eval.c

   1 /* eval.c -- reading and evaluating commands. */
   2
   3 /* Copyright (C) 1996-2020 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 <signal.h>
  34
  35 #include "bashintl.h"
  36
  37 #include "shell.h"
  38 #include "parser.h"
  39 #include "flags.h"
  40 #include "trap.h"
  41
  42 #include "builtins/common.h"
  43
  44 #include "input.h"
  45 #include "execute_cmd.h"
  46
  47 #if defined (HISTORY)
  48 #  include "bashhist.h"
  49 #endif
  50
  51 static void send_pwd_to_eterm PARAMS((void));
  52 static sighandler alrm_catcher PARAMS((int));
  53
  54 /* Read and execute commands until EOF is reached.  This assumes that
  55    the input source has already been initialized. */
  56 int
  57 reader_loop ()
  58 {
  59   int our_indirection_level;
  60   COMMAND * volatile current_command;
  61
  62   USE_VAR(current_command);
  63
  64   current_command = (COMMAND *)NULL;
  65
  66   our_indirection_level = ++indirection_level;
  67
  68   if (just_one_command)
  69     reset_readahead_token ();
  70
  71   while (EOF_Reached == 0)
  72     {
  73       int code;
  74
  75       code = setjmp_nosigs (top_level);
  76
  77 #if defined (PROCESS_SUBSTITUTION)
  78       unlink_fifo_list ();
  79 #endif /* PROCESS_SUBSTITUTION */
  80
  81       /* XXX - why do we set this every time through the loop?  And why do
  82          it if SIGINT is trapped in an interactive shell? */
  83       if (interactive_shell && signal_is_ignored (SIGINT) == 0 && signal_is_trapped (SIGINT) == 0)
  84         set_signal_handler (SIGINT, sigint_sighandler);
  85
  86       if (code != NOT_JUMPED)
  87         {
  88           indirection_level = our_indirection_level;
  89
  90           switch (code)
  91             {
  92               /* Some kind of throw to top_level has occurred. */
  93             case FORCE_EOF:
  94             case ERREXIT:
  95             case EXITPROG:
  96               current_command = (COMMAND *)NULL;
  97               if (exit_immediately_on_error)
  98                 variable_context = 0;   /* not in a function */
  99               EOF_Reached = EOF;
 100               goto exec_done;
 101
 102             case DISCARD:
 103               /* Make sure the exit status is reset to a non-zero value, but
 104                  leave existing non-zero values (e.g., > 128 on signal)
 105                  alone. */
 106               if (last_command_exit_value == 0)
 107                 set_exit_status (EXECUTION_FAILURE);
 108               if (subshell_environment)
 109                 {
 110                   current_command = (COMMAND *)NULL;
 111                   EOF_Reached = EOF;
 112                   goto exec_done;
 113                 }
 114               /* Obstack free command elements, etc. */
 115               if (current_command)
 116                 {
 117                   dispose_command (current_command);
 118                   current_command = (COMMAND *)NULL;
 119                 }
 120
 121               restore_sigmask ();
 122               break;
 123
 124             default:
 125               command_error ("reader_loop", CMDERR_BADJUMP, code, 0);
 126             }
 127         }
 128
 129       executing = 0;
 130       if (temporary_env)
 131         dispose_used_env_vars ();
 132
 133 #if (defined (ultrix) && defined (mips)) || defined (C_ALLOCA)
 134       /* Attempt to reclaim memory allocated with alloca (). */
 135       (void) alloca (0);
 136 #endif
 137
 138       if (read_command () == 0)
 139         {
 140           if (interactive_shell == 0 && read_but_dont_execute)
 141             {
 142               set_exit_status (EXECUTION_SUCCESS);
 143               dispose_command (global_command);
 144               global_command = (COMMAND *)NULL;
 145             }
