This file is read.def, from which is created read.c.
It implements the builtin "read" 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 2, 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, 59 Temple Place, Suite 330, Boston, MA 02111 USA.

$PRODUCES read.c

$BUILTIN read
$FUNCTION read_builtin
$SHORT_DOC read [-ers] [-t timeout] [-p prompt] [-a array] [-n nchars] [-d delim] [name ...]
One line is read from the standard input, and the first word is
assigned to the first NAME, the second word to the second NAME, and so
on, with leftover words assigned to the last NAME.  Only the characters
found in $IFS are recognized as word delimiters.  If no NAMEs are supplied,
the line read is stored in the REPLY variable.  If the -r option is given,
this signifies `raw' input, and backslash escaping is disabled.  The
-d option causes read to continue until the first character of DELIM is
read, rather than newline.  If the `-p' option is supplied, the string
PROMPT is output without a trailing newline before attempting to read.
If -a is supplied, the words read are assigned to sequential indices of
ARRAY, starting at zero.  If -e is supplied and the shell is interactive,
readline is used to obtain the line.  If -n is supplied with a non-zero
NCHARS argument, read returns after NCHARS characters have been read.
The -s option causes input coming from a terminal to not be echoed.

The -t option causes read to time out and return failure if a complete line
of input is not read within TIMEOUT seconds.  The return code is zero,
unless end-of-file is encountered or read times out.
$END

#include <config.h>

#include "bashtypes.h"
#include "posixstat.h"

#include <stdio.h>

#if defined (HAVE_UNISTD_H)
#  include <unistd.h>
#endif

#include <signal.h>
#include <errno.h>

#ifdef __CYGWIN__
#  include <fcntl.h>
#  include <io.h>
#endif

#include "../shell.h"
#include "common.h"
#include "bashgetopt.h"

#include <shtty.h>

#if defined (READLINE)
#include "../bashline.h"
#include <readline/readline.h>
#endif

#if !defined(errno)
extern int errno;
#endif

#define issep(c)	(strchr (ifs_chars, (c)))

extern int interrupt_immediately;

#if defined (READLINE)
static char *edit_line ();
static void set_eol_delim ();
static void reset_eol_delim ();
#endif
static SHELL_VAR *bind_read_variable ();

static procenv_t alrmbuf;
static SigHandler *old_alrm;
static int delim;

static sighandler
sigalrm (s)
     int s;
{
  longjmp (alrmbuf, 1);
}

static void
reset_alarm ()
{
  set_signal_handler (SIGALRM, old_alrm);
  alarm (0);
}

/* Read the value of the shell variables whose names follow.
   The reading is done from the current input stream, whatever
   that may be.  Successive words of the input line are assigned
   to the variables mentioned in LIST.  The last variable in LIST
   gets the remainder of the words on the line.  If no variables
   are mentioned in LIST, then the default variable is $REPLY. */
int
read_builtin (list)
     WORD_LIST *list;
{
  register char *varname;
  int size, i, pass_next, saw_escape, eof, opt, retval, code;
  int input_is_tty, input_is_pipe, unbuffered_read;
  int raw, edit, tmout, nchars, silent;
  long timeoutval, ncharsval;
  char c;
  char *input_string, *orig_input_string, *ifs_chars, *prompt, *arrayname;
  char *e, *t, *t1;
  struct stat tsb;
  SHELL_VAR *var;
#if defined (ARRAY_VARS)
  WORD_LIST *alist;
#endif
#if defined (READLINE)
  char *rlbuf;
  int rlind;
#endif

  i = 0;		/* Index into the string that we are reading. */
  raw = edit = 0;	/* Not reading raw input by default. */
  silent = 0;
  arrayname = prompt = (char *)NULL;

#if defined (READLINE)
  rlbuf = (char *)0;
  rlind = 0;
#endif

  tmout = -1;		/* no timeout */
  nchars = input_is_tty = input_is_pipe = unbuffered_read = 0;
  delim = '\n';		/* read until newline */

  reset_internal_getopt ();
  while ((opt = internal_getopt (list, "erp:a:d:t:n:s")) != -1)
    {
      switch (opt)
	{
	case 'r':
	  raw = 1;
	  break;
	case 'p':
	  prompt = list_optarg;
	  break;
	case 's':
	  silent = 1;
	  break;
	case 'e':
#if defined (READLINE)
	  edit = 1;
#endif
	  break;
#if defined (ARRAY_VARS)
	case 'a':
	  arrayname = list_optarg;
	  break;
#endif
	case 't':
	  code = legal_number (list_optarg, &timeoutval);
	  if (code == 0 || timeoutval < 0)
	    {
	      builtin_error ("%s: invalid timeout specification", list_optarg);
	      return (EXECUTION_FAILURE);
	    }
	  else
	    tmout = timeoutval;
	  break;
	case 'n':
	  code = legal_number (list_optarg, &ncharsval);
	  if (code == 0 || ncharsval < 0)
	    {
	      builtin_error ("%s: invalid number specification", list_optarg);
	      return (EXECUTION_FAILURE);
	    }
	  else
	    nchars = ncharsval;
	  break;
	case 'd':
	  delim = *list_optarg;
	  break;
	default:
	  builtin_usage ();
	  return (EX_USAGE);
	}
    }
  list = loptend;

  /* `read -t 0 var' returns failure immediately. */
  if (tmout == 0)
    return (EXECUTION_FAILURE);

