#tsh.c#

/* 
 * tsh - A tiny shell program with job control
 *
 * You __MUST__ add your user information here below
 * 
 * === User information ===
 * Group: 4
 * User 1: ingibjorgj12
 * SSN: 0301922579
 * User 2: joni12
 * SSN: 2101922989
 * === End User Information ===
 */
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <ctype.h>
#include <signal.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <errno.h>

/* Misc manifest constants */
#define MAXLINE    1024   /* max line size */
#define MAXARGS     128   /* max args on a command line */
#define MAXJOBS      16   /* max jobs at any point in time */
#define MAXJID    1<<16   /* max job ID */

/* Job states */
#define UNDEF 0 /* undefined */
#define FG 1    /* running in foreground */
#define BG 2    /* running in background */
#define ST 3    /* stopped */

/* 
 * Jobs states: FG (foreground), BG (background), ST (stopped)
 * Job state transitions and enabling actions:
 *     FG -> ST  : ctrl-z
 *     ST -> FG  : fg command
 *     ST -> BG  : bg command
 *     BG -> FG  : fg command
 * At most 1 job can be in the FG state.
 */

/* Global variables */
extern char **environ;      /* defined in libc */
char prompt[] = "tsh> ";    /* command line prompt (DO NOT CHANGE) */
int verbose = 0;            /* if true, print additional output */
int nextjid = 1;            /* next job ID to allocate */
char sbuf[MAXLINE];         /* for composing sprintf messages */

struct job_t {              /* The job struct */
    pid_t pid;              /* job PID */
    int jid;                /* job ID [1, 2, ...] */
    int state;              /* UNDEF, BG, FG, or ST */
    char cmdline[MAXLINE];  /* command line */
};
struct job_t jobs[MAXJOBS]; /* The job list */
/* End global variables */


/* Function prototypes */

/* Here are the functions that you will implement */
void eval(char *cmdline);
int builtin_cmd(char **argv);
void do_bgfg(char **argv);
void waitfg(pid_t pid);

void sigchld_handler(int sig);
void sigtstp_handler(int sig);
void sigint_handler(int sig);

/* Here are helper routines that we've provided for you */
int parseline(const char *cmdline, char **argv); 
void sigquit_handler(int sig);

void clearjob(struct job_t *job);
void initjobs(struct job_t *jobs);
int maxjid(struct job_t *jobs); 
int addjob(struct job_t *jobs, pid_t pid, int state, char *cmdline);
int deletejob(struct job_t *jobs, pid_t pid); 
pid_t fgpid(struct job_t *jobs);
struct job_t *getjobpid(struct job_t *jobs, pid_t pid);
struct job_t *getjobjid(struct job_t *jobs, int jid); 
int pid2jid(pid_t pid); 
void listjobs(struct job_t *jobs);

void usage(void);
void unix_error(char *msg);
void app_error(char *msg);
typedef void handler_t(int);
handler_t *Signal(int signum, handler_t *handler);

/*
 * main - The shell's main routine 
 */
int main(int argc, char **argv) 
{
    char c;
    char cmdline[MAXLINE];
    int emit_prompt = 1; /* emit prompt (default) */

    /* Redirect stderr to stdout (so that driver will get all output
     * on the pipe connected to stdout) */
    dup2(1, 2);

    /* Parse the command line */
    while ((c = getopt(argc, argv, "hvp")) != EOF) {
        switch (c) {
        case 'h':             /* print help message */
            usage();
	    break;
        case 'v':             /* emit additional diagnostic info */
            verbose = 1;
	    break;
        case 'p':             /* don't print a prompt */
            emit_prompt = 0;  /* handy for automatic testing */
	    break;
	default:
            usage();
	}
    }

    /* Install the signal handlers */

    /* These are the ones you will need to implement */
    Signal(SIGINT,  sigint_handler);   /* ctrl-c */
    Signal(SIGTSTP, sigtstp_handler);  /* ctrl-z */
    Signal(SIGCHLD, sigchld_handler);  /* Terminated or stopped child */

