604 lines
15 KiB
C
604 lines
15 KiB
C
/*
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* tsh - A tiny shell program with job control
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*
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* <Put your name and login ID here>
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <string.h>
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#include <ctype.h>
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#include <signal.h>
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#include <sys/types.h>
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#include <sys/wait.h>
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#include <errno.h>
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/* Misc manifest constants */
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#define MAXLINE 1024 /* max line size */
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#define MAXARGS 128 /* max args on a command line */
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#define MAXJOBS 16 /* max jobs at any point in time */
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#define MAXJID 1<<16 /* max job ID */
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/* Job states */
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#define UNDEF 0 /* undefined */
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#define FG 1 /* running in foreground */
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#define BG 2 /* running in background */
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#define ST 3 /* stopped */
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/*
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* Jobs states: FG (foreground), BG (background), ST (stopped)
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* Job state transitions and enabling actions:
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* FG -> ST : ctrl-z
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* ST -> FG : fg command
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* ST -> BG : bg command
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* BG -> FG : fg command
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* At most 1 job can be in the FG state.
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*/
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/* Global variables */
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extern char **environ; /* defined in libc */
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char prompt[] = "tsh> "; /* command line prompt (DO NOT CHANGE) */
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int verbose = 0; /* if true, print additional output */
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int nextjid = 1; /* next job ID to allocate */
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char sbuf[MAXLINE]; /* for composing sprintf messages */
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struct job_t { /* The job struct */
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pid_t pid; /* job PID */
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int jid; /* job ID [1, 2, ...] */
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int state; /* UNDEF, BG, FG, or ST */
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char cmdline[MAXLINE]; /* command line */
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};
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struct job_t jobs[MAXJOBS]; /* The job list */
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/* End global variables */
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/* Function prototypes */
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/* Here are the functions that you will implement */
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void eval(char *cmdline);
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int builtin_cmd(char **argv);
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void do_bgfg(char **argv);
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void waitfg(pid_t pid);
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void sigchld_handler(int sig);
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void sigtstp_handler(int sig);
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void sigint_handler(int sig);
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/* Here are helper routines that we've provided for you */
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int parseline(const char *cmdline, char **argv);
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void sigquit_handler(int sig);
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void clearjob(struct job_t *job);
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void initjobs(struct job_t *jobs);
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int maxjid(struct job_t *jobs);
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int addjob(struct job_t *jobs, pid_t pid, int state, char *cmdline);
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int deletejob(struct job_t *jobs, pid_t pid);
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pid_t fgpid(struct job_t *jobs);
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struct job_t *getjobpid(struct job_t *jobs, pid_t pid);
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struct job_t *getjobjid(struct job_t *jobs, int jid);
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int pid2jid(pid_t pid);
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void listjobs(struct job_t *jobs);
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void usage(void);
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void unix_error(char *msg);
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void app_error(char *msg);
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typedef void handler_t(int);
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handler_t *Signal(int signum, handler_t *handler);
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/*
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* main - The shell's main routine
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*/
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int main(int argc, char **argv)
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{
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char c;
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char cmdline[MAXLINE];
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int emit_prompt = 1; /* emit prompt (default) */
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/* Redirect stderr to stdout (so that driver will get all output
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* on the pipe connected to stdout) */
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dup2(1, 2);
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/* Parse the command line */
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while ((c = getopt(argc, argv, "hvp")) != EOF) {
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switch (c) {
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case 'h': /* print help message */
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usage();
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break;
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case 'v': /* emit additional diagnostic info */
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verbose = 1;
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break;
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case 'p': /* don't print a prompt */
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emit_prompt = 0; /* handy for automatic testing */
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break;
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default:
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usage();
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}
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}
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/* Install the signal handlers */
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/* These are the ones you will need to implement */
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Signal(SIGINT, sigint_handler); /* ctrl-c */
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Signal(SIGTSTP, sigtstp_handler); /* ctrl-z */
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Signal(SIGCHLD, sigchld_handler); /* Terminated or stopped child */
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/* This one provides a clean way to kill the shell */
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Signal(SIGQUIT, sigquit_handler);
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/* Initialize the job list */
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initjobs(jobs);
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/* Execute the shell's read/eval loop */
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while (1) {
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/* Read command line */
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if (emit_prompt) {
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printf("%s", prompt);
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fflush(stdout);
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}
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if ((fgets(cmdline, MAXLINE, stdin) == NULL) && ferror(stdin))
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app_error("fgets error");
