A simple C code snippet that shows how to do a function call.

Posted: May 15, 2015. At: 10:43 AM. This was 3 years ago. Post ID: 8200
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Do a simple function call in C. This code snippet shows how to do this

This simple C code snippet shows how to do a function call in C. This calls the hi() function and runs it in main(). Very simple but useful code. And this does not need to call any include files. As I am using the built-in write() function.

int hi()
{
        int i;
        i = 0;
 
        write(1, "Hi.\n", 5);
 
        while (i < 8) {
                system("echo 'This is a loop.'");
                i++;
        }
}
 
int main(int argc, char** argv)
{
        write(1, "Hello World\n", 15);
        hi();
 
        return 0;
}

A nice function that reads a file and performs various operations on it, depending on the contents.

void kernel(const char *File, int len)
{
	FILE *f;
	char Kyo[40];
 
	if (len > 10 or len < 2)
		return;
 
	f = fopen(File, "r");
	if(!f) {
		printf ("Sorry, I cannot open: %s.\n", File);
		printf("Please check your permissions with\n"		\
			"your supervisor. The feature may not\n"	\
			"be compiled and\\or enabled in your\n"		\
			"kernel version. Or a scsi device, eg,\n"	\
			"a USB drive may not be attached.\n");
		return;
	} else {
/* Based on sample code from:
 * www.koders.com/c/fid84CFEFBF311605F963CB04E0F84A2F52A8120F33.aspx
 * Specifically the section on parsing the /proc/version.
 */
		while (feof(f) != 1) {
			fgets(Kyo, len, f);
			if (strncmp(Kyo, "((", 1) == 0)
				printf ("\n-");
			if (strncmp(Kyo, "#", 1) == 0) {
				printf ("\nVersion: #");
			} else {
/*
 * This function is fast, owing to this i feel. especially with gcc 
 * 4.3.2 & glibc 2.5+. it is faster than using: printf (Kyo);
 */
				fprintf (stdout, "%s", Kyo);
			}
			fflush(stdout);
		}
	}
	fclose(f);
}

Feeding the version number and other text into a text block to create a very nice banner for my program to print out.

enum { VERSION = 150 };
#define SYSINFO "Sysinfo version v%i.%i"
 
const char *p = "System Information Program";
char ver[128];
 
void print_menu()
{
	printf("\tSysinfo. %s\n\n", p);
 
	printf("1 - Kernel Information.\n2 - Memory & processes.\n");
	printf("3 - CDROM Information.\n4 - View list of sound cards.\n");
	printf("5 - View Real Time Clock Information.\n");
	printf("6 - View motherboard and BIOS information.\n");
/*	printf("7 - View information about your hard drive.\n"); */
 
	sprintf (ver, SYSINFO, VERSION / 100, VERSION % 100);
 
	printf("\n%s, by John Cartwright 2007.\nsysinfo comes with ", ver);
	printf("ABSOLUTELY NO WARRANTY. This\n is open source software,");
	printf("and you are welcome to \nredistribute it under certain ");
	printf("conditions as \noutlined in the GNU Public License.\n\n");
	exit(0);
}

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