Question

I have written a C program. It compiles and works fine on DevC on Windows 7.
But when I compile it on Linux mint (using ‘gcc main.c’ command) it does not compile and give errors. These errors are not shown while compiling on Windows 7. So nothing must be wrong on Linux as well! How to compile it on Linux through gcc?

C Code:

#include <stdio.h>
#include <stdlib.h>

int main(int argc, char *argv[])
{
   char command[100];

   printf("Enter the command:");
   scanf("%[^\t\n]", &command);
   printf("%s\n", command);
   strchr(command, '&');

   printf("%i", strchr(command, '&'));

   system("PAUSE"); 

   return 0;
}

Errors:

mint@mint ~ $ gcc ass1/main.c
ass1/main.c: In function 'main':
ass1/main.c:8:5: warning: format '%[^   
' expects argument of type 'char *', but argument 2 has type 'char (*)[100]' [-Wformat]
ass1/main.c:11:3: warning: incompatible implicit declaration of built-in function 'strchr' [enabled by default]
ass1/main.c:13:5: warning: format '%i' expects argument of type 'int', but argument 2 has type 'char *' [-Wformat]

Answer 1

Those aren’t errors, they’re warnings. Your code should have still compiled.

The first warnings is because you’re passing &command to scanf, which is of type char (*)[100], and the specifier %s expects an argument of type char *. All you simply need to do is pass command to scanf (without the &), since a char array will decay into a char* when passed to a function.

You’ll probably find that the code still works, with command and &command both referring to the same address (printf("%p %p", command, &command);).

The second warning is due to you forgetting to include <string.h>, which declares strchr. Since the compiler can’t find the declaration, it implicitly generates one, which doesn’t turn out to match the real one.

Lastly, strchr returns a char*, and the specifier %i is intended to be used for ints. If you want to print out an address using printf, use the %p specifier.

You should also probably avoid system("PAUSE"); (which won’t work on Linux), and replace it with a function that waits for user input.