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