PERL: how to tell if variable is NULL Post: 34878

10 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

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

2. Shell Programming and Scripting

check for NULL variable

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

3. Shell Programming and Scripting

test Null variable

hi forum i beginning with script and i want test un null variable in a schell i just don t know the syntax here is a litle example y=test echo $y unset y echo $y (so here Y = Null) if Y=Null then echo "y is null" exit fi

4. Shell Programming and Scripting

not null cheking of an argument in perl

Hi, I have to check whether an argument say $ARGV is not null in an if operator. Please let me know the operator. It would be great if you write a psuedo code. Thanks in advance Ammu

5. Shell Programming and Scripting

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.

6. Shell Programming and Scripting

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...

7. Shell Programming and Scripting

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

Hello, Unix-forums! My problem: read -p "Enter any number, please" number sleep 1 echo $number | tr -d 0-9 test -z $number && echo "Thank you" || echo "This is not a number"Test always displays "This is not a number". It doesn't matter if I entered a or 1. But if I order echo...

8. Shell Programming and Scripting

Checking for null condition in a UNIX variable

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 ...

9. Shell Programming and Scripting

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

10. Shell Programming and Scripting

If grep value is null then assign 0 to variable

LEARN ABOUT REDHAT

usual

usual(n)							     [incr Tk]								  usual(n)

NAME

       usual - access default option-handling commands
	    for a mega-widget component

SYNOPSIS

       usual ?tag? ?commands?

DESCRIPTION

       The  usual  command  is	used outside of an [incr Tcl] class definition to define the usual set of option-handling commands for a component
       widget.	Option-handling commands are used when a component is registered with the Archetype base class via the "itk_component add" method.
       They  specify  how  the component's configuration options should be integrated into the composite option list for the mega-widget.  Options
       can be kept, renamed, or ignored, as described in the Archetype man page.

       It is tedious to include the same declarations again and again whenever components are added.  The usual command  allows  a  standard  code
       fragment to be registered for each widget class, which is used by default to handle the options.  All of the standard Tk widgets have usual
       declarations defined in the [incr Tk] library.  Similar usual declarations should be created whenever a new mega-widget class is conceived.
       Only the most-generic options should be included in the usual declaration.

       The  tag  name  is  usually the name of a widget class, which starts with a capital letter; however, any string registered here can be used
       later with the usual command described on the Archetype man page.

       If the commands argument is specified, it is associated with the tag string, and can be accessed later via itk_component add.

       If only the tag argument is specified, this command looks for an existing tag name and returns the commands associated with it.	 If  there
       are no commands associated with tag, this command returns the null string.

       If no arguments are specified, this command returns a list of all tag names previously registered.

EXAMPLE

       Following is the usual declaration for the standard Tk button widget: usual Button {
	   keep -background -cursor -foreground -font
	   keep -activebackground -activeforeground -disabledforeground
	   keep -highlightcolor -highlightthickness
	   rename  -highlightbackground -background background Background } Only the options that would be common to all buttons in a single mega-
       widget are kept or renamed.  Options like "-text" that would be unique to a particular button are ignored.

KEYWORDS

       itk, Archetype, component, mega-widget

itk									3.0								  usual(n)

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