 146           else if (current_command = global_command)
 147             {
 148               global_command = (COMMAND *)NULL;
 149
 150               /* If the shell is interactive, expand and display $PS0 after reading a
 151                  command (possibly a list or pipeline) and before executing it. */
 152               if (interactive && ps0_prompt)
 153                 {
 154                   char *ps0_string;
 155
 156                   ps0_string = decode_prompt_string (ps0_prompt);
 157                   if (ps0_string && *ps0_string)
 158                     {
 159                       fprintf (stderr, "%s", ps0_string);
 160                       fflush (stderr);
 161                     }
 162                   free (ps0_string);
 163                 }
 164
 165               current_command_number++;
 166
 167               executing = 1;
 168               stdin_redir = 0;
 169
 170               execute_command (current_command);
 171
 172             exec_done:
 173               QUIT;
 174
 175               if (current_command)
 176                 {
 177                   dispose_command (current_command);
 178                   current_command = (COMMAND *)NULL;
 179                 }
 180             }
 181         }
 182       else
 183         {
 184           /* Parse error, maybe discard rest of stream if not interactive. */
 185           if (interactive == 0)
 186             EOF_Reached = EOF;
 187         }
 188       if (just_one_command)
 189         EOF_Reached = EOF;
 190     }
 191   indirection_level--;
 192   return (last_command_exit_value);
 193 }
 194
 195 /* Pretty print shell scripts */
 196 int
 197 pretty_print_loop ()
 198 {
 199   COMMAND *current_command;
 200   char *command_to_print;
 201   int code;
 202   int global_posix_mode, last_was_newline;
 203
 204   global_posix_mode = posixly_correct;
 205   last_was_newline = 0;
 206   while (EOF_Reached == 0)
 207     {
 208       code = setjmp_nosigs (top_level);
 209       if (code)
 210         return (EXECUTION_FAILURE);
 211       if (read_command() == 0)
 212         {
 213           current_command = global_command;
 214           global_command = 0;
 215           posixly_correct = 1;                  /* print posix-conformant */
 216           if (current_command && (command_to_print = make_command_string (current_command)))
 217             {
 218               printf ("%s\n", command_to_print);        /* for now */
 219               last_was_newline = 0;
 220             }
 221           else if (last_was_newline == 0)
 222             {
 223                printf ("\n");
 224                last_was_newline = 1;
 225             }
 226           posixly_correct = global_posix_mode;
 227           dispose_command (current_command);
 228         }
 229       else
 230         return (EXECUTION_FAILURE);
 231     }
 232
 233   return (EXECUTION_SUCCESS);
 234 }
 235
 236 static sighandler
 237 alrm_catcher(i)
 238      int i;
 239 {
 240   char *msg;
 241
 242   msg = _("\007timed out waiting for input: auto-logout\n");
 243   write (1, msg, strlen (msg));
 244
 245   bash_logout ();       /* run ~/.bash_logout if this is a login shell */
 246   jump_to_top_level (EXITPROG);
 247   SIGRETURN (0);
 248 }
 249
 250 /* Send an escape sequence to emacs term mode to tell it the
 251    current working directory. */
 252 static void
 253 send_pwd_to_eterm ()
 254 {
 255   char *pwd, *f;
 256
 257   f = 0;
 258   pwd = get_string_value ("PWD");
 259   if (pwd == 0)
 260     f = pwd = get_working_directory ("eterm");
 261   fprintf (stderr, "\032/%s\n", pwd);
 262   free (f);
 263 }
 264
 265 #if defined (ARRAY_VARS)
 266 /* Caller ensures that A has a non-zero number of elements */
 267 int
 268 execute_array_command (a, v)
 269      ARRAY *a;
 270      void *v;
 271 {
 272   char *tag;