    /* This one provides a clean way to kill the shell */
    Signal(SIGQUIT, sigquit_handler); 

    /* Initialize the job list */
    initjobs(jobs);

    /* Execute the shell's read/eval loop */
    while (1) {

	/* Read command line */
	if (emit_prompt) {
	    printf("%s", prompt);
	    fflush(stdout);
	}
	if ((fgets(cmdline, MAXLINE, stdin) == NULL) && ferror(stdin)) {
	    app_error("fgets error");
	}
	if (feof(stdin)) { /* End of file (ctrl-d) */
	    fflush(stdout);
	    exit(0);
	}

	/* Evaluate the command line */
	eval(cmdline);
	fflush(stdout);
	fflush(stdout);
    } 

    exit(0); /* control never reaches here */
}
  
/* 
 * eval - Evaluate the command line that the user has just typed in
 * 
 * If the user has requested a built-in command (quit, jobs, bg or fg)
 * then execute it immediately. Otherwise, fork a child process and
 * run the job in the context of the child. If the job is running in
 * the foreground, wait for it to terminate and then return.  Note:
 * each child process must have a unique process group ID so that our
 * background children don't receive SIGINT (SIGTSTP) from the kernel
 * when we type ctrl-c (ctrl-z) at the keyboard.  
 */
void eval(char *cmdline) 
{
	pid_t pid; 				/* Process is*/
	struct job_t *job;			/* Pointer to job */
	char *argv[MAXARGS]; 			/* Creating argument vector */
	int bg = parseline(cmdline, argv); 	/* Parses input */
	int bicmd = builtin_cmd(argv); 		/* Execute cmd if built in */
	sigset_t mask;          		/* Mask to block signals */

	if (!bicmd){
		sigemptyset(&mask);			/* Init an empty mask */
		sigaddset(&mask, SIGCHLD);		/* Adding SIGCHLD to mask*/
		sigprocmask(SIG_BLOCK, &mask, 0);	/* Block signals with mask */
		
		if ((pid = fork()) == 0) {				/* In child */
			sigprocmask(SIG_UNBLOCK, &mask, NULL);  	/* Unblock signals */
			setpgid(0,0);					/* New child process group id */
			execvp(argv[0], argv);				/* Execute command with argument vector */
			printf("%s: Command not found\n", argv[0]);
			fflush(stdout);
			exit(1);
		}
		if (!bg) {						/* Forground process */
			addjob(jobs, pid, FG, cmdline);			/* Add job to job list */
			sigprocmask(SIG_UNBLOCK, &mask, NULL);		/* Unblock signals */ 
			waitfg(pid);	
		}
		else {									/* Background process */
			addjob(jobs, pid, BG, cmdline);					/* Add job to job list */
			job = getjobpid(jobs, pid);					/* Get job for jid */
			printf("[%d] (%d) %s", job->jid, job->pid, job->cmdline );	
			fflush(stdout);
			sigprocmask(SIG_UNBLOCK, &mask, NULL);				/* Unblock signals */
		}
	}	
    return;
}

/* 
 * parseline - Parse the command line and build the argv array.
 * 
 * Characters enclosed in single quotes are treated as a single
 * argument.  Return true if the user has requested a BG job, false if
 * the user has requested a FG job.  
 */
int parseline(const char *cmdline, char **argv) 
{
    static char array[MAXLINE];	/* holds local copy of command line */
    char *buf = array;			/* ptr that traverses command line */
    char *delim;				/* points to first space delimiter */
    int argc;					/* number of args */
    int bg;						/* background job? */

    strcpy(buf, cmdline);
    buf[strlen(buf)-1] = ' ';	/* replace trailing '\n' with space */
    while (*buf && (*buf == ' ')) { /* ignore leading spaces */
	buf++;
    }

