exec.c

   1 /* Copyright (C) 2003 Andre Noll <maan@tuebingen.mpg.de>, see file COPYING. */
   2
   3 /** \file exec.c Helper functions for spawning new processes. */
   4
   5 #include <regex.h>
   6
   7 #include "para.h"
   8 #include "error.h"
   9 #include "fd.h"
  10 #include "string.h"
  11
  12 /**
  13  * Spawn a new process and redirect fd 0, 1, and 2.
  14  *
  15  * \param pid Will hold the pid of the created process upon return.
  16  * \param file Path of the executable to execute.
  17  * \param args The argument array for the command.
  18  * \param fds a Pointer to a value-result array.
  19  *
  20  * \return Standard.
  21  *
  22  * \sa null(4), pipe(2), dup2(2), fork(2), exec(3).
  23  */
  24 static int para_exec(pid_t *pid, const char *file, char *const *const args, int *fds)
  25 {
  26         int ret, in[2] = {-1, -1}, out[2] = {-1, -1}, err[2] = {-1, -1},
  27                 null = -1; /* ;) */
  28
  29         ret = -E_DUP_PIPE;
  30         if (fds[0] > 0 && pipe(in) < 0)
  31                 goto err_out;
  32         if (fds[1] > 0 && pipe(out) < 0)
  33                 goto err_out;
  34         if (fds[2] > 0 && pipe(err) < 0)
  35                 goto err_out;
  36         if (!fds[0] || !fds[1] || !fds[2]) {
  37                 ret = para_open("/dev/null", O_RDWR, 42);
  38                 if (ret < 0)
  39                         goto err_out;
  40                 null = ret;
  41         }
  42         ret = fork();
  43         if (ret < 0) {
  44                 ret = -ERRNO_TO_PARA_ERROR(errno);
  45                 goto err_out;
  46         }
  47         *pid = ret;
  48         if (!(*pid)) { /* child */
  49                 if (fds[0] >= 0) {
  50                         if (fds[0]) {
  51                                 close(in[1]);
  52                                 if (in[0] != STDIN_FILENO)
  53                                         dup2(in[0], STDIN_FILENO);
  54                         } else
  55                                 dup2(null, STDIN_FILENO);
  56                 }
  57                 if (fds[1] >= 0) {
  58                         if (fds[1]) {
  59                                 close(out[0]);
  60                                 if (out[1] != STDOUT_FILENO)
  61                                         dup2(out[1], STDOUT_FILENO);
  62                         } else
  63                                 dup2(null, STDOUT_FILENO);
  64                 }
  65                 if (fds[2] >= 0) {
  66                         if (fds[2]) {
  67                                 close(err[0]);
  68                                 if (err[1] != STDERR_FILENO)
  69                                         dup2(err[1], STDERR_FILENO);
  70                         } else
  71                                 dup2(null, STDERR_FILENO);
  72                 }
  73                 if (null >= 0)
  74                         close(null);
  75                 execvp(file, args);
  76                 _exit(EXIT_FAILURE);
  77         }
  78         if (fds[0] > 0) {
  79                 close(in[0]);
  80                 *fds = in[1];
  81         }
  82         if (fds[1] > 0) {
  83                 close(out[1]);
  84                 *(fds + 1) = out[0];
  85         }
  86         if (fds[2] > 0) {
  87                 close(err[1]);
  88                 *(fds + 2) = err[0];
  89         }
  90         if (null >= 0)
  91                 close(null);
  92         return 1;
  93 err_out:
  94         if (err[0] >= 0)
  95                 close(err[0]);
  96         if (err[1] >= 0)
  97                 close(err[1]);
  98         if (out[0] >= 0)
  99                 close(out[0]);
 100         if (out[1] >= 0)
 101                 close(out[1]);
 102         if (in[0] >= 0)
 103                 close(in[0]);
 104         if (in[1] >= 0)
 105                 close(in[1]);
 106         if (null >= 0)
 107                 close(null);
 108         PARA_ERROR_LOG("%s\n", para_strerror(-ret));
 109         return ret;
 110 }
 111
 112 /**
 113  * Exec the given command.
 114  *
 115  * \param pid Will hold the pid of the created process upon return.
 116  * \param cmdline Holds the command and its arguments, separated by spaces.
 117  * \param fds A pointer to a value-result array.
 118  *
 119  * This function uses fork/exec to create a new process. \a fds must be a
 120  * pointer to three integers, corresponding to stdin, stdout and stderr
 121  * respectively. It specifies how to deal with fd 0, 1, 2 in the child. The
 122  * contents of \a fds are interpreted as follows:
 123  *
 124  *      - fd[i] < 0: leave fd \a i alone.
 125  *      - fd[i] = 0: dup fd \a i to \p /dev/null.
 126  *      - fd[i] > 0: create a pipe and dup i to one end of that pipe.
 127  *      Upon return, fd[i] contains the file descriptor of the pipe.
 128  *
 129  *      In any case, all unneeded file descriptors are closed.
 130  *
 131  * \return Standard.
 132  */
 133 int para_exec_cmdline_pid(pid_t *pid, const char *cmdline, int *fds)
 134 {
 135         int ret;
 136         char **argv;
 137
 138         ret = create_argv(cmdline, " \t", &argv);
 139         if (ret < 0)
 140                 return ret;
 141         ret = para_exec(pid, argv[0], argv, fds);
 142         free_argv(argv);
 143         return ret;
 144 }