Local variables get corrupted when calling another function.

[calabrra]

Hi,

I'm calling a function from within a function. This causes local variables to be corrupted because they happen to have the same name in the function I am calling.

Is there a workaround to this annoyance without having to rename variables?


Thanks,
-Bob

 

[vgersh99]

pls post your code.

vlad
+----------------------------+
| #include<disclaimer.h> |
+----------------------------+

 

[calabrra]

Hi Vlad,

I got the code to work right by changing &quot;strpos&quot; to &quot;strcol&quot; and &quot;result&quot; to &quot;result_ascii&quot; in the calling function. Nevertheless, I would like to know if there's a cleaner way to preserve parameter values in the calling function without changing parameter names.

Thanks,
-Bob


BEGIN{printf(&quot;Output: %s\n&quot;, hex2ascii(hexnum) );}
END{}

###################################################
function hex2ascii(hex_string)
###################################################

{

#Convert any size hex string to 8-bit ASCII

result_ascii = &quot;&quot;;

strcol = length(hex_string) - 1;

while (strcol > 0)

{

#Capture binary 8-bit chunks starting from right to left
chunk = substr(hex_string, strcol, 2);

#Convert hex to decimal
dec = hex2uint(chunk);

#Convert decimal to ASCII character
digit = sprintf(&quot;%c&quot;, dec);

#Concatenate and resume looping
result_ascii = digit result_ascii;

strcol = strcol - 2;

}

return(result_ascii);

}

###################################################
function hex2uint(hex_string) {
###################################################

# Convert hex string to unsigned integer

result = 0;
power = 0;
MSD = substr (hex_string, 1, 1);

for (strpos = length(hex_string); strpos > 0; strpos--)
{
digit = substr(hex_string, strpos, 1);
if (match(digit, /[a-fA-F]/))
{
gsub(/[aA]/, &quot;10&quot;, digit);
gsub(/[bB]/, &quot;11&quot;, digit);
gsub(/[cC]/, &quot;12&quot;, digit);
gsub(/[dD]/, &quot;13&quot;, digit);
gsub(/[eE]/, &quot;14&quot;, digit);
gsub(/[fF]/, &quot;15&quot;, digit);
}
result = result + digit*(16**power);
power++;
}

return (result);

}

 

[Salem]

AWK has an odd way of declaring local variables - they're listed as additional parameters (which you don't pass obviously).

So it would be

function hex2uint(hex_string,
  result, power, MSD ) {

  result = 0;
  power  = 0;
  MSD = substr (hex_string, 1, 1);

  for (strpos = length(hex_string); strpos > 0; strpos--)
  {
    digit  = substr(hex_string, strpos, 1);
    if (match(digit, /[a-fA-F]/))
    {
      gsub(/[aA]/, "10", digit);
      gsub(/[bB]/, "11", digit);
      gsub(/[cC]/, "12", digit);
      gsub(/[dD]/, "13", digit);
      gsub(/[eE]/, "14", digit);
      gsub(/[fF]/, "15", digit);
    }
    result = result + digit*(16**power);
    power++;
  }

  return (result);

}

--

http://www.catb.org/~esr/faqs/smart-questions.html

 

[vgersh99]

the convention is to declare ALL 'local' function variables in the formal declaration of a function.
If they are NOT declared in the formal declaration of the function, their scope is global.

Also, the convention is to separate the 'passed-in' paramerters from the 'local' variables with spaces:
Here's an example based on your code for the 'called' function - you probably need to do the same to the 'calling' function as well to avoid any global variables contamination:

###################################################
function hex2uint(hex_string, result, power,MSD,strpos,digit) {
###################################################

# Convert hex string to unsigned integer

result = 0;
power = 0;
MSD = substr (hex_string, 1, 1);

for (strpos = length(hex_string); strpos > 0; strpos--)
{
digit = substr(hex_string, strpos, 1);
if (match(digit, /[a-fA-F]/))
{
gsub(/[aA]/, &quot;10&quot;, digit);
gsub(/[bB]/, &quot;11&quot;, digit);
gsub(/[cC]/, &quot;12&quot;, digit);
gsub(/[dD]/, &quot;13&quot;, digit);
gsub(/[eE]/, &quot;14&quot;, digit);
gsub(/[fF]/, &quot;15&quot;, digit);
}
result = result + digit*(16**power);
power++;
}

return (result);

}

vlad
+----------------------------+
| #include<disclaimer.h> |
+----------------------------+

 

[marsd]

The correct way to declare local variables in
a function is with this syntax.

function myfunction(param1, local1,local2,local3) {
 
 if (length(param1) > 20) {
     local1 = substr(param1,1,10)
     local2 = substr(param1,11,20)
     local3 = substr(param1,21,length(param1))
     return local1" "local2" "local3
 }
}

Collisions in the global namespace used by awk
are frustrating but can be avoided by declaring
the variables as local within the function itself.

 

[calabrra]

Vlad/Salem, thanks for your timely and helpful responses.

-Bob