Implementing an exit function on my C shell - c

Question

I have been trying to implement an exit command on my C shell. I have tried the fork-exec method since it's a system call.
When I run the program, it prompts for the stdin input and when I type in "exit" it returns a "segmentation fault (core dumped)" error.
What am I doing wrong?
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/wait.h>
#include <fcntl.h>
#define ARGVMAX 100
#define LINESIZE 1024
#define EXITCMD "exit"
//makeargv - builds an argv vector from words in a string
int makeargv(char *s, char *argv[ARGVMAX]) {
int ntokens = 0;
if (s == NULL || argv == NULL || ARGVMAX == 0)
return -1;
argv[ntokens] = strtok(s, " \t\n");
while ((argv[ntokens] != NULL) && (ntokens < ARGVMAX)) {
ntokens++;
argv[ntokens] = strtok(NULL, " \t\n");
}
argv[ntokens] = NULL; // it must terminate with NULL
return ntokens;
}
void prompt() {
printf("sish> ");
fflush(stdout); //writes the prompt
}
/****** MAIN ******/
int main() {
char line[LINESIZE];
int wstatus;
while (1) {
prompt();
if (fgets(line, LINESIZE, stdin) == NULL)
break;
// TODO:
if(fgets(line, LINESIZE, strcmp(stdin, EXITCMD )) == 0)
return 0;
signal(SIGINT, SIG_DFL);
if (fork() == 0) exit(execvp(line[0], line));
{
signal(SIGINT, SIG_IGN);
}
wait(&wstatus);
if(WIFEXITED(wstatus))
printf("<%d>", WEXITSTATUS(wstatus));
}
return 0;
}

Answer 1

After reviewing and cleaning the code, I was finally able to implement the exit command.
Here goes the code:
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/wait.h>
#include <fcntl.h>
#define ARGVMAX 100
#define LINESIZE 1024
#define EXITCMD "exit"
//makeargv - build an argv vector from words in a string
int makeargv(char *s, char *argv[ARGVMAX]) {
int ntokens = 0;
if (s == NULL || argv == NULL || ARGVMAX == 0)
return -1;
argv[ntokens] = strtok(s, " \t\n");
while ((argv[ntokens] != NULL) && (ntokens < ARGVMAX)) {
ntokens++;
argv[ntokens] = strtok(NULL, " \t\n");
}
argv[ntokens] = NULL; // it must terminate with NULL
return ntokens;
}
void prompt() {
printf("C Shell >> ");
fflush(stdout); //writes the prompt
}
/****** MAIN ******/
int main() {
char line[LINESIZE];
while (1) {
prompt();
if (fgets(line, LINESIZE, stdin) == NULL)
break;
// TODO:
char *p = strchr(line, '\n');
if (p)
*p = 0;
if(strcmp(line, "exit") == 0)
break;
char *args[] = {line, (char*) 0};
int pid = fork();
if (pid == 0){
execvp(line, args);
perror("Command Error!");
exit(1);
} else {
wait(NULL);
}
return 0;
}
return 0;
}