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Top Forums Shell Programming and Scripting Updating a variable within a variable Post 302994293 by bakunin on Tuesday 21st of March 2017 09:25:33 AM
Old 03-21-2017
Quote:
Originally Posted by rovf
But it might be the case that your colleagues start saying nasty things to you if you are actually doing it in productive code ;-)
Very true! ;-)) eval is the command which sole purpose is to be avoided, so to say.

Quote:
Originally Posted by rovf
Code:
container()
{
   echo "abc${myvar}xyz"
}
myvar=4711
actual_value=$(container)

In a stricter sense this is also problematic. You need to know in the main program, that the variable in container() is named in a certain way (here "myvar"). You could alleviate this dependency by doing:

Code:
container()
{
   echo "abc${1}xyz"
}
myvar=4711
actual_value=$(container $myvar)

 

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variable(n)						       Tcl Built-In Commands						       variable(n)

__________________________________________________________________________________________________________________________________________________

NAME
variable - create and initialize a namespace variable SYNOPSIS
variable ?name value...? name ?value? _________________________________________________________________ DESCRIPTION
This command is normally used within a namespace eval command to create one or more variables within a namespace. Each variable name is initialized with value. The value for the last variable is optional. If a variable name does not exist, it is created. In this case, if value is specified, it is assigned to the newly created variable. If no value is specified, the new variable is left undefined. If the variable already exists, it is set to value if value is specified or left unchanged if no value is given. Normally, name is unqualified (does not include the names of any containing namespaces), and the variable is created in the current namespace. If name includes any namespace qualifiers, the variable is created in the specified names- pace. If the variable is not defined, it will be visible to the namespace which command, but not to the info exists command. If the variable command is executed inside a Tcl procedure, it creates local variables linked to the corresponding namespace variables (and therefore these variables are listed by info vars.) In this way the variable command resembles the global command, although the global command only links to variables in the global namespace. If any values are given, they are used to modify the values of the associated namespace variables. If a namespace variable does not exist, it is created and optionally initialized. A name argument cannot reference an element within an array. Instead, name should reference the entire array, and the initialization value should be left off. After the variable has been declared, elements within the array can be set using ordinary set or array commands. EXAMPLES
Create a variable in a namespace: namespace eval foo { variable bar 12345 } Create an array in a namespace: namespace eval someNS { variable someAry array set someAry { someName someValue otherName otherValue } } Access variables in namespaces from a procedure: namespace eval foo { proc spong {} { # Variable in this namespace variable bar puts "bar is $bar" # Variable in another namespace variable ::someNS::someAry parray someAry } } SEE ALSO
global(n), namespace(n), upvar(n) KEYWORDS
global, namespace, procedure, variable Tcl 8.0 variable(n)
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