eval.c

   1 /* eval.c -- reading and evaluating commands. */
   2
   3 /* Copyright (C) 1996-2009 Free Software Foundation, Inc.
   4
   5    This file is part of GNU Bash, the Bourne Again SHell.
   6
   7    Bash is free software: you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation, either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    Bash 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 Bash.  If not, see <http://www.gnu.org/licenses/>.
  19 */
  20
  21 #include "config.h"
  22
  23 #if defined (HAVE_UNISTD_H)
  24 #  ifdef _MINIX
  25 #    include <sys/types.h>
  26 #  endif
  27 #  include <unistd.h>
  28 #endif
  29
  30 #include "bashansi.h"
  31 #include <stdio.h>
  32
  33 #include "bashintl.h"
  34
  35 #include "shell.h"
  36 #include "flags.h"
  37 #include "trap.h"
  38
  39 #include "builtins/common.h"
  40
  41 #include "input.h"
  42 #include "execute_cmd.h"
  43
  44 #if defined (HISTORY)
  45 #  include "bashhist.h"
  46 #endif
  47
  48 extern int EOF_reached;
  49 extern int indirection_level;
  50 extern int posixly_correct;
  51 extern int subshell_environment, running_under_emacs;
  52 extern int last_command_exit_value, stdin_redir;
  53 extern int need_here_doc;
  54 extern int current_command_number, current_command_line_count, line_number;
  55 extern int expand_aliases;
  56
  57 static void send_pwd_to_eterm __P((void));
  58 static sighandler alrm_catcher __P((int));
  59
  60 /* Read and execute commands until EOF is reached.  This assumes that
  61    the input source has already been initialized. */
  62 int
  63 reader_loop ()
  64 {
  65   int our_indirection_level;
  66   COMMAND * volatile current_command;
  67
  68   USE_VAR(current_command);
  69
  70   current_command = (COMMAND *)NULL;
  71
  72   our_indirection_level = ++indirection_level;
  73
  74   while (EOF_Reached == 0)
  75     {
  76       int code;
  77
  78       code = setjmp (top_level);
  79
  80 #if defined (PROCESS_SUBSTITUTION)
  81       unlink_fifo_list ();
  82 #endif /* PROCESS_SUBSTITUTION */
  83
  84       if (interactive_shell && signal_is_ignored (SIGINT) == 0)
  85         set_signal_handler (SIGINT, sigint_sighandler);
  86
  87       if (code != NOT_JUMPED)
  88         {
  89           indirection_level = our_indirection_level;
  90
  91           switch (code)
  92             {
  93               /* Some kind of throw to top_level has occured. */
  94             case FORCE_EOF:
  95             case ERREXIT:
  96             case EXITPROG:
  97               current_command = (COMMAND *)NULL;
  98               if (exit_immediately_on_error)
  99                 variable_context = 0;   /* not in a function */
 100               EOF_Reached = EOF;
 101               goto exec_done;
 102
 103             case DISCARD:
 104               /* Make sure the exit status is reset to a non-zero value, but
 105                  leave existing non-zero values (e.g., > 128 on signal)
 106                  alone. */
 107               if (last_command_exit_value == 0)
 108                 last_command_exit_value = EXECUTION_FAILURE;
 109               if (subshell_environment)
 110                 {
 111                   current_command = (COMMAND *)NULL;
 112                   EOF_Reached = EOF;
 113                   goto exec_done;
 114                 }
 115               /* Obstack free command elements, etc. */
 116               if (current_command)
 117                 {
 118                   dispose_command (current_command);
 119                   current_command = (COMMAND *)NULL;
 120                 }
 121               break;
 122
 123             default:
 124               command_error ("reader_loop", CMDERR_BADJUMP, code, 0);
 125             }
 126         }
 127
 128       executing = 0;
 129       if (temporary_env)
 130         dispose_used_env_vars ();
 131
 132 #if (defined (ultrix) && defined (mips)) || defined (C_ALLOCA)
 133       /* Attempt to reclaim memory allocated with alloca (). */
 134       (void) alloca (0);
 135 #endif
 136
 137       if (read_command () == 0)
 138         {
 139           if (interactive_shell == 0 && read_but_dont_execute)
 140             {
