commands/nohup/nohup.c

   1 /*
   2  * Copyright (c) 2009, Erik van der Kouwe
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions are met:
   7  *
   8  * 1. Redistributions of source code must retain the above copyright notice,
   9  *    this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright notice,
  11  *    this list of conditions and the following disclaimer in the documentation
  12  *    and/or other materials provided with the distribution.
  13  * 3. The name of the author may not be used to endorse or promote products
  14  *    derived from this software without specific prior written permission.
  15  *
  16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
  17  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
  18  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
  19  * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  20  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  21  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
  22  * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
  23  * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
  24  * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
  25  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  26  */
  27
  28 /*
  29  * Functionality implemented according to this specification:
  30  * http://www.opengroup.org/onlinepubs/000095399/utilities/nohup.html
  31  */
  32
  33 #include <errno.h>
  34 #include <fcntl.h>
  35 #include <limits.h>
  36 #include <signal.h>
  37 #include <stdio.h>
  38 #include <stdlib.h>
  39 #include <sys/stat.h>
  40 #include <unistd.h>
  41
  42 #define NOHUP_OUT_FILENAME "nohup.out"
  43
  44 static void print_usage(const char *argv0)
  45 {
  46         printf("Usage: %s command [arg...]\n", argv0);
  47 }
  48
  49 static int redirect_tty(void)
  50 {
  51         int fd;
  52         char buffer[PATH_MAX + 1], *home;
  53
  54         /* redirect stdout to a file if needed */
  55         if (isatty(STDOUT_FILENO))
  56         {
  57                 /* first try: current directory */
  58                 fd = open(NOHUP_OUT_FILENAME, O_WRONLY | O_APPEND | O_CREAT, S_IRUSR | S_IWUSR);
  59                 if (fd < 0)
  60                 {
  61                         /* alternative: home directory */
  62                         home = getenv("HOME");
  63                         if (home)
  64                         {
  65                                 snprintf(buffer, sizeof(buffer), "%s/%s", home, NOHUP_OUT_FILENAME);
  66                                 buffer[sizeof(buffer) - 1] = 0;
  67                                 fd = open(buffer, O_WRONLY | O_APPEND | O_CREAT, S_IRUSR | S_IWUSR);
  68                         }
  69                 }
  70
  71                 if (fd < 0)
  72                 {
  73                         perror("cannot create " NOHUP_OUT_FILENAME " and $HOME/" NOHUP_OUT_FILENAME);
  74                         return -1;
  75                 }
  76
  77                 /* move the fd to stdout */
  78                 if (dup2(fd, STDOUT_FILENO) < 0 || close(fd) < 0)
  79                 {
  80                         perror("cannot redirect stdout");
  81                         return -1;
  82                 }
  83         }
  84
  85         /* redirect stderr to stdout if needed */
  86         if (isatty(STDERR_FILENO))
  87         {
  88                 if (dup2(STDOUT_FILENO, STDERR_FILENO) < 0)
  89                 {
  90                         perror("cannot redirect stderr");
  91                         return -1;
  92                 }
  93         }
  94
  95         return 0;
  96 }
  97
  98 int main(int argc, char **argv)
  99 {
 100         struct sigaction sa;
 101
 102         /* check parameters */
 103         if (argc < 2)
 104         {
 105                 print_usage(argv[0]);
 106                 return 127;
 107         }
 108
 109         /* ignore SIGHUP */
 110         sa.sa_handler = SIG_IGN;
 111         sigemptyset(&sa.sa_mask);
 112         sa.sa_flags = 0;
 113         if (sigaction(SIGHUP, &sa, NULL) < 0)
 114         {
 115                 perror("cannot ignore SIGHUP");
 116                 return 127;
 117         }
 118
 119         /* redirect TTY input and output */
 120         if (redirect_tty() < 0)
 121                 return 127;
 122
 123         /* run the command */
 124         execvp(argv[1], argv + 1);
 125         perror("cannot execute");
 126
 127         /* exit code depends on whether the utility was found */
 128         switch (errno)
 129         {
 130                 case ELOOP:
 131                 case ENAMETOOLONG:
 132                 case ENOENT:
 133                 case ENOTDIR:
 134                         /* utility not found */
 135                         return 127;
 136
 137                 default:
 138                         /* exec failed for other reason */
 139                         return 126;
 140         }
 141 }