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if (feof(stdin)) { /* End of file (ctrl-d) */
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fflush(stdout);
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exit(0);
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}
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/* Evaluate the command line */
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eval(cmdline);
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fflush(stdout);
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fflush(stdout);
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}
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exit(0); /* control never reaches here */
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}
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/*
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* eval - Evaluate the command line that the user has just typed in
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*
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* If the user has requested a built-in command (quit, jobs, bg or fg)
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* then execute it immediately. Otherwise, fork a child process and
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* run the job in the context of the child. If the job is running in
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* the foreground, wait for it to terminate and then return. Note:
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* each child process must have a unique process group ID so that our
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* background children don't receive SIGINT (SIGTSTP) from the kernel
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* when we type ctrl-c (ctrl-z) at the keyboard.
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*/
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void eval(char *cmdline)
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{
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char *argv[MAXARGS];
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char buf[MAXLINE]; // command will be parsed and modified?
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int bg; // whether it runs in background
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pid_t pid;
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sigset_t mask;
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sigemptyset(&mask);
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// preprocess cmd line
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strcpy(buf, cmdline);
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bg = parseline(buf, argv); // convert the command into argv
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if (argv[0] == NULL) // the line is empty, return
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{
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return;
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}
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// run external command
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if (!builtin_cmd(argv)) // built-in command is done in `builtin_cmd`
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{
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sigaddset(&mask, SIGCHLD);
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sigprocmask(SIG_BLOCK, &mask, NULL); // 5. block SIGCHLD
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if ((pid = fork()) == 0) // this is child
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{
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sigprocmask(SIG_UNBLOCK, &mask, NULL); // 5. unblock SIGCHLD
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setpgid(0, 0); // put the child process (0=current) into a new process group (0=current)
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if (execve(argv[0], argv, environ) < 0) // execute command failed
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{
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printf("%s: Command not found\n", argv[0]);
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exit(0); // here only child exited
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}
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}
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addjob(jobs, pid, bg ? BG : FG, cmdline); // add the job to job list.
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// When bg=1, state=2; bg=0, state=1. this way it's just elegant
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sigprocmask(SIG_UNBLOCK, &mask, NULL); // 5. unblock SIGCHLD
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if (!bg) // run the process in foreground:
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// wait for foreground job to terminate
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{
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waitfg(pid); // the waiting stuff should be done in `waitfg`
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}
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else
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{
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printf("[%d] (%d) %s", pid2jid(pid), pid, cmdline); // background job information
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}
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}
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return;
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}
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/*
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* parseline - Parse the command line and build the argv array.
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*
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* Characters enclosed in single quotes are treated as a single
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* argument. Return true if the user has requested a BG job, false if
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* the user has requested a FG job.
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*/
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int parseline(const char *cmdline, char **argv)
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{
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static char array[MAXLINE]; /* holds local copy of command line */
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char *buf = array; /* ptr that traverses command line */
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char *delim; /* points to first space delimiter */
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int argc; /* number of args */
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int bg; /* background job? */
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strcpy(buf, cmdline);
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buf[strlen(buf)-1] = ' '; /* replace trailing '\n' with space */
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while (*buf && (*buf == ' ')) /* ignore leading spaces */
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buf++;
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/* Build the argv list */
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argc = 0;
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if (*buf == '\'') {
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buf++;
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delim = strchr(buf, '\'');
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}
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else {
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delim = strchr(buf, ' ');
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}
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while (delim) {
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argv[argc++] = buf;
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*delim = '\0';
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buf = delim + 1;
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while (*buf && (*buf == ' ')) /* ignore spaces */
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buf++;
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if (*buf == '\'') {
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buf++;
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delim = strchr(buf, '\'');
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}
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else {
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delim = strchr(buf, ' ');
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}
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}
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argv[argc] = NULL;
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if (argc == 0) /* ignore blank line */
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return 1;
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/* should the job run in the background? */
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if ((bg = (*argv[argc-1] == '&')) != 0) {
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argv[--argc] = NULL;
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}
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return bg;
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}
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/*
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* builtin_cmd - If the user has typed a built-in command then execute
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* it immediately.
