fixincludes/procopen.c

   1
   2 /*
   3  *  server.c  Set up and handle communications with a server process.
   4  *
   5  *  Server Handling copyright 1992-1999, 2004 The Free Software Foundation
   6  *
   7  *  Server Handling is free software.
   8  *  You may redistribute it and/or modify it under the terms of the
   9  *  GNU General Public License, as published by the Free Software
  10  *  Foundation; either version 2, or (at your option) any later version.
  11  *
  12  *  Server Handling is distributed in the hope that it will be useful,
  13  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  *  GNU General Public License for more details.
  16  *
  17  *  You should have received a copy of the GNU General Public License
  18  *  along with Server Handling.  See the file "COPYING".  If not,
  19  *  write to:  The Free Software Foundation, Inc.,
  20  *             51 Franklin Street, Fifth Floor,
  21  *             Boston,  MA  02110-1301, USA.
  22  *
  23  * As a special exception, The Free Software Foundation gives
  24  * permission for additional uses of the text contained in his release
  25  * of ServerHandler.
  26  *
  27  * The exception is that, if you link the ServerHandler library with other
  28  * files to produce an executable, this does not by itself cause the
  29  * resulting executable to be covered by the GNU General Public License.
  30  * Your use of that executable is in no way restricted on account of
  31  * linking the ServerHandler library code into it.
  32  *
  33  * This exception does not however invalidate any other reasons why
  34  * the executable file might be covered by the GNU General Public License.
  35  *
  36  * This exception applies only to the code released by The Free
  37  * Software Foundation under the name ServerHandler.  If you copy code
  38  * from other sources under the General Public License into a copy of
  39  * ServerHandler, as the General Public License permits, the exception
  40  * does not apply to the code that you add in this way.  To avoid
  41  * misleading anyone as to the status of such modified files, you must
  42  * delete this exception notice from them.
  43  *
  44  * If you write modifications of your own for ServerHandler, it is your
  45  * choice whether to permit this exception to apply to your modifications.
  46  * If you do not wish that, delete this exception notice.
  47  */
  48
  49 #include "fixlib.h"
  50 #include "server.h"
  51
  52 STATIC const char* def_args[] =
  53 { (char *) NULL, (char *) NULL };
  54
  55 /*
  56  *  chain_open
  57  *
  58  *  Given an FD for an inferior process to use as stdin,
  59  *  start that process and return a NEW FD that that process
  60  *  will use for its stdout.  Requires the argument vector
  61  *  for the new process and, optionally, a pointer to a place
  62  *  to store the child's process id.
  63  */
  64 int
  65 chain_open (int stdin_fd, tCC** pp_args, pid_t* p_child)
  66 {
  67   t_fd_pair stdout_pair;
  68   pid_t ch_id;
  69   tCC *pz_cmd;
  70
  71   stdout_pair.read_fd = stdout_pair.write_fd = -1;
  72
  73   /*
  74    *  Create a pipe it will be the child process' stdout,
  75    *  and the parent will read from it.
  76    */
  77   if (pipe ((int *) &stdout_pair) < 0)
  78     {
  79       if (p_child != (pid_t *) NULL)
  80         *p_child = NOPROCESS;
  81       return -1;
  82     }
  83
  84   /*
  85    *  If we did not get an arg list, use the default
  86    */
  87   if (pp_args == (tCC **) NULL)
  88     pp_args = def_args;
  89
  90   /*
  91    *  If the arg list does not have a program,
  92    *  assume the "SHELL" from the environment, or, failing
  93    *  that, then sh.  Set argv[0] to whatever we decided on.
