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Full Discussion: Perl - backticks v system in if statements
Top Forums Shell Programming and Scripting Perl - backticks v system in if statements Post 79446 by Unbeliever on Thursday 28th of July 2005 04:31:54 AM
Old 07-28-2005
In the first example: system('/bin/date');

prints the date to STDOUT and returns the exit status of /bin/date, in this case '0'. So the following if condition fails. You have already printed out the date simply by calling system('/bin/date').

In the second example `/bin/date' returns the string that you get by running the command but doesnt print anything to STDOUT. Since any non null string (except for the string that contains just '0') evaluates to true in perl your if clause prints 'Cant get date'.

At a rough guess its the second way you want to use but like this:

Code:
sub getDate
{
  my $date;
  print "start date\n";
  $date=`/bin/date`;
  if ( !$date )
  {
    print "can't get date\n";
    exit(2);
  }
  print $date;
  print "finish date\n";
}

 

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LEARN ABOUT DEBIAN

netsds::util::datetime

NetSDS::Util::DateTime(3pm)				User Contributed Perl Documentation			       NetSDS::Util::DateTime(3pm)

NAME

       NetSDS::Util::DateTime - common date/time processing routines

SYNOPSIS

	       use NetSDS::Util::DateTime;

	       print "Current date: " . date_now();

DESCRIPTION

       This package provides set of routines for date and time processing.

EXPORTED FUNCTIONS

       date_now_array([TIME])
	   Returns array of date items for given date.	If source date is not set current date used.

       date_now([TIME])
	   Return [given] date as string.

	       2001-12-23 14:39:53

       date_now_iso8601([TIME])
	   Return date as ISO 8601 string.

	       20011223T14:39:53Z

	   <http://en.wikipedia.org/wiki/ISO_8601> http://www.w3.org/TR/NOTE-datetime <http://www.w3.org/TR/NOTE-datetime>

       date_strip(DATE)
	   Trim miliseconds from date.

       date_date(DATE)
	   Trim time part from date.

       date_time(DATE)
	   Trim date part from date.

       time_from_string($string)
	   Return parsed date/time structure.

       date_from_string($string)
	   Return date from string representation.

       date_inc([INCREMENT, [TIME]])
	   Return date incremented with given number of seconds.

       date_inc_string([INCREMENT, [TIME]])
	   Return string representation of date incremented with given number of seconds.

EXAMPLES

       None yet

BUGS

       Unknown yet

SEE ALSO

       Date::Parse, Date::Format

TODO

       Import stuff from Wono project

AUTHOR

       Valentyn Solomko <val@pere.org.ua>

       Michael Bochkaryov <misha@rattler.kiev.ua>

perl v5.12.4							    2011-08-27					       NetSDS::Util::DateTime(3pm)
All times are GMT -4. The time now is 03:17 PM.
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