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307 lines
8.5 KiB
C
307 lines
8.5 KiB
C
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/*
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* server.c Set up and handle communications with a server process.
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*
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* Server Handling copyright 1992-1999, 2001 The Free Software Foundation
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*
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* Server Handling is free software.
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* You may redistribute it and/or modify it under the terms of the
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* GNU General Public License, as published by the Free Software
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* Foundation; either version 2, or (at your option) any later version.
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*
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* Server Handling is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with Server Handling. See the file "COPYING". If not,
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* write to: The Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor,
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* Boston, MA 02110-1301, USA.
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*
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* As a special exception, The Free Software Foundation gives
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* permission for additional uses of the text contained in his release
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* of ServerHandler.
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*
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* The exception is that, if you link the ServerHandler library with other
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* files to produce an executable, this does not by itself cause the
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* resulting executable to be covered by the GNU General Public License.
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* Your use of that executable is in no way restricted on account of
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* linking the ServerHandler library code into it.
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*
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* This exception does not however invalidate any other reasons why
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* the executable file might be covered by the GNU General Public License.
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*
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* This exception applies only to the code released by The Free
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* Software Foundation under the name ServerHandler. If you copy code
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* from other sources under the General Public License into a copy of
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* ServerHandler, as the General Public License permits, the exception
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* does not apply to the code that you add in this way. To avoid
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* misleading anyone as to the status of such modified files, you must
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* delete this exception notice from them.
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*
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* If you write modifications of your own for ServerHandler, it is your
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* choice whether to permit this exception to apply to your modifications.
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* If you do not wish that, delete this exception notice.
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*/
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#include "fixlib.h"
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#include "server.h"
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STATIC volatile enum t_bool read_pipe_timeout;
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STATIC pid_t server_master_pid = NOPROCESS;
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tSCC* def_args[] =
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{ (char *) NULL, (char *) NULL };
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STATIC t_pf_pair server_pair =
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{ (FILE *) NULL, (FILE *) NULL };
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STATIC pid_t server_id = NULLPROCESS;
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/*
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* Arbitrary text that should not be found in the shell output.
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* It must be a single line and appear verbatim at the start of
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* the terminating output line.
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*/
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tSCC z_done[] = "ShElL-OuTpUt-HaS-bEeN-cOmPlEtEd";
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tSCC* p_cur_dir = (char *) NULL;
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/*
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* load_data
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*
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* Read data from a file pointer (a pipe to a process in this context)
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* until we either get EOF or we get a marker line back.
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* The read data are stored in a malloc-ed string that is truncated
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* to size at the end. Input is assumed to be an ASCII string.
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*/
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static char *
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load_data (FILE* fp)
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{
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char *pz_text;
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size_t text_size;
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char *pz_scan;
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char z_line[1024];
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t_bool got_done = BOOL_FALSE;
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text_size = sizeof (z_line) * 2;
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pz_scan = pz_text = XNEWVEC (char, text_size);
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for (;;)
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{
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size_t used_ct;
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alarm (10);
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read_pipe_timeout = BOOL_FALSE;
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if (fgets (z_line, sizeof (z_line), fp) == (char *) NULL)
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break;
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if (strncmp (z_line, z_done, sizeof (z_done) - 1) == 0)
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{
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got_done = BOOL_TRUE;
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break;
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}
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strcpy (pz_scan, z_line);
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pz_scan += strlen (z_line);
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used_ct = (size_t) (pz_scan - pz_text);
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if (text_size - used_ct < sizeof (z_line))
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{
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size_t off = (size_t) (pz_scan - pz_text);
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text_size += 4096;
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pz_text = XRESIZEVEC (char, pz_text, text_size);
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pz_scan = pz_text + off;
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}
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}
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alarm (0);
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if (read_pipe_timeout || ! got_done)
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{
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free ((void *) pz_text);
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return (char *) NULL;
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}
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while ((pz_scan > pz_text) && ISSPACE (pz_scan[-1]))
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pz_scan--;
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*pz_scan = NUL;
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return XRESIZEVEC (char, pz_text, strlen (pz_text) + 1);
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}
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/*
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* close_server
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*
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* Make certain the server process is dead, close the
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* pipes to it and from it, finally NULL out the file pointers
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*/
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void
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close_server (void)
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{
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if ( (server_id != NULLPROCESS)
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&& (server_master_pid == getpid ()))
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{
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kill ((pid_t) server_id, SIGKILL);
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server_id = NULLPROCESS;
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server_master_pid = NOPROCESS;
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fclose (server_pair.pf_read);
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fclose (server_pair.pf_write);
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server_pair.pf_read = server_pair.pf_write = (FILE *) NULL;
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}
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}
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/*
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* sig_handler really only handles the timeout and pipe signals.
