ;
    my $final_avail = $avail / 1000 ;
    print "$monit is a $fs_type filesystem who has $final_used space u
+sed (in MB) and $final_avail of avalible space (in MB too) \n" ;
    #comparacion con el porcentaje de $monit_percentual
    if ($monit_percentual < $warn) {
            print "Less of the $warn % of the space of the filesystem 
+$monit is avalible for use, consider uninstall unused software \n" ;
    }
    elsif ($monit_percentual eq $warn) {
            print "Be carefull, exactly the $warn % of the space of $m
+onit is usable, consider uninstall unused software \n" ;
    }
    else {
            print "There is a $monit_percentual % of avarible space of
+ the disk \n" ;
    }
}else{
print "Some message\n";
}

[marto]

my $monit_percentual = (  $avail  /  $avail+$used  ) * 100 ;

"it will prevent these kind of error if future"

If you want to prevent errors be aware of perlop "Operator precedence and associativity".

use strict;
use warnings;

my $avail = 1;
my $used  = 1;

my $testa = ( $avail / $avail + $used ) * 100;
my $testb = ( $avail / ( $avail + $used ) ) * 100;

print "testa: $testa\ntestb: $testb\n";