    /* Build the argv list */
    argc = 0;
    if (*buf == '\'') {
	buf++;
	delim = strchr(buf, '\'');
    }
    else {
	delim = strchr(buf, ' ');
    }

    while (delim) {
	argv[argc++] = buf;
	*delim = '\0';
	buf = delim + 1;
	while (*buf && (*buf == ' ')) { /* ignore spaces */
	    buf++;
	}

	if (*buf == '\'') {
	    buf++;
	    delim = strchr(buf, '\'');
	}
	else {
	    delim = strchr(buf, ' ');
	}
    }
    argv[argc] = NULL;
    
    if (argc == 0) { /* ignore blank line */
	return 1;
    }

    /* should the job run in the background? */
    if ((bg = (*argv[argc-1] == '&')) != 0) {
	argv[--argc] = NULL;
    }
    return bg;
}

/* 
 * builtin_cmd - If the user has typed a built-in command then execute
 *    it immediately.  
 */
int builtin_cmd(char **argv) 
{
	if (strcmp(argv[0], "quit") == 0) {		/* Quit command */
		exit(0);
	}
	if (strcmp(argv[0], "fg") == 0) {		/* Forground command */
		do_bgfg(argv);
		return 1;
	}
	if (strcmp(argv[0], "bg") == 0) {		/* Background command */
		do_bgfg(argv);
		return 1;
	}
	if (strcmp(argv[0], "jobs") == 0) {		/* Jobs command */
		listjobs(jobs);						/* Lists all jobs */
		return 1;
	}
    return 0;     							/* Not a builtin command */
}

/* 
 * do_bgfg - Execute the builtin bg and fg commands
 */
void do_bgfg(char **argv) 
{
	if (argv[1] != NULL ) {							/* Check for pid or jid */
		struct job_t *job;
		if (strstr(argv[1], "%") != NULL){ 			/* Check if jid */
			char* argvchar = argv[1]; 
			if (!isdigit(argvchar[1])) {			/* Check if invalid argv */
				printf("%s command requires PID or %%jobid\n", argv[0]);
				fflush(stdout);
				return;	
			}
			int jid = atoi(argv[1]+1);	 			/* Extract jid */
			job = getjobjid(jobs, jid);				/* Get job from jid */
			if (!job) {								/* Job not found */
				printf("%s: No such job\n", argv[1]);
				fflush(stdout);
				return;
			}
		}
		else {										/* Else pid */
			char* argvchar = argv[1];
			if (!isdigit(argvchar[0])) {			/* Check if invalid argv */
				printf("%s command requires PID or %%jobid\n", argv[0]);
				fflush(stdout);
				return;
			}
			int pid = atoi(argv[1]);				/* Extract pid */
			job = getjobpid(jobs, pid);				/* Get job from jid */
			if (job == NULL) {						/* Job not found */
				printf("(%s): No such process\n", argv[1]);	
				fflush(stdout);
				return;
			}	
		}
		if (strcmp(argv[0], "bg") == 0) {			/* To background */
			printf("[%d] (%d) %s", job->jid, job->pid, job->cmdline);
			fflush(stdout);
			job->state = BG;						/* Changing status to BG */
			kill(-job->pid, SIGCONT);				/* Sending SIGCONT to pid*/
		}
		else{										/* To forground */
			job->state = FG;						/* Changing status to FG */
			kill(-job->pid, SIGCONT);				/* Sending SIGCONT to pid*/	
			waitfg(job->pid);
		}
	}
	else {											/* Missing argument */
		printf("%s command requires PID or %%jobid argument\n", argv[0]);
		fflush(stdout);
	}
	return;
}

/* 
 * waitfg - Block until process pid is no longer the foreground process
 */
void waitfg(pid_t pid)
{	
	while (fgpid(jobs) == pid) {	/* While pid is in forground */
		sleep(1);					/* Sleep */
	}
	return;
}