 141               last_command_exit_value = EXECUTION_SUCCESS;
 142               dispose_command (global_command);
 143               global_command = (COMMAND *)NULL;
 144             }
 145           else if (current_command = global_command)
 146             {
 147               global_command = (COMMAND *)NULL;
 148               current_command_number++;
 149
 150               executing = 1;
 151               stdin_redir = 0;
 152               execute_command (current_command);
 153
 154             exec_done:
 155               QUIT;
 156
 157               if (current_command)
 158                 {
 159                   dispose_command (current_command);
 160                   current_command = (COMMAND *)NULL;
 161                 }
 162             }
 163         }
 164       else
 165         {
 166           /* Parse error, maybe discard rest of stream if not interactive. */
 167           if (interactive == 0)
 168             EOF_Reached = EOF;
 169         }
 170       if (just_one_command)
 171         EOF_Reached = EOF;
 172     }
 173   indirection_level--;
 174   return (last_command_exit_value);
 175 }
 176
 177 static sighandler
 178 alrm_catcher(i)
 179      int i;
 180 {
 181   printf (_("\007timed out waiting for input: auto-logout\n"));
 182   fflush (stdout);
 183   bash_logout ();       /* run ~/.bash_logout if this is a login shell */
 184   jump_to_top_level (EXITPROG);
 185   SIGRETURN (0);
 186 }
 187
 188 /* Send an escape sequence to emacs term mode to tell it the
 189    current working directory. */
 190 static void
 191 send_pwd_to_eterm ()
 192 {
 193   char *pwd;
 194
 195   pwd = get_string_value ("PWD");
 196   if (pwd == 0)
 197     pwd = get_working_directory ("eterm");
 198   fprintf (stderr, "\032/%s\n", pwd);
 199 }
 200
 201 /* Call the YACC-generated parser and return the status of the parse.
 202    Input is read from the current input stream (bash_input).  yyparse
 203    leaves the parsed command in the global variable GLOBAL_COMMAND.
 204    This is where PROMPT_COMMAND is executed. */
 205 int
 206 parse_command ()
 207 {
 208   int r;
 209   char *command_to_execute;
 210
 211   need_here_doc = 0;
 212   run_pending_traps ();
 213
 214   /* Allow the execution of a random command just before the printing
 215      of each primary prompt.  If the shell variable PROMPT_COMMAND
 216      is set then the value of it is the command to execute. */
 217   if (interactive && bash_input.type != st_string)
 218     {
 219       command_to_execute = get_string_value ("PROMPT_COMMAND");
 220       if (command_to_execute)
 221         execute_variable_command (command_to_execute, "PROMPT_COMMAND");
 222
 223       if (running_under_emacs == 2)
 224         send_pwd_to_eterm ();   /* Yuck */
 225     }
 226
 227   current_command_line_count = 0;
 228   r = yyparse ();
 229
 230   if (need_here_doc)
 231     gather_here_documents ();
 232
 233   return (r);
 234 }
 235
 236 /* Read and parse a command, returning the status of the parse.  The command
 237    is left in the globval variable GLOBAL_COMMAND for use by reader_loop.
 238    This is where the shell timeout code is executed. */
 239 int
 240 read_command ()
 241 {
 242   SHELL_VAR *tmout_var;
 243   int tmout_len, result;
 244   SigHandler *old_alrm;
 245
 246   set_current_prompt_level (1);
 247   global_command = (COMMAND *)NULL;
 248
 249   /* Only do timeouts if interactive. */
 250   tmout_var = (SHELL_VAR *)NULL;
 251   tmout_len = 0;
 252   old_alrm = (SigHandler *)NULL;
 253
 254   if (interactive)
 255     {
 256       tmout_var = find_variable ("TMOUT");
 257
 258       if (tmout_var && var_isset (tmout_var))
 259         {
 260           tmout_len = atoi (value_cell (tmout_var));
 261           if (tmout_len > 0)
 262             {
 263               old_alrm = set_signal_handler (SIGALRM, alrm_catcher);
 264               alarm (tmout_len);
 265             }
 266         }
 267     }
 268
 269   QUIT;
 270
 271   current_command_line_count = 0;
 272   result = parse_command ();
 273
 274   if (interactive && tmout_var && (tmout_len > 0))
 275     {
 276       alarm(0);
 277       set_signal_handler (SIGALRM, old_alrm);
 278     }
 279
 280   return (result);
 281 }