Run script when server load is below threshold written in Perl.

Server_load.pl

# FOUND ON http://www.skolnick.org/cgi-bin/list.pl?file=serverload.pl
#
#!/usr/bin/perl -w 
# serverload.pl 
# Subroutine to defer execution if server load is high 
# dhs 09/20/02 
# 
# Subroutine is written to be called from a script run as a cron 
# job where specific execution time is much less important than 
# not impacting server performance 
# &serverload( $number_of_attempts, $time_between_attempts, $load_threshold ) 
# 
# $number_of_attempts: the number of times to check for low server 
# load before execution (default 10) 
# 
# $time_between_attempts: the number of seconds to wait between attempts 
# (default 30) 
# 
# $load_threshold: the one-minute server load above which execution 
# will not take place (default 6.0) 
# 
# serverload returns 1 if load is okay (proceed) or 0 if load is high 

## test code 
if ( &serverload( 10, 30, 6.0 ) ) { 
  print "okay! \n"; 
} else { 
  print "wait 'til later! \n"; 
} 

sub serverload( $attempts, $wait, $threshold ) { 
  my $LOAD_TOO_HIGH = 0; 
  my $GO_AHEAD = 1; 
  my $return_value = $LOAD_TOO_HIGH; 
  my ( $attempts, $wait, $threshold ) = @_; 
  my $load; 
  unless ( $attempts ) { $attempts = 10; } 
  unless ( $wait ) { $wait = 30; } 
  unless ( $threshold ) { $threshold = 6.0; } 
  for ( my $i = 0; $i < $attempts; $i++ ) { 
#    print "."; ## test code 
    $load = &loadnow(); 
    if ( $load <= $threshold ) { 
      $return_value = $GO_AHEAD; 
      last; 
    } else { 
      sleep( $wait ); 
    } 
  } 
#  print " $load \n";  ## test code 
  return $return_value; 
} 

sub loadnow { 
  open( LOAD, "/proc/loadavg" ) 
    or die "Bad juju! serverload couldn't open /proc/loadavg: $! \n"; 
  my $load_avg = <LOAD>; 
  close LOAD; 
  my ( $one_min_avg ) = split /\s/, $load_avg; 
  return $one_min_avg; 
}