dexec.c

用来编写 unix 环境下的守护程序的工具库

/* $Id: exec.c 31 2003-11-05 22:04:26Z lennart $ */

/*
 * This file is part of libdaemon.
 *
 * libdaemon is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * libdaemon is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with libdaemon; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <sys/types.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <sys/stat.h>
#include <stdlib.h>
#include <signal.h>
#include <sys/wait.h>
#include <limits.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdarg.h>
#include <assert.h>

#include "dlog.h"
#include "dsignal.h"
#include "dfork.h"

#include "dexec.h"

#define MAX_ARGS 100

int daemon_execv(const char *dir, int *ret, const char *prog, va_list ap) {
    pid_t pid;
    int p[2];
    unsigned n = 0;
    static char buf[256];
    int sigfd, r;
    fd_set fds;

    assert(daemon_signal_fd() >= 0);

    if (pipe(p) < 0) {
        daemon_log(LOG_ERR, "pipe() failed: %s", strerror(errno));
        return -1;
    }
    
    if ((pid = fork()) < 0) {
        daemon_log(LOG_ERR, "fork() failed: %s", strerror(errno));
        return -1;
        
    } else if (pid == 0) {
        char *args[MAX_ARGS];
        int i;
        
        if (p[1] != 1)
            dup2(p[1], 1);

        if (p[1] != 2)
            dup2(p[1], 2);
        
        if (p[0] > 2)
            close(p[0]);

        if (p[1] > 2)
            close(p[1]);

        close(0);
        if (open("/dev/null", O_RDONLY) != 0) {
            daemon_log(LOG_ERR, "Unable to open /dev/null as STDIN");
            _exit(EXIT_FAILURE);
        }

        daemon_close_all(-1);
        
	umask(0022); /* Set up a sane umask */
        
        if (dir && chdir(dir) < 0) {
            daemon_log(LOG_WARNING, "Failed to change to directory '%s'", dir);
            chdir("/");
        }
        
        for (i = 0; i < MAX_ARGS-1; i++)
            if (!(args[i] = va_arg(ap, char*)))
                break;
        args[i] = NULL;
        
        execv(prog, args);
        
        daemon_log(LOG_ERR, "execv(%s) failed: %s", prog, strerror(errno));
        
        _exit(EXIT_FAILURE);
    }
    
    close(p[1]);
    
    FD_ZERO(&fds);
    FD_SET(p[0], &fds);
    sigfd = daemon_signal_fd();
    FD_SET(sigfd, &fds);

    n = 0;

    for (;;) {
        fd_set qfds = fds;

        if (select(FD_SETSIZE, &qfds, NULL, NULL, NULL) < 0) {

            if (errno == EINTR)
                continue;

            daemon_log(LOG_ERR, "select() failed: %s", strerror(errno));
            return -1;
        }

        if (FD_ISSET(p[0], &qfds)) {
            char c;

            if (read(p[0], &c, 1) != 1)
                break;

            buf[n] = c;
            
            if (c == '\n' || n >= sizeof(buf) - 2) {
                if (c != '\n') n++;
                buf[n] = 0;

                if (buf[0]) 
                    daemon_log(LOG_INFO, "client: %s", buf); 
                
                n = 0;
            } else
                n++;
        }
        
        if (FD_ISSET(sigfd, &qfds)) {
            int sig;
            
            if ((sig = daemon_signal_next()) < 0) {
                daemon_log(LOG_ERR, "daemon_signal_next(): %s", strerror(errno));
                break;
            }
            
            if (sig != SIGCHLD) {
                daemon_log(LOG_WARNING, "Killing child.");
                kill(pid, SIGTERM);
            }
        }
    }
    
    if (n > 0) {
        buf[n] = 0;
        daemon_log(LOG_WARNING, "client: %s", buf); 
    }

    close(p[0]);
    
    for (;;) {
        if (waitpid(pid, &r, 0) < 0) {

            if (errno == EINTR)
                continue;

            daemon_log(LOG_ERR, "waitpid(): %s", strerror(errno));
            return -1;
        } else {
            if (!WIFEXITED(r))
                return -1;

            if (ret)
                *ret = WEXITSTATUS(r);

            return 0;
        }
    }
}

int daemon_exec(const char *dir, int *ret, const char *prog, ...) {
    va_list ap;
    int r;
    
    va_start(ap, prog);
    r = daemon_execv(dir, ret, prog, ap);
    va_end(ap);

    return r;
}