How do i open a new terminal window using fork()? - c

Question

In my program I call the function fork() and then I want the child process that fork creates to open a new terminal window.
This is the code I have right now:
/*
* Shows user info from local pwfile.
*
* Usage: userinfo username
*/
#define _XOPEN_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "pwdblib.h" /* include header declarations for pwdblib.c */
#include <pwd.h>
#include <unistd.h>
#define _XOPEN_SOURCE /* See feature_test_macros(7) */
#include <unistd.h>
/* Define some constants. */
#define USERNAME_SIZE (32)
#define NOUSER (-1)
int print_info(const char *username)
{
struct pwdb_passwd *p = pwdb_getpwnam(username);
if (p != NULL) {
printf("Name: %s\n", p->pw_name);
printf("Passwd: %s\n", p->pw_passwd);
printf("Uid: %u\n", p->pw_uid);
printf("Gid: %u\n", p->pw_gid);
printf("Real name: %s\n", p->pw_gecos);
printf("Home dir: %s\n",p->pw_dir);
printf("Shell: %s\n", p->pw_shell);
return 0;
} else {
return NOUSER;
}
}
int user_authentication(const char *username , const char *password){
struct pwdb_passwd *pw_entry;
char *salt = malloc(2); // Allocate 2 bytes of memory for the salt variable
int pwdcmp; // return value after comparison
char *pwdcrypt; //the hashed password
pw_entry = pwdb_getpwnam(username); // get struct line for username in pwfile
if(pw_entry != NULL){ //If the structure exist
memcpy(salt, pw_entry->pw_passwd, 2); // Take the 2 first bits of password will be in salt
pwdcrypt = crypt(password, salt); // Hashed value
pwdcmp = strcmp(pwdcrypt , pw_entry->pw_passwd); // Compare the passwords
if(pwdcmp == 0){ // if passwords are correct return 1
return 1;
} else{
return -1; // passwords are incorrect
}
}
}
void read_username(char *username)
{
printf("login: ");
fgets(username, USERNAME_SIZE, stdin);
/* remove the newline included by getline() */
username[strlen(username) - 1] = '\0';
}
int main(int argc, char **argv)
{
char username[USERNAME_SIZE];
char *inputpwd;
int login = 0;
int pwd_failed; // Failed login counter
int pwd_age; // age of password counter
struct pwdb_passwd *pw_entry;
/*/ Until successful login, run this loop */
while(login == 0){
signal(2, SIG_IGN);
/*
* Write "login: " and read user input. Copies the username to the
* username variable.
*/
read_username(username);
/* Displays a propt to password, reads in the password */
inputpwd = getpass("Password: ");
/*/ Gets the structure of specifik username */
pw_entry = pwdb_getpwnam(username);
/*/ Return the age & failed passwords counter*/
pwd_age = pw_entry->pw_age;
pwd_failed = pw_entry->pw_failed;
/* Check authentication, successful terminates program by login = 1 else
* run the program again
*/
if(user_authentication(username , inputpwd) == 1 && pwd_failed > -1){
printf("User authenticated successfully\n");
if(pwd_age > 2){
printf("Time to change password\n");
}
pwd_failed = 0; // successful login resets failed atempts
pwd_age++;
pw_entry->pw_age = pwd_age; //Update age in file
pwdb_update_user(pw_entry);
login = 1;
pid_t pid;
int status;
pid = fork();
if (pid==0) {
/* This is the child process. Run an xterm window */
execl("/usr/bin/xterm", "xterm", "-e", "yourprogram", NULL);
/* if child returns we must inform parent.
* Always exit a child process with _exit() and not return() or exit().
*/
_exit(-1);
} else if (pid < 0) { /* Fork failed */
printf("Fork faild\n");
status = -1;
} else {
/* This is parent process. Wait for child to complete */
if (waitpid(pid, &status, 0) != pid) {
status = -1;
}
}
}
else if(user_authentication(username, inputpwd) == -1){
pwd_failed++; //increase counter by 1 of failedlogins
pw_entry->pw_failed = pwd_failed; //update failed counter in file
if(pwd_failed > 1){
pwd_failed = -1;
}
printf("\nWrong password: %s\n", username);
pwdb_update_user(pw_entry);
return 0;
}
else{
printf("Unknown user or incorrect password\n");
return 0;
}
//pw_entry->pw_age = pwd_age; //Update age in file
//pw_entry->pw_failed = pwd_failed; //update failed counter in file
pwdb_update_user(pw_entry); //Update actual file
/* Show user info from our local pwfile. */
if (print_info(username) == NOUSER) {
/* if there are no user with that usename... */
printf("\nFound no user with name: %s\n", username);
return 0;
}}}
What I want to happen is for the new terminal window to run a function, which I've implemented myself. I'm not very sure on how to go about this, anyone got some ideas or directions to help?
EDIT:
I have edited the question now so that the entire program is visible. Below is what the program should be able to do. I have no idea how to go any further...
After a successful authentication of a user, your program should fork and start a terminal
window with the user’s preferred shell. The parent process should just wait until the child
exits and then show the "login:" prompt again.
Before starting the terminal window, the child process should set the right real and effective
user of the process, and the right real and effective group.

Answer 1

execl("/usr/bin/xterm", "xterm", "-e", "yourprogram", NULL);