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Top Forums Shell Programming and Scripting not null cheking of an argument in perl Post 302120246 by vino on Tuesday 5th of June 2007 08:42:59 AM
Old 06-05-2007
A couple of ways to do this.
Code:
VAR=
if [ -z "${VAR}" ] ; then
  echo "VAR contains nothing"
fi

or

Code:
VAR=
if [ x"${VAR}" = x ] ; then
  echo "VAR contains nothing"
fi


edit: My bad. I did not notice that you asked for it in perl

Last edited by vino; 06-05-2007 at 10:03 AM..
 

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UPSLOG(8)							    NUT Manual								 UPSLOG(8)

NAME
upslog - UPS status logger SYNOPSIS
upslog -h upslog [OPTIONS] DESCRIPTION
upslog is a daemon that will poll a UPS at periodic intervals, fetch the variables that interest you, format them, and write them to a file. The default format string includes variables that are supported by many common UPS models. See the description below to make your own. OPTIONS
-h Display the help message. -f format Monitor the UPS using this format string. Be sure to enclose format in quotes so your shell doesn't split it up. Valid escapes within this string are: %% Insert a single "%" %TIME format% Insert the time with strftime formatting %ETIME% Insert the number of seconds, ala time_t. This is now a 10 digit number. %HOST% insert the local hostname %UPSHOST% insert the host of the UPS being monitored %PID% insert the pid of upslog %VAR varname% insert the value of variable varname The default format string is: %TIME @Y@m@d @H@M@S% %VAR battery.charge% %VAR input.voltage% %VAR ups.load% [%VAR ups.status%] %VAR ups.temperature% %VAR input.frequency% -i interval Wait this many seconds between polls. This defaults to 30 seconds. If you require tighter timing, you should write your own logger using the upsclient(3) library. -l logfile Store the results in this file. You can use "-" for stdout, but upslog will remain in the foreground. -s ups Monitor this UPS. The format for this option is upsname[@hostname[:port]]. The default hostname is "localhost". -u username If started as root, upsmon will setuid(2) to the user id associated with username for security. If username is not defined, it will use the value that was compiled into the program. This defaults to "nobody", which is less than ideal. SERVICE DELAYS
The interval value is merely the number given to sleep(3) after running through the format string. Therefore, a query will actually take slightly longer than the interval, depending on the speed of your system. LOG ROTATION
upslog writes its PID to upslog.pid, and will reopen the log file if you send it a SIGHUP. This allows it to keep running when the log is rotated by an external program. SEE ALSO
Server: upsd(8) Clients: upsc(8), upscmd(8), upsrw(8), upsmon(8) Internet resources: The NUT (Network UPS Tools) home page: http://www.networkupstools.org/ Network UPS Tools 05/21/2012 UPSLOG(8)
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