How to build multi file program using gcc???

So i have 3 files. main.c, test.c and test.h

main.c contains:

Code:

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#include "test.h"
#include <stdio.h>
and code

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test.c

Code:

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#include "test.h"
and code

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test.h

Code:

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typedef struct {
int test1;
int test2;
int test3;
} test;

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How would i build this???

i tried gcc -o main.c test.c test.h
but i get a compiler error

gcc -o prog main.c test.c

Quote:

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Originally Posted by Salem

gcc -o prog main.c test.c

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i did that and i get:

Code:

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test.c: In function ‘input_test’:
test.c:21: warning: incompatible implicit declaration of built-in function ‘scanf’
test.c:21: error: ‘test1’ undeclared (first use in this function)
test.c:21: error: (Each undeclared identifier is reported only once
test.c:21: error: for each function it appears in.)
test.c:21: error: ‘test2’undeclared (first use in this function)
test.c:21: error: ‘test3’ undeclared (first use in this function)
test.c:22: warning: ‘return’ with a value, in function returning void

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Code:

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test.c:21: warning: incompatible implicit declaration of built-in function ‘scanf’

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on main.c there is #include <stdio.h>, so why would i get this error??

Because those errors are in test.c. If you plan on using functions from stdio.h in test.c, then you must #include it in test.c.

As a side note, it would be good to get in the habit of turning the warnings all the way up, and make sure you fix them all. Just add a -Wall to the commandline:
gcc -Wall -o prog main.c test.c

how about

Code:

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test.c:21: error: ‘test1’ undeclared (first use in thisfunction)

test.c:21: error: (Each undeclared identifier is reported only once

test.c:21: error: foreach function it appears in.)
test.c:21: error: ‘test2’undeclared (first use in thisfunction)
test.c:21: error: ‘test3’ undeclared (first use in thisfunction)

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they are defined in test.h

Code:

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typedef struct {
int test1;
int test2;
int test3;
} test;

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Well, I can't say for sure, since you didn't actually post any code for test.c. I'm guessing you're not using them as members of a struct. They do not work as variables on their own when declared inside a struct like you did.

Quote:

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Originally Posted by anduril462

Well, I can't say for sure, since you didn't actually post any code for test.c. I'm guessing you're not using them as members of a struct. They do not work as variables on their own when declared inside a struct like you did.

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weird that error just went away.. the code is

Code:

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void input_test(test *dp)
{
scanf("%d", &test.test1);
return;
}

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That should not actually work. test is the name of a type, not a variable. You can't reference a member (e.g. test1) of the type itself. You must reference the test1 member of a variable. Something here doesn't add up. You're not showing the full code (the entire contents of every file) exactly as it is on your system, or you've changed something.