  94    */
  95   if (pz_cmd = *pp_args,
  96       (pz_cmd == (char *) NULL) || (*pz_cmd == '\0'))
  97     {
  98
  99       pz_cmd = getenv ("SHELL");
 100       if (pz_cmd == (char *) NULL)
 101         pz_cmd = "sh";
 102     }
 103
 104 #ifdef DEBUG_PRINT
 105   printf ("START:  %s\n", pz_cmd);
 106   {
 107     int idx = 0;
 108
 109     while (pp_args[++idx] != (char *) NULL)
 110       printf ("  ARG %2d:  %s\n", idx, pp_args[idx]);
 111   }
 112 #endif
 113
 114   /*
 115    *  Call fork() and see which process we become
 116    */
 117   ch_id = fork ();
 118   switch (ch_id)
 119     {
 120     case NOPROCESS:             /* parent - error in call */
 121       close (stdout_pair.read_fd);
 122       close (stdout_pair.write_fd);
 123       if (p_child != (pid_t *) NULL)
 124         *p_child = NOPROCESS;
 125       return -1;
 126
 127     default:                    /* parent - return opposite FD's */
 128       if (p_child != (pid_t *) NULL)
 129         *p_child = ch_id;
 130 #ifdef DEBUG_PRINT
 131       printf ("for pid %d:  stdin from %d, stdout to %d\n"
 132               "for parent:  read from %d\n",
 133               ch_id, stdin_fd, stdout_pair.write_fd, stdout_pair.read_fd);
 134 #endif
 135       close (stdin_fd);
 136       close (stdout_pair.write_fd);
 137       return stdout_pair.read_fd;
 138
 139     case NULLPROCESS:           /* child - continue processing */
 140       break;
 141     }
 142
 143   /*
 144    *  Close the pipe end handed back to the parent process
 145    */
 146   close (stdout_pair.read_fd);
 147
 148   /*
 149    *  Close our current stdin and stdout
 150    */
 151   close (STDIN_FILENO);
 152   close (STDOUT_FILENO);
 153
 154   /*
 155    *  Make the fd passed in the stdin, and the write end of
 156    *  the new pipe become the stdout.
 157    */
 158   dup2 (stdout_pair.write_fd, STDOUT_FILENO);
 159   dup2 (stdin_fd, STDIN_FILENO);
 160
 161   if (*pp_args == (char *) NULL)
 162     *pp_args = pz_cmd;
 163
 164   execvp (pz_cmd, (char**)pp_args);
 165   fprintf (stderr, "Error %d:  Could not execvp( '%s', ... ):  %s\n",
 166            errno, pz_cmd, xstrerror (errno));
 167   exit (EXIT_PANIC);
 168 }
 169
 170
 171 /*
 172  *  proc2_open
 173  *
 174  *  Given a pointer to an argument vector, start a process and
 175  *  place its stdin and stdout file descriptors into an fd pair
 176  *  structure.  The "write_fd" connects to the inferior process
 177  *  stdin, and the "read_fd" connects to its stdout.  The calling
 178  *  process should write to "write_fd" and read from "read_fd".
 179  *  The return value is the process id of the created process.
 180  */
 181 pid_t
 182 proc2_open (t_fd_pair* p_pair, tCC** pp_args)
 183 {
 184   pid_t ch_id;
 185
 186   /*  Create a bi-directional pipe.  Writes on 0 arrive on 1 and vice
 187      versa, so the parent and child processes will read and write to
 188      opposite FD's.  */
 189   if (pipe ((int *) p_pair) < 0)
 190     return NOPROCESS;
 191
 192   p_pair->read_fd = chain_open (p_pair->read_fd, pp_args, &ch_id);
 193   if (ch_id == NOPROCESS)
 194     close (p_pair->write_fd);
 195
 196   return ch_id;
 197 }
 198
 199
 200 /*
 201  *  proc2_fopen
 202  *
 203  *  Identical to "proc2_open()", except that the "fd"'s are
 204  *  "fdopen(3)"-ed into file pointers instead.
 205  */
 206 pid_t
 207 proc2_fopen (t_pf_pair* pf_pair, tCC** pp_args)
 208 {
 209   t_fd_pair fd_pair;
 210   pid_t ch_id = proc2_open (&fd_pair, pp_args);
 211
 212   if (ch_id == NOPROCESS)
 213     return ch_id;
 214
 215   pf_pair->pf_read = fdopen (fd_pair.read_fd, "r");
 216   pf_pair->pf_write = fdopen (fd_pair.write_fd, "w");
 217   return ch_id;
 218 }