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1
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2 /*
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3 * server.c Set up and handle communications with a server process.
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4 *
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5 * Server Handling copyright 1992-1999, 2001 The Free Software Foundation
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6 *
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7 * Server Handling is free software.
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8 * You may redistribute it and/or modify it under the terms of the
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9 * GNU General Public License, as published by the Free Software
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10 * Foundation; either version 2, or (at your option) any later version.
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11 *
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12 * Server Handling is distributed in the hope that it will be useful,
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13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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15 * GNU General Public License for more details.
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16 *
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17 * You should have received a copy of the GNU General Public License
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18 * along with Server Handling. See the file "COPYING". If not,
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19 * write to: The Free Software Foundation, Inc.,
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20 * 51 Franklin Street, Fifth Floor,
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21 * Boston, MA 02110-1301, USA.
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22 *
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23 * As a special exception, The Free Software Foundation gives
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24 * permission for additional uses of the text contained in his release
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25 * of ServerHandler.
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26 *
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27 * The exception is that, if you link the ServerHandler library with other
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28 * files to produce an executable, this does not by itself cause the
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29 * resulting executable to be covered by the GNU General Public License.
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30 * Your use of that executable is in no way restricted on account of
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31 * linking the ServerHandler library code into it.
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32 *
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33 * This exception does not however invalidate any other reasons why
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34 * the executable file might be covered by the GNU General Public License.
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35 *
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36 * This exception applies only to the code released by The Free
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37 * Software Foundation under the name ServerHandler. If you copy code
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38 * from other sources under the General Public License into a copy of
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39 * ServerHandler, as the General Public License permits, the exception
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40 * does not apply to the code that you add in this way. To avoid
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41 * misleading anyone as to the status of such modified files, you must
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42 * delete this exception notice from them.
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43 *
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44 * If you write modifications of your own for ServerHandler, it is your
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45 * choice whether to permit this exception to apply to your modifications.
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46 * If you do not wish that, delete this exception notice.
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47 */
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48
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49 #include "fixlib.h"
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50 #include "server.h"
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51
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52 STATIC volatile enum t_bool read_pipe_timeout;
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53 STATIC pid_t server_master_pid = NOPROCESS;
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54
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55 tSCC* def_args[] =
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56 { (char *) NULL, (char *) NULL };
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57 STATIC t_pf_pair server_pair =
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58 { (FILE *) NULL, (FILE *) NULL };
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59 STATIC pid_t server_id = NULLPROCESS;
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60 /*
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61 * Arbitrary text that should not be found in the shell output.
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62 * It must be a single line and appear verbatim at the start of
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63 * the terminating output line.
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64 */
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65 tSCC z_done[] = "ShElL-OuTpUt-HaS-bEeN-cOmPlEtEd";
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66 tSCC* p_cur_dir = (char *) NULL;
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67
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68 /*
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69 * load_data
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70 *
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71 * Read data from a file pointer (a pipe to a process in this context)
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72 * until we either get EOF or we get a marker line back.
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73 * The read data are stored in a malloc-ed string that is truncated
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74 * to size at the end. Input is assumed to be an ASCII string.
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75 */
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76 static char *
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77 load_data (FILE* fp)
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78 {
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79 char *pz_text;
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80 size_t text_size;
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81 char *pz_scan;
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82 char z_line[1024];
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83 t_bool got_done = BOOL_FALSE;
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84
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85 text_size = sizeof (z_line) * 2;
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86 pz_scan = pz_text = XNEWVEC (char, text_size);
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87
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88 for (;;)
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89 {
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90 size_t used_ct;
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91
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92 alarm (10);
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93 read_pipe_timeout = BOOL_FALSE;
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94 if (fgets (z_line, sizeof (z_line), fp) == (char *) NULL)
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95 break;
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96
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97 if (strncmp (z_line, z_done, sizeof (z_done) - 1) == 0)
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98 {
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99 got_done = BOOL_TRUE;
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100 break;
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101 }
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102
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103 strcpy (pz_scan, z_line);
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104 pz_scan += strlen (z_line);
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105 used_ct = (size_t) (pz_scan - pz_text);
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106
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107 if (text_size - used_ct < sizeof (z_line))
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108 {
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109 size_t off = (size_t) (pz_scan - pz_text);
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110
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111 text_size += 4096;
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112 pz_text = XRESIZEVEC (char, pz_text, text_size);
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113 pz_scan = pz_text + off;
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114 }
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115 }
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116
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117 alarm (0);
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118 if (read_pipe_timeout || ! got_done)
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119 {
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120 free ((void *) pz_text);
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121 return (char *) NULL;
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122 }
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123
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124 while ((pz_scan > pz_text) && ISSPACE (pz_scan[-1]))
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125 pz_scan--;
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126 *pz_scan = NUL;
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127 return XRESIZEVEC (char, pz_text, strlen (pz_text) + 1);
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128 }
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129
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130
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131 /*
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132 * close_server
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133 *
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134 * Make certain the server process is dead, close the
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135 * pipes to it and from it, finally NULL out the file pointers
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136 */
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137 void
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138 close_server (void)
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139 {
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140 if ( (server_id != NULLPROCESS)
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141 && (server_master_pid == getpid ()))
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142 {
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143 kill ((pid_t) server_id, SIGKILL);
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144 server_id = NULLPROCESS;
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145 server_master_pid = NOPROCESS;
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146 fclose (server_pair.pf_read);
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147 fclose (server_pair.pf_write);
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148 server_pair.pf_read = server_pair.pf_write = (FILE *) NULL;
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149 }
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150 }
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151
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152 /*
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153 * sig_handler really only handles the timeout and pipe signals.
