exec.c

   1 /** \file exec.c Helper functions for spawning new processes. */
   2
   3 #include <string.h>
   4 #include <sys/types.h>
   5 #include <sys/stat.h>
   6 #include <fcntl.h>
   7 #include <unistd.h>
   8 #include <assert.h>
   9 #include <stdlib.h>
  10 #include <signal.h>
  11
  12
  13 #include "gcc-compat.h"
  14 #include "error.h"
  15 #include "string.h"
  16
  17
  18 /**
  19  * Spawn a new process and redirect fd 0, 1, and 2.
  20  *
  21  * \param pid Will hold the pid of the created process upon return.
  22  * \param file Path of the executable to execute.
  23  * \param args The argument array for the command.
  24  * \param fds a Pointer to a value-result array.
  25  *
  26  * \return Standard.
  27  *
  28  * \sa null(4), pipe(2), dup2(2), fork(2), exec(3).
  29  */
  30 int dss_exec(pid_t *pid, const char *file, char *const *const args, int *fds)
  31 {
  32         int ret, in[2] = {-1, -1}, out[2] = {-1, -1}, err[2] = {-1, -1},
  33                 null = -1; /* ;) */
  34
  35         ret = -E_DUP_PIPE;
  36         if (fds[0] > 0 && pipe(in) < 0)
  37                 goto err_out;
  38         if (fds[1] > 0 && pipe(out) < 0)
  39                 goto err_out;
  40         if (fds[2] > 0 && pipe(err) < 0)
  41                 goto err_out;
  42         if (!fds[0] || !fds[1] || !fds[2]) {
  43                 ret = -E_NULL_OPEN;
  44                 null = open("/dev/null", O_RDONLY);
  45                 if (null < 0)
  46                         goto err_out;
  47         }
  48         if ((*pid = fork()) < 0)
  49                 exit(EXIT_FAILURE);
  50         if (!(*pid)) { /* child */
  51                 if (fds[0] >= 0) {
  52                         if (fds[0]) {
  53                                 close(in[1]);
  54                                 if (in[0] != STDIN_FILENO)
  55                                         dup2(in[0], STDIN_FILENO);
  56                         } else
  57                                 dup2(null, STDIN_FILENO);
  58                 }
  59                 if (fds[1] >= 0) {
  60                         if (fds[1]) {
  61                                 close(out[0]);
  62                                 if (out[1] != STDOUT_FILENO)
  63                                         dup2(out[1], STDOUT_FILENO);
  64                         } else
  65                                 dup2(null, STDOUT_FILENO);
  66                 }
  67                 if (fds[2] >= 0) {
  68                         if (fds[2]) {
  69                                 close(err[0]);
  70                                 if (err[1] != STDERR_FILENO)
  71                                         dup2(err[1], STDERR_FILENO);
  72                         } else
  73                                 dup2(null, STDERR_FILENO);
  74                 }
  75                 if (null >= 0)
  76                         close(null);
  77                 signal(SIGINT, SIG_DFL);
  78                 signal(SIGTERM, SIG_DFL);
  79                 signal(SIGCHLD, SIG_DFL);
  80                 execvp(file, args);
  81                 _exit(EXIT_FAILURE);
  82         }
  83         if (fds[0] > 0) {
  84                 close(in[0]);
  85                 *fds = in[1];
  86         }
  87         if (fds[1] > 0) {
  88                 close(out[1]);
  89                 *(fds + 1) = out[0];
  90         }
  91         if (fds[2] > 0) {
  92                 close(err[1]);
  93                 *(fds + 2) = err[0];
  94         }
  95         if (null >= 0)
  96                 close(null);
  97         return 1;
  98 err_out:
  99         make_err_msg("failed to exec %s", file);
 100         if (err[0] >= 0)
 101                 close(err[0]);
 102         if (err[1] >= 0)
 103                 close(err[1]);
 104         if (out[0] >= 0)
 105                 close(out[0]);
 106         if (out[1] >= 0)
 107                 close(out[1]);
 108         if (in[0] >= 0)
 109                 close(in[0]);
 110         if (in[1] >= 0)
 111                 close(in[1]);
 112         if (null >= 0)
 113                 close(null);
 114         return ret;
 115 }