UNIX for Advanced & Expert Users

calling()
{
fork();

}

main()
{
calling();
printf("IN MAIN\n");
}

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>

#define MAXARGS 20
#define MAXARGLEN 128

int dbg = 0;
int optopt, optind, opterr = 0;
char *optarg;

typedef struct action_ {
    int option; /*reserved*/
    char *progname;
    char *arg[MAXARGS];
} EXEC_ARG;


int do_thread_exec(void *);
void do_vfork_exec(void *);
void do_fork_exec(void *);
void *t_exec(void *);

/*options -a arguments string, -p program name for execution, -t, -v, -f*/
int main(int argc, char **argv)
{
    int opt, n = 0, xid;
    int thread, frk, vfrk;
    char *tmp;
    EXEC_ARG argument;

    if (argc < 3) {
	printf
	    ("Please remember to pass a program name via the -p option and any arguments to the program via -a.\nYou must specify an option from -f,-t,-v to execute anything.\n");
	exit(1);
    }

    thread = frk = vfrk = 0;
    while ((opt = getopt(argc, argv, "a:p:ftvd")) >= 0) {
	switch (opt) {
	case 'p':
	    argument.progname = malloc(strlen(optarg) + 1);
	    strcpy(argument.progname, optarg);
	    break;
	case 'a':

	    if ((tmp = strtok(optarg, " ")) == NULL) {
		argument.arg[n] = NULL;
		break;
	    }
	    argument.arg[n] = malloc(MAXARGLEN);
	    strncpy(argument.arg[n], tmp, MAXARGLEN);
	    n++;
	    while (n < (MAXARGS - 1)) {
		if ((tmp = strtok(NULL, " ")) == NULL) {
		    argument.arg[n] = NULL;
		    break;
		}
		argument.arg[n] = malloc(MAXARGLEN);
		if (dbg > 0) {
		    printf("Copying to %p with string %s at %d.\n",
			   &argument.arg[n], tmp, n);
		}
		strncpy(argument.arg[n], tmp, MAXARGLEN);
		n++;
	    }
	    break;
	case 'v':
	    vfrk = 1;
	    break;
	case 't':
	    thread = 1;
	    break;
	case 'f':
	    frk = 1;
	    break;
	case 'd':
	    dbg = 1;
	    break;
	}
    }

    if (frk > 0) {
	printf("Fork().\n");
	sleep(2);
	do_fork_exec(&argument);
	wait(NULL);
    }
    if (vfrk > 0) {
	printf("Vfork().\n");
	sleep(2);
	do_vfork_exec(&argument);
	wait(NULL);
    }
    if (thread > 0) {
	printf("Threaded...\n");
	sleep(2);
	xid = do_thread_exec(&argument);
	pthread_join(xid, NULL);
    }
    return 0;
}


void *t_exec(void *arg)
{
    EXEC_ARG *ptr = arg;
    execv(ptr->progname, ptr->arg);
    pthread_exit(NULL);
}

int do_thread_exec(void *arg)
{
    pthread_t tid;
    EXEC_ARG *ptr = arg;

    pthread_create(&tid, NULL, t_exec, ptr);
    return tid;
}

void do_vfork_exec(void *arg)
{
    EXEC_ARG *ptr = arg;
    if (vfork() == 0) {
	execv(ptr->progname, ptr->arg);
    }
    return;
}

void do_fork_exec(void *arg)
{
    EXEC_ARG *ptr = arg;
    if (fork() == 0) {
	execv(ptr->progname, ptr->arg);
    }
    return;
}