/*****************
 * Signal handlers
 *****************/

/* 
 * sigchld_handler - The kernel sends a SIGCHLD to the shell whenever
 *     a child job terminates (becomes a zombie), or stops because it
 *     received a SIGSTOP or SIGTSTP signal. The handler reaps all
 *     available zombie children, but doesn't wait for any other
 *     currently running children to terminate.  
 */
void sigchld_handler(int sig) 
{
	pid_t pid;							/* Child process id */
	int status;							/* Job status */
	struct job_t *job;					/* Job pointer */
	
	while ((pid = waitpid(-1, &status, WNOHANG | WUNTRACED)) > 0){ /* Handeling child process */
		if (WIFEXITED(status)) {		/* Child terminates normally */
			deletejob(jobs, pid);		/* Delete job from job list */
		}
		else if (WIFSTOPPED(status)) {	/* Child process is stopped */
			job = getjobpid(jobs, pid);	/* Get job with pid */
			printf("Job [%d] (%d) stopped by signal %d\n", job->jid, job->pid, 20);
			fflush(stdout);
			job->state = ST;			/* Change job state to stopped */
		}
		else if (WIFSIGNALED(status)) { /* Uncaught signal to terminate child*/
			job = getjobpid(jobs, pid);	/* Get job with pid */
			printf("Job [%d] (%d) terminated by signal %d\n", job->jid, job->pid, 2);
			fflush(stdout);
			deletejob(jobs, pid);		/* Delete job from job list */
		}
	}
   	return;
}

/* 
 * sigint_handler - The kernel sends a SIGINT to the shell whenver the
 *    user types ctrl-c at the keyboard.  Catch it and send it along
 *    to the foreground job.  
 */
void sigint_handler(int sig) 
{
	pid_t pid = fgpid(jobs);	/* Get pid of forground process */
	if (pid != 0) {				/* Check if process is found */
		kill(-pid, SIGINT);		/* Send SIGINT to process group */
	} 
	return;
}

/*
 * sigtstp_handler - The kernel sends a SIGTSTP to the shell whenever
 *     the user types ctrl-z at the keyboard. Catch it and suspend the
 *     foreground job by sending it a SIGTSTP.  
 */
void sigtstp_handler(int sig) 
{
	pid_t pid = fgpid(jobs);	/* Get pid of forground process */
	if (pid != 0) {				/* Check if process is found */
		kill(-pid, SIGTSTP); 	/* Send SIGTSTP to process group */
	}
	return;
}

/*********************
 * End signal handlers
 *********************/

/***********************************************
 * Helper routines that manipulate the job list
 **********************************************/

/* clearjob - Clear the entries in a job struct */
void clearjob(struct job_t *job) {
    job->pid = 0;
    job->jid = 0;
    job->state = UNDEF;
    job->cmdline[0] = '\0';
}

/* initjobs - Initialize the job list */
void initjobs(struct job_t *jobs) {
    int i;

    for (i = 0; i < MAXJOBS; i++)
	clearjob(&jobs[i]);
}

/* maxjid - Returns largest allocated job ID */
int maxjid(struct job_t *jobs) 
{
    int i, max=0;

    for (i = 0; i < MAXJOBS; i++) {
	if (jobs[i].jid > max) {
	    max = jobs[i].jid;
	}
    }
    return max;
}

/* addjob - Add a job to the job list */
int addjob(struct job_t *jobs, pid_t pid, int state, char *cmdline) 
{
    int i;
    
    if (pid < 1) {
	return 0;
    }

    for (i = 0; i < MAXJOBS; i++) {
	if (jobs[i].pid == 0) {
	    jobs[i].pid = pid;
	    jobs[i].state = state;
	    jobs[i].jid = nextjid++;
	    if (nextjid > MAXJOBS) {
		nextjid = 1;
	    }
	    strcpy(jobs[i].cmdline, cmdline);
	    if (verbose){
		printf("Added job [%d] %d %s\n", jobs[i].jid, jobs[i].pid, jobs[i].cmdline);
            }
            return 1;
	}
    }
    printf("Tried to create too many jobs\n");
    return 0;
}

