This file is source.def, from which is created source.c.
It implements the builtins "." and  "source" in Bash.

Copyright (C) 1987, 1989, 1991 Free Software Foundation, Inc.

This file is part of GNU Bash, the Bourne Again SHell.

Bash is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free
Software Foundation; either version 1, or (at your option) any later
version.

Bash is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
for more details.

You should have received a copy of the GNU General Public License along
with Bash; see the file COPYING.  If not, write to the Free Software
Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.

$PRODUCES source.c

$BUILTIN source
$FUNCTION source_builtin
$SHORT_DOC source filename
Read and execute commands from FILENAME and return.  The pathnames
in $PATH are used to find the directory containing FILENAME.
$END
$BUILTIN .
$DOCNAME dot
$FUNCTION source_builtin
$SHORT_DOC . filename
Read and execute commands from FILENAME and return.  The pathnames
in $PATH are used to find the directory containing FILENAME.
$END
/* source.c - Implements the `.' and `source' builtins. */

#include <sys/types.h>
#include <sys/file.h>
#include <errno.h>

#if defined (HAVE_STRING_H)
#  include <string.h>
#else /* !HAVE_STRING_H */
#  include <strings.h>
#endif /* !HAVE_STRING_H */

#include "../shell.h"
#include "../posixstat.h"
#include "../filecntl.h"
#include "../execute_cmd.h"

/* Not all systems declare ERRNO in errno.h... and some systems #define it! */
#if !defined (errno)
extern int errno;
#endif /* !errno */

/* Variables used here but defined in other files. */
extern int return_catch_flag, return_catch_value;
extern jmp_buf return_catch;
extern int posixly_correct;
extern int interactive, interactive_shell, last_command_exit_value;

/* How many `levels' of sourced files we have. */
int sourcelevel = 0;

/* If this . script is supplied arguments, we save the dollar vars and
   replace them with the script arguments for the duration of the script's
   execution.  If the script does not change the dollar vars, we restore
   what we saved.  If the dollar vars are changed in the script, we leave
   the new values alone and free the saved values. */
static void
maybe_pop_dollar_vars ()
{
  if (dollar_vars_changed ())
    {
      dispose_saved_dollar_vars ();
      set_dollar_vars_unchanged ();
    }
  else
    pop_dollar_vars ();
}

/* Read and execute commands from the file passed as argument.  Guess what.
   This cannot be done in a subshell, since things like variable assignments
   take place in there.  So, I open the file, place it into a large string,
   close the file, and then execute the string. */
source_builtin (list)
     WORD_LIST *list;
{
  int result, return_val;

  /* Assume the best. */
  result = EXECUTION_SUCCESS;

  if (list)
    {
      char *string, *filename;
      struct stat finfo;
      int fd, tt;

      filename = find_path_file (list->word->word);
      if (!filename)
	filename = savestring (list->word->word);

      if (((fd = open (filename, O_RDONLY)) < 0) || (fstat (fd, &finfo) < 0))
	goto file_error_exit;

      string = (char *)xmalloc (1 + (int)finfo.st_size);
      tt = read (fd, string, finfo.st_size);
      string[finfo.st_size] = '\0';

      /* Close the open file, preserving the state of errno. */
      { int temp = errno; close (fd); errno = temp; }

      if (tt != finfo.st_size)
	{
	  free (string);

	file_error_exit:
	  file_error (filename);
	  free (filename);

	  /* POSIX shells exit if non-interactive and file error. */
	  if (posixly_correct && !interactive_shell)
	    {
	      last_command_exit_value = 1;
	      longjmp (top_level, EXITPROG);
	    }

	  return (EXECUTION_FAILURE);
	}

      if (tt > 80)
	tt = 80;

      if (check_binary_file ((unsigned char *)string, tt))
	{
	  free (string);
	  builtin_error ("%s: cannot execute binary file", filename);
	  free (filename);
	  return (EX_BINARY_FILE);
	}

      begin_unwind_frame ("File Sourcing");

      if (list->next)
	{
	  push_dollar_vars ();
	  add_unwind_protect ((Function *)maybe_pop_dollar_vars, (char *)NULL);
	  remember_args (list->next, 1);
	}

      unwind_protect_int (return_catch_flag);
      unwind_protect_jmp_buf (return_catch);
      unwind_protect_int (interactive);
      unwind_protect_int (sourcelevel);
      add_unwind_protect ((Function *)xfree, filename);
      interactive = 0;
      sourcelevel++;

      set_dollar_vars_unchanged ();

      return_catch_flag++;
      return_val = setjmp (return_catch);

      if (return_val)
	parse_and_execute_cleanup ();
      else
	result = parse_and_execute (string, filename, -1);

      run_unwind_frame ("File Sourcing");

      /* If RETURN_VAL is non-zero, then we return the value given
	 to return_builtin (), since that is how we got here. */
      if (return_val)
	result = return_catch_value;
    }
  else
    {
      builtin_error ("filename argument required");
      result = EXECUTION_FAILURE;
    }
  return (result);
}