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Full Discussion: Tricky array substitution in functions
Top Forums Shell Programming and Scripting Tricky array substitution in functions Post 302255476 by alex_5161 on Thursday 6th of November 2008 01:12:11 PM
Old 11-06-2008
I guess the 'last' acctualy is the 'nr_elements' or you have something missed.

If it is, let see what the 'last' has:

You have build correct string "\${\#$array_name[@]}"; asked to 'eval'uate it - have in result "${#<arr_name>[@]}"; and asking to execute it!
Try execute this line with correct array name: you will have :command not found!
Because it will produce a number of the array elements and a number is not a command by itself.

I did not clear understand what do you need: the correct number of element for any given array or the command itself into a variable?

If the array element number, you do not need to escape the characters in b1 and b2 (acctualy, I do not see why do you need them) :
Code:
b1='${#';
b2='[@]}'
eval echo $b1$array_name$b2

I do not see any reason to build a command itself and after that execute it. It will required double execution, as you already figured it out.

So, you have an array name in a variable and would like to call a function that returns the aray elements number? A function need to be executed to get a result. So:
Code:
>elms(){ eval echo \${\#$1[@]\}; return 0;}

># - checking:
>a1=(aa dd cc rr);
>a2=(klkl ioio opo);
> echo `elms a1`
4
> echo $(elms a2)
3

To get just a "echo $nr_elements" the nr_elements should be a variable, which you could set in a function. So
Code:
>set_elms_n(){ elm_n=$(eval echo \${\#$1[@]\}); return 0;}
>set_elms_n a1
>echo $elm_n;
4
>set_elms_n a2
>echo $elm_n;
3

That what you was looking for?
Last edited by alex_5161; 11-06-2008 at 02:24 PM..
 

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times

times(1)							   User Commands							  times(1)

NAME

       times - shell built-in function to report time usages of the current shell

SYNOPSIS

   sh
       times

   ksh
       times

DESCRIPTION

   sh
       Print the accumulated user and system times for processes run from the shell.

   ksh
       Print the accumulated user and system times for the shell and for processes run from the shell.

       On this man page, ksh(1) commands that are preceded by one or two * (asterisks) are treated specially in the following ways:

	   1.	  Variable assignment lists preceding the command remain in effect when the command completes.

	   2.	  I/O redirections are processed after variable assignments.

	   3.	  Errors cause a script that contains them to abort.

	   4.	  Words, following a command preceded by ** that are in the format of a variable assignment, are expanded with the same rules as a
		  variable assignment. This means that tilde substitution is performed after the = sign and word splitting and file  name  genera-
		  tion are not performed.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Availability		     |SUNWcsu			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       ksh(1), sh(1), time(1), attributes(5)

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