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
52STATIC 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 */
64int
65chain_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 */
181pid_t
182proc2_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 */
206pid_t
207proc2_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}
219