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 }