pass a value to another c file

Question

I have a A.c file that contains some char* variable str1. I have a B.c file that contains some f() function, that make some transformation on a char* variable.

My point is: How can I pass the value of str to B.c, then compute the new string thanks to f(), and afterwards send back the new string value to A.c ?

How you call the `f()` function? What you mean by 'send back'? Please explain and give more details. A code sample may help. — Bechir, Apr 09 '13 at 16:00
Example: in A.c I have str1 = "hello" I want to make a modification to str1 in B.c (str2 = str1 + "!") After the modification, I want to send back the new value str2 to A.c — TheForbidden, Apr 09 '13 at 16:01
Have a look at [this](http://stackoverflow.com/questions/1045501/how-do-i-share-variables-between-different-c-files) too. — Suvarna Pattayil, Apr 09 '13 at 16:03

score 2 · Answer 1 · answered Apr 09 '13 at 15:56

2

For example:

// file: A.c

char* str1;

and

// file: B.c

extern char* str1;

void f(void)
{
  str1 = "blah";
}

answered Apr 09 '13 at 15:56

Alexey Frunze

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How I get the new value in A.c ? and when I can get it? – TheForbidden Apr 09 '13 at 15:57
`f()` directly modifies `str1`. When it returns, if it has changed the variable, the effect must be observable in `A.c`, `B.c` and everywhere. – Alexey Frunze Apr 09 '13 at 15:58
So I have to call f() in A.c hein? and I will need a header file to compile the files or no ? – TheForbidden Apr 09 '13 at 16:00
1

`char* str1` is a global variable, having a single copy. So any changes made to it are reflected immediately to any function accessing it. – Suvarna Pattayil Apr 09 '13 at 16:01
1

This method makes the variable `str1` shared between the 2 source files. It means that it is the same variable whether it is referred in A.c or in B.c. – ehudt Apr 09 '13 at 16:01
Perhaps you should add some text that advises against the use of global variables – David Heffernan Apr 09 '13 at 16:03

pass a value to another c file

1 Answers1