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*/
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int builtin_cmd(char **argv)
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{
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if (strcmp(argv[0], "quit") == 0) // process quit command
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{
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exit(0);
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}
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if (strcmp(argv[0], "jobs") == 0) // t5: process jobs command
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{
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listjobs(jobs);
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return 1; // this IS a builtin command, return 1 to notify
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}
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return 0; /* not a builtin command */
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}
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/*
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* do_bgfg - Execute the builtin bg and fg commands
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*/
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void do_bgfg(char **argv)
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{
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return;
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}
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/*
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* waitfg - Block until process pid is no longer the foreground process
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*/
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void waitfg(pid_t pid)
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{
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while (pid == fgpid(jobs))
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{
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sleep(0);
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}
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return;
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}
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/*****************
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* Signal handlers
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*****************/
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/*
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* sigchld_handler - The kernel sends a SIGCHLD to the shell whenever
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* a child job terminates (becomes a zombie), or stops because it
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* received a SIGSTOP or SIGTSTP signal. The handler reaps all
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* available zombie children, but doesn't wait for any other
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* currently running children to terminate.
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*/
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void sigchld_handler(int sig)
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{
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pid_t pid;
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int status;
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while((pid=waitpid(-1,&status,WNOHANG|WUNTRACED))>0) // check if a child has become zombie, without wait
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{
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if(WIFEXITED(status))
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{
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deletejob(jobs,pid); // remove pid from job list
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}
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if (WIFSIGNALED(status)) // SIGINT, etc.
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{
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printf("Job [%d] (%d) terminated by signal %d\n", pid2jid(pid), pid, WTERMSIG(status));
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deletejob(jobs, pid);
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}
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if (WIFSTOPPED(status)) // SIGTSTP, etc.
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{
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printf("Job [%d] (%d) stopped by signal %d\n", pid2jid(pid), pid, WSTOPSIG(status));
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struct job_t *job = getjobpid(jobs, pid);
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job->state = ST;
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}
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}
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if (pid < 0 && errno != ECHILD)
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{
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unix_error("waitpid error");
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}
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return;
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}
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/*
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* sigint_handler - The kernel sends a SIGINT to the shell whenver the
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* user types ctrl-c at the keyboard. Catch it and send it along
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* to the foreground job.
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*/
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void sigint_handler(int sig)
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{
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pid_t pid = fgpid(jobs); // get pid of foreground job
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if (pid != 0) // if no foreground job (PID=0), do nothing (ONLY send to foreground)
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{
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if (kill(-pid, SIGINT) < 0) // try to send SIGINT
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{
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unix_error("sigint error"); // failed
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}
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}
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return;
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}
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/*
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* sigtstp_handler - The kernel sends a SIGTSTP to the shell whenever
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* the user types ctrl-z at the keyboard. Catch it and suspend the
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* foreground job by sending it a SIGTSTP.