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* This ensures that we do not wait forever on a request
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* to our server, and also that if the server dies, we do not
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* die from a sigpipe problem.
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*/
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static void
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sig_handler (int signo ATTRIBUTE_UNUSED)
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{
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#ifdef DEBUG
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/* FIXME: this is illegal to do in a signal handler. */
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fprintf (stderr,
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"fixincl ERROR: sig_handler: killed pid %ld due to %s\n",
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(long) server_id, signo == SIGPIPE ? "SIGPIPE" : "SIGALRM");
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#endif
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close_server ();
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read_pipe_timeout = BOOL_TRUE;
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}
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/*
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* server_setup Establish the signal handler for PIPE and ALARM.
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* Also establishes the current directory to give to the
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* server process at the start of every server command.
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*/
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static void
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server_setup (void)
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{
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static int atexit_done = 0;
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char buff [MAXPATHLEN + 1];
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if (atexit_done++ == 0)
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atexit (close_server);
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else
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fputs ("NOTE: server restarted\n", stderr);
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server_master_pid = getpid ();
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signal (SIGPIPE, sig_handler);
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signal (SIGALRM, sig_handler);
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fputs ("trap : 1\n", server_pair.pf_write);
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fflush (server_pair.pf_write);
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if (getcwd (buff, MAXPATHLEN + 1) == NULL)
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buff[0] = 0;
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p_cur_dir = xstrdup (buff);
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}
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/*
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* find_shell
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*
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* Locate a shell suitable for use. For various reasons
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* (like the use of "trap" in server_setup(), it must be a
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* Bourne-like shell.
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*
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* Most of the time, /bin/sh is preferred, but sometimes
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* it's quite broken (like on Ultrix). autoconf lets you
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* override with $CONFIG_SHELL, so we do the same.
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*/
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static const char *
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find_shell (void)
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{
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char * shell = getenv ("CONFIG_SHELL");
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if (shell)
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return shell;
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return "/bin/sh";
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}
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/*
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* run_shell
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*
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* Run a shell command on the server. The command string
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* passed in is wrapped inside the sequence:
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*
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* cd <original directory>
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* <command string>
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* echo
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* echo <end-of-command-marker>
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*
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* This ensures that all commands start at a known place in
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* the directory structure, that any incomplete output lines
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* are completed and that our special marker sequence appears on
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* a line by itself. We have chosen a marker that is
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* excessively unlikely to be reproduced in normal output:
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*
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* "ShElL-OuTpUt-HaS-bEeN-cOmPlEtEd"
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*/
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char *
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run_shell (const char* pz_cmd)
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{
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tSCC zNoServer[] = "Server not running, cannot run:\n%s\n\n";
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t_bool retry = BOOL_TRUE;
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do_retry:
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/* IF the shell server process is not running yet,
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THEN try to start it. */
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if (server_id == NULLPROCESS)
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{
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def_args[0] = find_shell ();
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server_id = proc2_fopen (&server_pair, def_args);
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if (server_id > 0)
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server_setup ();
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}
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/* IF it is still not running, THEN return the nil string. */
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if (server_id <= 0)
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{
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fprintf (stderr, zNoServer, pz_cmd);
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return XCNEW (char);
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}
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/* Make sure the process will pay attention to us, send the
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supplied command, and then have it output a special marker that
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we can find. */
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fprintf (server_pair.pf_write, "cd \"%s\"\n%s\n\necho\necho %s\n",
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p_cur_dir, pz_cmd, z_done);
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fflush (server_pair.pf_write);
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/* IF the server died and we received a SIGPIPE,
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THEN return an empty string. */
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if (server_id == NULLPROCESS)
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{
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fprintf (stderr, zNoServer, pz_cmd);
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return XCNEW (char);
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}
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/* Now try to read back all the data. If we fail due to either a
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sigpipe or sigalrm (timeout), we will return the nil string. */
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{
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char *pz = load_data (server_pair.pf_read);
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if (pz == (char *) NULL)
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{
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close_server ();
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if (retry)
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{
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retry = BOOL_FALSE;
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goto do_retry;
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}
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fprintf (stderr, "CLOSING SHELL SERVER - command failure:\n\t%s\n",
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pz_cmd);
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pz = XCNEW (char);
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}
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#ifdef DEBUG
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fprintf( stderr, "run_shell command success: %s\n", pz );
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#endif
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return pz;
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}
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}
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