PERL: how to tell if variable is NULL Post: 34865

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How to filter a null variable.

I have the necessity to use this command: cat file1 | grep $A | grep $B where sometime A and, or, B are not set. For example: I set A=@ never defined or set B The above command send a cat error. Any idea? Thanks. Giovanni

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check for NULL variable

Hello I want to check for NULL variable.. but this is not working..please help thanks in advance esham

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how to check null variable

korn shell If then update_smartcare_user_password "$u_id" else echo "Not a database user" fi i get this error Syntax error at line *** : `then' is not expected. what should i do. I want to check whether $a is null or not.

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Question on NULL and zero value of variable

Hi all, I have a stupid question on NULL and zero(0). In a script I've been working with, one of the lines is: if && then The problem I seem to have is when $Current_csm2 is null, this if block is not triggered, and I don't get why because I was under the impression that NULL!=0 Can...

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Value of variable is NULL, but test doesn't seem to recognize

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i have this code for i in `cat sql_output.txt` do -- some script commands done sql_output.txt has 1 column with employee_ids If the sql_output.txt is null then the do loop should not execute. How can i implement this. for i in `cat sql_output.txt` If i is null or empty then ...

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If condition to check null variable

Guys, Please help me on the below sample.cfg var=NULL sample.sh #!/bin/sh . /sample.cfg if ;then 1 st command here else 2 nd command here fi

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If grep value is null then assign 0 to variable

LEARN ABOUT DEBIAN

irsend

IRSEND(1)							   User Commands							 IRSEND(1)

NAME

       irsend - basic LIRC program to send infra-red commands

SYNOPSIS

       irsend [options] DIRECTIVE REMOTE CODE [CODE...]

DESCRIPTION

       Asks the lircd daemon to send one or more CIR (Consumer Infra-Red) commands. This is intended for remote control of electronic devices such
       as TV boxes, HiFi sets, etc.

       DIRECTIVE can be:
	  SEND_ONCE	    - send CODE [CODE ...] once
	  SEND_START	    - start repeating CODE
	  SEND_STOP	    - stop repeating CODE
	  LIST		    - list configured remote items
	  SET_TRANSMITTERS  - set transmitters NUM [NUM ...]
	  SIMULATE	    - simulate IR event

       REMOTE is the name of a remote, as described in the lircd configuration file.

       CODE is the name of a remote control key of REMOTE, as it appears in the lircd configuration file.

       NUM is the transmitter number of the hardware device.

       For the LIST DIRECTIVE, REMOTE and/or CODE can be empty:

	  LIST	 ""    ""   - list all configured remote names
	  LIST REMOTE  ""   - list all codes of REMOTE
	  LIST REMOTE CODE  - list only CODE of REMOTE

       The SIMULATE command only works if it has been explicitly enabled in lircd.

       -h --help
	      display usage summary

       -v --version
	      display version

       -d --device
	      use given lircd socket [/var/run/lirc/lircd]

       -a --address=host[:port]
	      connect to lircd at this address

       -# --count=n
	      send command n times

EXAMPLES

	  irsend LIST DenonTuner ""
	  irsend SEND_ONCE  DenonTuner PROG-SCAN
	  irsend SEND_ONCE  OnkyoAmpli VOL-UP VOL-UP VOL-UP VOL-UP
	  irsend SEND_START OnkyoAmpli VOL-DOWN ; sleep 3
	  irsend SEND_STOP  OnkyoAmpli VOL-DOWN
	  irsend SET_TRANSMITTERS 1
	  irsend SET_TRANSMITTERS 1 3 4
	  irsend SIMULATE "0000000000000476 00 OK TECHNISAT_ST3004S"

FILES

       /etc/lirc/lircd.conf
	      Default lircd configuration file.  It should contain all the remotes, their infra-red codes and the corresponding timing	and  wave-
	      form details.

DIAGNOSTICS

       If lircd is not running (or /var/run/lirc/lircd lacks write permissions) irsend aborts with the following diagnostics:
       "irsend: could not connect to socket"
       "irsend: Connection refused" (or "Permission denied").

SEE ALSO

       The documentation for lirc is maintained as html pages. They are located under html/ in the documentation directory.

       lircd(8), mode2(1), smode2(1), xmode2(1), irrecord(1), irw(1), http://www.lirc.org.

irsend 0.9.0-pre1						   October 2010 							 IRSEND(1)

10 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

How to filter a null variable.

Discussion started by: gio123bg

2. Shell Programming and Scripting

check for NULL variable

Discussion started by: esham

3. Shell Programming and Scripting

test Null variable

Discussion started by: kykyboss

4. Shell Programming and Scripting

not null cheking of an argument in perl

Discussion started by: ammu