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Full Discussion: Need to pass variable in a command and assign value to a variable
Top Forums UNIX for Beginners Questions & Answers Need to pass variable in a command and assign value to a variable Post 302999728 by bakunin on Tuesday 27th of June 2017 05:19:24 AM
Old 06-27-2017
Quote:
Originally Posted by ektubbe
I am trying below command to be passed in a shell script, header_date_14 is a variable and $1 is the name of a file I intend to pass as a command line argument, however command line argument is not being accepted.
You should never NEVER use constructs like $1 directly in your code. You see, $1, $2, etc. are positional parameters, not variables. $1 isn't the name of a variable just happening to have the name "1", like "$foo", it is the first parameter passed to this specific context - and what "this specific context" means can change (and does so) from context to context.

Therefore instead of doing:

Code:
var=$( command $1 )

do it like this:

Code:
argument1=$1
argument2=$2

...

var=$( command $argument1 $argument2 )

This also gives you the opportunity to give a meaningful name to the variable like "inputfile", instead of "$1", which won't tell you by its name what it is supposed to contain.

I hope this helps.

bakunin
 

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LEARN ABOUT MOJAVE

scope

scope(n)							    [incr Tcl]								  scope(n)

__________________________________________________________________________________________________________________________________________________

NAME

       scope - capture the namespace context for a variable

SYNOPSIS

       itcl::scope name
_________________________________________________________________

DESCRIPTION

       Creates	a scoped value for the specified name, which must be a variable name.  If the name is an instance variable, then the scope command
       returns a string of the following form:
	      @itcl object varName
       This is recognized in any context as an instance variable belonging to object.  So with itcl3.0 and beyond, it is possible to use  instance
       variables in conjunction with widgets.  For example, if you have an object with a private variable x, and you can use x in conjunction with
       the -textvariable option of an entry widget.  Before itcl3.0, only common variables could be used in this manner.

       If the name is not an instance variable, then it must be a common variable or a global variable.  In that case, the scope  command  returns
       the fully qualified name of the variable, e.g., ::foo::bar::x.

       If the name is not recognized as a variable, the scope command returns an error.

       Ordinary  variable  names  refer to variables in the global namespace.  A scoped value captures a variable name together with its namespace
       context in a way that allows it to be referenced properly later.  It is needed, for example, to wrap up variable names when a Tk widget	is
       used within a namespace:
	      namespace foo {
		  private variable mode 1

		  radiobutton .rb1 -text "Mode #1"	   -variable [scope mode] -value 1
		  pack .rb1

		  radiobutton .rb2 -text "Mode #2"	   -variable [scope mode] -value 2
		  pack .rb2
	      }
       Radiobuttons .rb1 and .rb2 interact via the variable "mode" contained in the namespace "foo".  The scope command guarantees this by return-
       ing the fully qualified variable name ::foo::mode.

       You should never use the @itcl syntax directly.	For example, it is a bad idea to write code like this:
	      set {@itcl ::fred x} 3
	      puts "value = ${@itcl ::fred x}"
       Instead, you should always use the scope command to generate the variable name dynamically.  Then, you can pass that name to a widget or to
       any other bit of code in your program.

KEYWORDS

       code, namespace, variable

itcl																	  scope(n)
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