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154 * This ensures that we do not wait forever on a request
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155 * to our server, and also that if the server dies, we do not
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156 * die from a sigpipe problem.
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157 */
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158 static void
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159 sig_handler (int signo ATTRIBUTE_UNUSED)
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160 {
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161 #ifdef DEBUG
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162 /* FIXME: this is illegal to do in a signal handler. */
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163 fprintf (stderr,
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164 "fixincl ERROR: sig_handler: killed pid %ld due to %s\n",
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165 (long) server_id, signo == SIGPIPE ? "SIGPIPE" : "SIGALRM");
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166 #endif
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167 close_server ();
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168 read_pipe_timeout = BOOL_TRUE;
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169 }
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170
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171
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172 /*
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173 * server_setup Establish the signal handler for PIPE and ALARM.
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174 * Also establishes the current directory to give to the
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175 * server process at the start of every server command.
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176 */
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177 static void
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178 server_setup (void)
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179 {
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180 static int atexit_done = 0;
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181 char buff [MAXPATHLEN + 1];
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182
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183 if (atexit_done++ == 0)
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184 atexit (close_server);
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185 else
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186 fputs ("NOTE: server restarted\n", stderr);
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187
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188 server_master_pid = getpid ();
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189
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190 signal (SIGPIPE, sig_handler);
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191 signal (SIGALRM, sig_handler);
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192
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193 fputs ("trap : 1\n", server_pair.pf_write);
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194 fflush (server_pair.pf_write);
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195 getcwd (buff, MAXPATHLEN + 1);
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196 p_cur_dir = xstrdup (buff);
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197 }
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198
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199 /*
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200 * find_shell
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201 *
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202 * Locate a shell suitable for use. For various reasons
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203 * (like the use of "trap" in server_setup(), it must be a
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204 * Bourne-like shell.
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205 *
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206 * Most of the time, /bin/sh is preferred, but sometimes
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207 * it's quite broken (like on Ultrix). autoconf lets you
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208 * override with $CONFIG_SHELL, so we do the same.
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209 */
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210
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211 static const char *
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212 find_shell (void)
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213 {
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214 char * shell = getenv ("CONFIG_SHELL");
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215 if (shell)
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216 return shell;
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217
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218 return "/bin/sh";
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219 }
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220
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221
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222 /*
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223 * run_shell
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224 *
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225 * Run a shell command on the server. The command string
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226 * passed in is wrapped inside the sequence:
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227 *
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228 * cd <original directory>
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229 * <command string>
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230 * echo
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231 * echo <end-of-command-marker>
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232 *
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233 * This ensures that all commands start at a known place in
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234 * the directory structure, that any incomplete output lines
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235 * are completed and that our special marker sequence appears on
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236 * a line by itself. We have chosen a marker that is
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237 * excessively unlikely to be reproduced in normal output:
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238 *
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239 * "ShElL-OuTpUt-HaS-bEeN-cOmPlEtEd"
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240 */
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241 char *
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242 run_shell (const char* pz_cmd)
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243 {
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244 tSCC zNoServer[] = "Server not running, cannot run:\n%s\n\n";
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245 t_bool retry = BOOL_TRUE;
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246
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247 do_retry:
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248 /* IF the shell server process is not running yet,
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249 THEN try to start it. */
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250 if (server_id == NULLPROCESS)
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251 {
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252 def_args[0] = find_shell ();
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253
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254 server_id = proc2_fopen (&server_pair, def_args);
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255 if (server_id > 0)
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256 server_setup ();
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257 }
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258
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259 /* IF it is still not running, THEN return the nil string. */
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260 if (server_id <= 0)
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261 {
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262 fprintf (stderr, zNoServer, pz_cmd);
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263 return XCNEW (char);
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264 }
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265
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266 /* Make sure the process will pay attention to us, send the
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267 supplied command, and then have it output a special marker that
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268 we can find. */
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269 fprintf (server_pair.pf_write, "cd %s\n%s\n\necho\necho %s\n",
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270 p_cur_dir, pz_cmd, z_done);
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271 fflush (server_pair.pf_write);
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272
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273 /* IF the server died and we received a SIGPIPE,
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274 THEN return an empty string. */
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275 if (server_id == NULLPROCESS)
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276 {
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277 fprintf (stderr, zNoServer, pz_cmd);
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278 return XCNEW (char);
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279 }
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280
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281 /* Now try to read back all the data. If we fail due to either a
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282 sigpipe or sigalrm (timeout), we will return the nil string. */
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283 {
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284 char *pz = load_data (server_pair.pf_read);
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285
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286 if (pz == (char *) NULL)
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287 {
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288 close_server ();
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289
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290 if (retry)
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291 {
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292 retry = BOOL_FALSE;
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293 goto do_retry;
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294 }
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295
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296 fprintf (stderr, "CLOSING SHELL SERVER - command failure:\n\t%s\n",
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297 pz_cmd);
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298 pz = XCNEW (char);
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299 }
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300 #ifdef DEBUG
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301 fprintf( stderr, "run_shell command success: %s\n", pz );
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302 #endif
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303 return pz;
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304 }
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305 }
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