/*
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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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/* Init */
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int bg;
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char buf[MAXLINE];
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char *argv[MAXARGS];
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pid_t pid;
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sigset_t mask;
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/* build argv first */
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strcpy(buf, cmdline);
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bg = parseline(buf, argv);
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if(!argv[0]) /* not found PATH */
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return;
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if(!builtin_cmd(argv)) {
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/* if builtin, exec and exit */
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sigemptyset(&mask); /* clear the set */
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sigaddset(&mask, SIGCHLD); /* add stop to mask first */
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sigprocmask(SIG_BLOCK, &mask, NULL); /* inorder to block the parent */
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if((pid = fork()) < 0) {
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unix_error("forking error");
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}
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else if(pid == 0){
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sigprocmask(SIG_UNBLOCK, &mask, NULL); /* set unblock */
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setpgid(0, 0); /* set group pid to 0 */
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/* if command not found, exit */
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if(execvp(argv[0], argv) < 0) {
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printf("%s: Command not found.\n", argv[0]);
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exit(1);
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}
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}
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/* command found */
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int state = bg ? BG : FG; /* background? foreground? */
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addjob(jobs, pid, state, cmdline); /* exec cmd ok -> job ready to go */
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sigprocmask(SIG_UNBLOCK, &mask, NULL); /* set unblock before exec */
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/*
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* From the Internet: 托管线程可以是后台线程,也可以是前台线程。
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* 后台线程和前台线程几乎完全相同,只有一处不同,即后台线程不会确保托管执行环境一直运行。
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* 一旦托管进程(其中 .exe 文件为托管程序集)中的所有前台线程都停止,系统会停止并关闭所有后台线程。
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*/
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if(!bg) /* foreground need to wait other fg */
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waitfg(pid);
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else /* background can exec */
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printf("[%d] (%d) %s", pid2jid(pid), pid, cmdline);
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}
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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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/* 1 - a cmd that can be exec, 0 - not */
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if(!argv[0]) { /* void cmd */
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return 1;
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}
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else if(!strcmp(argv[0], "&")) {
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return 1;
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}
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else if(!strcmp(argv[0], "jobs")) { /* cmd to list jobs */
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listjobs(jobs);
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return 1;
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}
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else if(!strcmp(argv[0], "quit")) { /* cmd to quit, nothing to exec, so return 0 */
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exit(0);
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}
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else if((!strcmp(argv[0], "bg")) || (!strcmp(argv[0], "fg"))) { /* cmd to exec fg/bg */
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do_bgfg(argv);
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return 1;
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}
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else{
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return 0; /* not a builtin command */
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}
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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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/* init */
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pid_t pid;
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int jid;
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struct job_t *job;
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if(!argv[1]) { /* have no PID/JID arguments */
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printf("%s command requires PID or %%jobid argument\n", argv[0]);
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return;
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}
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if(*argv[1] == '%') { /* %: need jid */
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jid = atoi(argv[1] + 1); /* get jid */
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if( (job = getjobjid(jobs, jid)) == 0 ) { /* illegal jid */
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printf("%s: No such job\n", argv[1]);
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return;
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}
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pid = job->pid; /* get job and pid */
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}
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else if(isdigit(*argv[1])) { /* if get a pid */
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pid = atoi(argv[1]); /* use pid(not %) */
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if( (job = getjobjid(jobs, jid)) == 0 ) { /* illegal pid */
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printf("(%d): No such process\n", pid);
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return;
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}
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}
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else {
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printf("%s: argument must be a PID or %%jobid\n", argv[0]);
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return;
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}
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if(!job) { /* illegal job */
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printf("Error -- no such job.\n");
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return;
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}
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if(!strcmp(argv[0], "bg")) { /* if background */
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kill(-pid, SIGCONT); /* SIGCONT -- continue to exec */
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job->state = BG; /* state to BG(background) */
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printf("[%d] (%d) %s", job->jid, pid, job->cmdline);
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}
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else { /* if foreground */
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kill(-pid, SIGCONT); /* SIGCONT -- continue to exec */
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job->state = FG; /* state to FG(foreground) */
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waitfg(pid); /* need to wait other FGs */
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}
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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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if(pid == 0)
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return;
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/*
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* From the Internet:Thread.Sleep(0) 并非是真的要线程挂起0毫秒,意义在于这次调用Thread.Sleep(0)的当前线程确实的被冻结了一下,让其他线程有机会优先执行。
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* Thread.Sleep(0) 是你的线程暂时放弃cpu,也就是释放一些未用的时间片给其他线程或进程使用,就相当于一个让位动作。
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*/
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while(pid == fgpid(jobs))
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sleep(0);
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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(fgpid(jobs), &status, WNOHANG|WUNTRACED)) > 0) {
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/* WNOHANG 若pid指定的子进程没有结束,则waitpid()函数返回0,不予以等待。若结束,则返回该子进程的ID。*/
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/* WUNTRACED 若子进程进入暂停状态,则马上返回,但子进程的结束状态不予以理会。WIFSTOPPED(status)宏确定返回值是否对应与一个暂停子进程。*/
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if (WIFSTOPPED(status)){ /* if stopped */
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getjobpid(jobs, pid)->state = ST; /* change state to ST(stopped) */
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int jid = pid2jid(pid);
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printf("Job [%d] (%d) Stopped by signal %d\n", jid, pid, WSTOPSIG(status));
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}
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else if (WIFSIGNALED(status)){ /* if signaled */
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int jid = pid2jid(pid); /* delete */
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printf("Job [%d] (%d) terminated by signal %d\n", jid, pid, WTERMSIG(status));
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deletejob(jobs, pid);
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}
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else if (WIFEXITED(status)){ /* if exited */
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deletejob(jobs, pid);
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}
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else;
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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;
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if( (pid = fgpid(jobs)) <= 0)
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return; /* illegal pid */
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kill(-pid, sig);
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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;
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if ((pid = fgpid(jobs)) <= 0)
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return; /* illegal pid */
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kill(-pid, sig);
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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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|
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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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|
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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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|
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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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|
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if (pid < 1)
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return 0;
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|
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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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|
|
/* 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);
|
|
}
|