 273   char **argv;
 274   int argc, i;
 275
 276   tag = (char *)v;
 277   argc = 0;
 278   argv = array_to_argv (a, &argc);
 279   for (i = 0; i < argc; i++)
 280     {
 281       if (argv[i] && argv[i][0])
 282         execute_variable_command (argv[i], tag);
 283     }
 284   strvec_dispose (argv);
 285   return 0;
 286 }
 287 #endif
 288
 289 static void
 290 execute_prompt_command ()
 291 {
 292   char *command_to_execute;
 293   SHELL_VAR *pcv;
 294 #if defined (ARRAY_VARS)
 295   ARRAY *pcmds;
 296 #endif
 297
 298   pcv = find_variable ("PROMPT_COMMAND");
 299   if (pcv  == 0 || var_isset (pcv) == 0 || invisible_p (pcv))
 300     return;
 301 #if defined (ARRAY_VARS)
 302   if (array_p (pcv))
 303     {
 304       if ((pcmds = array_cell (pcv)) && array_num_elements (pcmds) > 0)
 305         execute_array_command (pcmds, "PROMPT_COMMAND");
 306       return;
 307     }
 308   else if (assoc_p (pcv))
 309     return;     /* currently don't allow associative arrays here */
 310 #endif
 311
 312   command_to_execute = value_cell (pcv);
 313   if (command_to_execute && *command_to_execute)
 314     execute_variable_command (command_to_execute, "PROMPT_COMMAND");
 315 }
 316
 317 /* Call the YACC-generated parser and return the status of the parse.
 318    Input is read from the current input stream (bash_input).  yyparse
 319    leaves the parsed command in the global variable GLOBAL_COMMAND.
 320    This is where PROMPT_COMMAND is executed. */
 321 int
 322 parse_command ()
 323 {
 324   int r;
 325
 326   need_here_doc = 0;
 327   run_pending_traps ();
 328
 329   /* Allow the execution of a random command just before the printing
 330      of each primary prompt.  If the shell variable PROMPT_COMMAND
 331      is set then its value (array or string) is the command(s) to execute. */
 332   /* The tests are a combination of SHOULD_PROMPT() and prompt_again()
 333      from parse.y, which are the conditions under which the prompt is
 334      actually printed. */
 335   if (interactive && bash_input.type != st_string && parser_expanding_alias() == 0)
 336     {
 337 #if defined (READLINE)
 338       if (no_line_editing || (bash_input.type == st_stdin && parser_will_prompt ()))
 339 #endif
 340         execute_prompt_command ();
 341
 342       if (running_under_emacs == 2)
 343         send_pwd_to_eterm ();   /* Yuck */
 344     }
 345
 346   current_command_line_count = 0;
 347   r = yyparse ();
 348
 349   if (need_here_doc)
 350     gather_here_documents ();
 351
 352   return (r);
 353 }
 354
 355 /* Read and parse a command, returning the status of the parse.  The command
 356    is left in the globval variable GLOBAL_COMMAND for use by reader_loop.
 357    This is where the shell timeout code is executed. */
 358 int
 359 read_command ()
 360 {
 361   SHELL_VAR *tmout_var;
 362   int tmout_len, result;
 363   SigHandler *old_alrm;
 364
 365   set_current_prompt_level (1);
 366   global_command = (COMMAND *)NULL;
 367
 368   /* Only do timeouts if interactive. */
 369   tmout_var = (SHELL_VAR *)NULL;
 370   tmout_len = 0;
 371   old_alrm = (SigHandler *)NULL;
 372
 373   if (interactive)
 374     {
 375       tmout_var = find_variable ("TMOUT");
 376
 377       if (tmout_var && var_isset (tmout_var))
 378         {
 379           tmout_len = atoi (value_cell (tmout_var));
 380           if (tmout_len > 0)
 381             {
 382               old_alrm = set_signal_handler (SIGALRM, alrm_catcher);
 383               alarm (tmout_len);
 384             }
 385         }
 386     }
 387
 388   QUIT;
 389
 390   current_command_line_count = 0;
 391   result = parse_command ();
 392
 393   if (interactive && tmout_var && (tmout_len > 0))
 394     {
 395       alarm(0);
 396       set_signal_handler (SIGALRM, old_alrm);
 397     }
 398
 399   return (result);
 400 }