/* deletejob - Delete a job whose PID=pid from the job list */
int deletejob(struct job_t *jobs, pid_t pid) 
{
    int i;

    if (pid < 1) {
	return 0;
    }

    for (i = 0; i < MAXJOBS; i++) {
	if (jobs[i].pid == pid) {
	    clearjob(&jobs[i]);
	    nextjid = maxjid(jobs)+1;
	    return 1;
	}
    }
    return 0;
}

/* fgpid - Return PID of current foreground job, 0 if no such job */
pid_t fgpid(struct job_t *jobs) {
    int i;

    for (i = 0; i < MAXJOBS; i++) {
	if (jobs[i].state == FG) {
	    return jobs[i].pid;
	}
    }
    return 0;
}

/* getjobpid  - Find a job (by PID) on the job list */
struct job_t *getjobpid(struct job_t *jobs, pid_t pid) {
    int i;

    if (pid < 1) {
	return NULL;
    }
    for (i = 0; i < MAXJOBS; i++) {
	if (jobs[i].pid == pid) {
	    return &jobs[i];
	}
    }
    return NULL;
}

/* getjobjid  - Find a job (by JID) on the job list */
struct job_t *getjobjid(struct job_t *jobs, int jid) 
{
    int i;

    if (jid < 1) {
	return NULL;
    }
    for (i = 0; i < MAXJOBS; i++) {
	if (jobs[i].jid == jid) {
	    return &jobs[i];
	}
    }
    return NULL;
}

/* pid2jid - Map process ID to job ID */
int pid2jid(pid_t pid) 
{
    int i;

    if (pid < 1) {
	return 0;
    }
    for (i = 0; i < MAXJOBS; i++) {
	if (jobs[i].pid == pid) {
            return jobs[i].jid;
        }
    }
    return 0;
}

/* listjobs - Print the job list */
void listjobs(struct job_t *jobs) 
{
    int i;
    
    for (i = 0; i < MAXJOBS; i++) {
	if (jobs[i].pid != 0) {
	    printf("[%d] (%d) ", jobs[i].jid, jobs[i].pid);
	    switch (jobs[i].state) {
	    case BG: 
		printf("Running ");
		break;
	    case FG: 
		printf("Foreground ");
		break;
	    case ST: 
		printf("Stopped ");
		break;
	    default:
		printf("listjobs: Internal error: job[%d].state=%d ", 
		       i, jobs[i].state);
	    }
	    printf("%s", jobs[i].cmdline);
	}
    }
}
/******************************
 * end job list helper routines
 ******************************/


/***********************
 * Other helper routines
 ***********************/

/*
 * usage - print a help message
 */
void usage(void) 
{
    printf("Usage: shell [-hvp]\n");
    printf("   -h   print this message\n");
    printf("   -v   print additional diagnostic information\n");
    printf("   -p   do not emit a command prompt\n");
    exit(1);
}

/*
 * unix_error - unix-style error routine
 */
void unix_error(char *msg)
{
    fprintf(stdout, "%s: %s\n", msg, strerror(errno));
    exit(1);
}

/*
 * app_error - application-style error routine
 */
void app_error(char *msg)
{
    fprintf(stdout, "%s\n", msg);
    exit(1);
}

/*
 * Signal - wrapper for the sigaction function
 */
handler_t *Signal(int signum, handler_t *handler) 
{
    struct sigaction action, old_action;

    action.sa_handler = handler;  
    sigemptyset(&action.sa_mask); /* block sigs of type being handled */
    action.sa_flags = SA_RESTART; /* restart syscalls if possible */

    if (sigaction(signum, &action, &old_action) < 0) {
	unix_error("Signal error");
    }
    return (old_action.sa_handler);
}

/*
 * sigquit_handler - The driver program can gracefully terminate the
 *    child shell by sending it a SIGQUIT signal.
 */
void sigquit_handler(int sig) 
{
    printf("Terminating after receipt of SIGQUIT signal\n");
    exit(1);
}