CSAPP shell-lab

shell lab,全部的trace都通过了。代码如下：

 * tsh - A tiny shell program with job control
 * 
 * 
 */
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

/* 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 tr ue, 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)
{
    sigset_t mask,prev,mask_all;
    pid_t pid;
    char *argv[MAXARGS];
    int bg;

    bg = parseline(cmdline,argv);       //首先分析命令行,这样所有的命令行参数都到了argv中

    if(argv[0] == NULL)     //ignore empty line
        return;
    if(!builtin_cmd(argv)){         //不是内置命令，是的话在builtin_cmd就执行了
        sigfillset(&mask_all);
        sigemptyset(&mask);
        sigaddset(&mask,SIGCHLD);
        sigprocmask(SIG_BLOCK,&mask,&prev);     //Block SIGCHLD
        if((pid=fork())==0){                    //child process
            setpgid(0,0);
            sigprocmask(SIG_SETMASK,&prev,NULL);        //unblock SIGCHLD before execve
            if(execve(argv[0],argv,environ)<0){
                printf("%s: Command not found\n",argv[0]);
            }
        }

        sigprocmask(SIG_BLOCK,&mask_all,NULL);      //add之前阻塞所有信号
        //parent process
        if(!bg){
            addjob(jobs,pid,FG,cmdline);
            sigprocmask(SIG_SETMASK,&prev,NULL);        //恢复
            waitfg(pid);
        }
        else{
            addjob(jobs,pid,BG,cmdline);
            struct job_t *job;
            job = getjobpid(jobs,pid);
            printf("[%d] (%d) %s",job->jid,job->pid,job->cmdline);//要在恢复信号之前
            sigprocmask(SIG_SETMASK,&prev,NULL);
        }
    }






    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 直接退出
        exit(0);
    if(strcmp(argv[0],"jobs")==0) {
        listjobs(jobs);
        return 1;
    }
    if(strcmp(argv[0],"bg")==0 || strcmp(argv[0],"fg")==0){
        do_bgfg(argv);
        return 1;
    }
    return 0;     /* not a builtin command */
}

/* 
 * do_bgfg - Execute the builtin bg and fg commands
 */
void do_bgfg(char **argv)
{
    int i = 0,jid = 0,pid = 0;
    struct job_t *job;

    if(argv[1] == NULL){
        printf("%s command requires PID or %%jobid argument\n",argv[0]);
        return;
    }


    /*通过jid或者pid得到job*/
    if(argv[1][0] == '%') {   //是job ID
        while(argv[1][i]!='\0') {
            argv[1][i] = argv[1][i + 1];
            i++;
        }
        jid = atoi(argv[1]);
        if(jid == 0) {
            printf("%s: argument must be a PID or %%jobid\n", argv[0]);
            return;
        }
        job = getjobjid(jobs,jid);
        if(job == NULL){
            printf("%%%d: No such job\n",jid);
            return;
        }
    }
    else {
        pid = atoi(argv[1]);
        if(pid == 0) {
            printf("%s: argument must be a PID or %%jobid\n", argv[0]);
            return;
        }
        job = getjobpid(jobs,pid);
        if(job == NULL){
            printf("(%d): NO such process\n",pid);
            return;
        }
    }

    if(strcmp(argv[0],"bg")==0){
        pid = job->pid;
        kill(-pid,SIGCONT);          //唤醒后台进程,直接继续就可以
        job->state = BG;
        printf("[%d] (%d) %s",job->jid,job->pid,job->cmdline);//

    }
    else{       //fg
        pid = job->pid;
        kill(-pid,SIGCONT);
        job->state = FG;
        waitfg(pid);
    }
}

/* 
 * waitfg - Block until process pid is no longer the foreground process
 */
void waitfg(pid_t pid)
{
    int status;
    sigset_t mask_all,prev_all;

    sigfillset(&mask_all);

    waitpid(pid,&status,WUNTRACED);    //参数应该用这些来完成ctrl-z
    struct job_t *job = getjobpid(jobs,pid);

    if(WIFSIGNALED(status)){        //因一个未被捕获的信号终止
        printf("Job [%d] (%d) terminated by signal %d\n", job->jid, job->pid, WTERMSIG(status));
    }
    if(WIFSTOPPED(status)){         //子进程当前是停止的
        printf("Job [%d] (%d) stopped by signal 20\n",job->jid,job->pid);
        //tsh因为前台进程被停止了,必须让主程序继续走，否则主程序会一直等待前台进程被唤醒
        job->state = ST;//改变前台进程的状态为ST
        return;
    }


    if(!WIFSTOPPED(status)) {
        sigprocmask(SIG_BLOCK, &mask_all, &prev_all);
        deletejob(jobs, pid);        //delete job
        sigprocmask(SIG_SETMASK, &prev_all, NULL);
        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)
{
    sigset_t mask_all,prev_all;

    sigfillset(&mask_all);
    pid_t pid;

    while((pid = waitpid(-1,NULL,WNOHANG))!=0){
        if(pid == -1)
            break;      //出错了
        sigprocmask(SIG_BLOCK,&mask_all,&prev_all);
        deletejob(jobs,pid);
        sigprocmask(SIG_SETMASK,&prev_all,NULL);
    }
    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;

    pid = fgpid(jobs);

    if(pid!=0) {
        kill(-pid, SIGINT);
    }

    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;

    pid = fgpid(jobs);

    if(pid!=0) {
        kill(-pid,SIGTSTP);
    }
    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);
}