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*/
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void sigtstp_handler(int sig)
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{
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pid_t pid = fgpid(jobs);
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if (pid != 0)
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{
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if (kill(-pid, SIGTSTP) < 0)
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{
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unix_error("sigtstp error");
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}
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}
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return;
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}
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/*********************
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* End signal handlers
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*********************/
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/***********************************************
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* Helper routines that manipulate the job list
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**********************************************/
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/* clearjob - Clear the entries in a job struct */
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void clearjob(struct job_t *job) {
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job->pid = 0;
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job->jid = 0;
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job->state = UNDEF;
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job->cmdline[0] = '\0';
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}
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/* initjobs - Initialize the job list */
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void initjobs(struct job_t *jobs) {
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int i;
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for (i = 0; i < MAXJOBS; i++)
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clearjob(&jobs[i]);
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}
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/* maxjid - Returns largest allocated job ID */
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int maxjid(struct job_t *jobs)
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{
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int i, max=0;
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for (i = 0; i < MAXJOBS; i++)
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if (jobs[i].jid > max)
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max = jobs[i].jid;
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return max;
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}
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/* addjob - Add a job to the job list */
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int addjob(struct job_t *jobs, pid_t pid, int state, char *cmdline)
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{
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int i;
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if (pid < 1)
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return 0;
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for (i = 0; i < MAXJOBS; i++) {
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if (jobs[i].pid == 0) {
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jobs[i].pid = pid;
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jobs[i].state = state;
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jobs[i].jid = nextjid++;
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if (nextjid > MAXJOBS)
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nextjid = 1;
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strcpy(jobs[i].cmdline, cmdline);
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if(verbose){
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printf("Added job [%d] %d %s\n", jobs[i].jid, jobs[i].pid, jobs[i].cmdline);
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}
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return 1;
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}
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}
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printf("Tried to create too many jobs\n");
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return 0;
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}
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/* deletejob - Delete a job whose PID=pid from the job list */
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int deletejob(struct job_t *jobs, pid_t pid)
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{
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int i;
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if (pid < 1)
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return 0;
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for (i = 0; i < MAXJOBS; i++) {
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if (jobs[i].pid == pid) {
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clearjob(&jobs[i]);
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nextjid = maxjid(jobs)+1;
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return 1;
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}
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}
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return 0;
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}
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/* fgpid - Return PID of current foreground job, 0 if no such job */
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pid_t fgpid(struct job_t *jobs) {
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int i;
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for (i = 0; i < MAXJOBS; i++)
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if (jobs[i].state == FG)
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return jobs[i].pid;
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return 0;
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}
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/* getjobpid - Find a job (by PID) on the job list */
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struct job_t *getjobpid(struct job_t *jobs, pid_t pid) {
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int i;
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if (pid < 1)
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return NULL;
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for (i = 0; i < MAXJOBS; i++)
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if (jobs[i].pid == pid)
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return &jobs[i];
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return NULL;
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}
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/* getjobjid - Find a job (by JID) on the job list */
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struct job_t *getjobjid(struct job_t *jobs, int jid)
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{
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int i;
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if (jid < 1)
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return NULL;
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for (i = 0; i < MAXJOBS; i++)
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if (jobs[i].jid == jid)
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return &jobs[i];
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return NULL;
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}
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/* pid2jid - Map process ID to job ID */
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int pid2jid(pid_t pid)
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{
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int i;
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if (pid < 1)
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return 0;
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for (i = 0; i < MAXJOBS; i++)
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if (jobs[i].pid == pid) {
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return jobs[i].jid;
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}
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return 0;
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}
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/* listjobs - Print the job list */
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void listjobs(struct job_t *jobs)
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{
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int i;
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for (i = 0; i < MAXJOBS; i++) {
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if (jobs[i].pid != 0) {
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printf("[%d] (%d) ", jobs[i].jid, jobs[i].pid);
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switch (jobs[i].state) {
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case BG:
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printf("Running ");
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break;
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case FG:
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printf("Foreground ");
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break;
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case ST:
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printf("Stopped ");
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break;
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default:
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printf("listjobs: Internal error: job[%d].state=%d ",
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i, jobs[i].state);
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}
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printf("%s", jobs[i].cmdline);
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}
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}
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}
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/******************************
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* end job list helper routines
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******************************/
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/***********************
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* Other helper routines
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***********************/
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/*
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* usage - print a help message
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*/
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void usage(void)
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{
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printf("Usage: shell [-hvp]\n");
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printf(" -h print this message\n");
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printf(" -v print additional diagnostic information\n");
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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);
|
|
}
|
|
|
|
|
|
|