  /* IF IFS is unset, we use the default of " \t\n". */
  var = find_variable ("IFS");
  ifs_chars = var ? value_cell (var) : " \t\n";
  if (ifs_chars == 0)		/* XXX */
    ifs_chars = "";		/* XXX */

  input_string = xmalloc (size = 128);

  begin_unwind_frame ("read_builtin");
#if defined (READLINE)
  add_unwind_protect (xfree, rlbuf);
#endif

  input_is_tty = isatty (0);
  if (input_is_tty == 0)
#ifndef __CYGWIN__
    input_is_pipe = (lseek (0, 0L, SEEK_CUR) < 0) && (errno == ESPIPE);
#else
    input_is_pipe = 1;
#endif

  /* If the -p, -e or -s flags were given, but input is not coming from the
     terminal, turn them off. */
  if ((prompt || edit || silent) && input_is_tty == 0)
    {
      prompt = (char *)NULL;
      edit = silent = 0;
    }

  if (prompt && edit == 0)
    {
      fprintf (stderr, "%s", prompt);
      fflush (stderr);
    }

  pass_next = 0;	/* Non-zero signifies last char was backslash. */
  saw_escape = 0;	/* Non-zero signifies that we saw an escape char */

  if (tmout > 0)
    {
      /* Turn off the timeout if stdin is a regular file (e.g. from
	 input redirection). */
      if ((fstat (0, &tsb) < 0) || S_ISREG (tsb.st_mode))
	tmout = -1;
    }

  if (tmout > 0)
    {
      code = setjmp (alrmbuf);
      if (code)
	{
	  run_unwind_frame ("read_builtin");
	  return (EXECUTION_FAILURE);
	}
      old_alrm = set_signal_handler (SIGALRM, sigalrm);
      add_unwind_protect (reset_alarm, (char *)NULL);
      alarm (tmout);
    }

  /* If we've been asked to read only NCHARS chars, or we're using some
     character other than newline to terminate the line, do the right
     thing to readline or the tty. */
  if (nchars > 0 || delim != '\n')
    {
#if defined (READLINE)
      if (edit)
	{
	  if (nchars > 0)
	    {
	      unwind_protect_int (rl_num_chars_to_read);
	      rl_num_chars_to_read = nchars;
	    }
	  if (delim != '\n')
	    {
	      set_eol_delim (delim);
	      add_unwind_protect (reset_eol_delim, (char *)NULL);
	    }
	}
      else
#endif
      if (input_is_tty)
	{
	  ttsave ();
	  if (silent)
	    ttcbreak ();
	  else
	    ttonechar ();
	  add_unwind_protect ((Function *)ttrestore, (char *)NULL);
	}
    }
  else if (silent)	/* turn off echo but leave term in canonical mode */
    {
      ttsave ();
      ttnoecho ();
      add_unwind_protect ((Function *)ttrestore, (char *)NULL);
    }

  /* This *must* be the top unwind-protect on the stack, so the manipulation
     of the unwind-protect stack after the realloc() works right. */
  add_unwind_protect (xfree, input_string);
  interrupt_immediately++;

  unbuffered_read = (nchars > 0) || (delim != '\n') || input_is_pipe;

#if defined (__CYGWIN__) && defined (O_TEXT)
  setmode (0, O_TEXT);
#endif

  for (eof = 0;;)
    {
#if defined (READLINE)
      if (edit)
	{
	  if (rlbuf && rlbuf[rlind] == '\0')
	    {
	      xfree (rlbuf);
	      rlbuf = (char *)0;
	    }
	  if (rlbuf == 0)
	    {
	      rlbuf = edit_line (prompt ? prompt : "");
	      rlind = 0;
	    }
	  if (rlbuf == 0)
	    {
	      eof = 1;
	      break;
	    }
	  c = rlbuf[rlind++];
	}
      else
	{
#endif

      if (unbuffered_read)
	retval = zread (0, &c, 1);
      else
	retval = zreadc (0, &c);

      if (retval <= 0)
	{
	  eof = 1;
	  break;
	}

#if defined (READLINE)
	}
#endif

      if (i + 2 >= size)
	{
	  input_string = xrealloc (input_string, size += 128);
	  remove_unwind_protect ();
	  add_unwind_protect (xfree, input_string);
	}

      /* If the next character is to be accepted verbatim, a backslash
	 newline pair still disappears from the input. */
      if (pass_next)
	{
	  if (c == '\n')
	    i--;		/* back up over the CTLESC */
	  else
	    input_string[i++] = c;
	  pass_next = 0;
	  continue;
	}

      if (c == '\\' && raw == 0)
	{
	  pass_next++;
	  saw_escape++;
	  input_string[i++] = CTLESC;
	  continue;
	}

      if (c == delim)
	break;

      if (c == CTLESC || c == CTLNUL)
	{
	  saw_escape++;
	  input_string[i++] = CTLESC;
	}

      input_string[i++] = c;

      if (nchars > 0 && i >= nchars)
	break;
    }
  input_string[i] = '\0';

  if (tmout > 0)
    reset_alarm ();

  if (nchars > 0 || delim != '\n')
    {
#if defined (READLINE)
      if (edit)
	{
	  if (nchars > 0)
	    rl_num_chars_to_read = 0;
	  if (delim != '\n')
	    reset_eol_delim ();
	}
      else
#endif
      if (input_is_tty)
	ttrestore ();
    }
  else if (silent)
    ttrestore ();

  if (unbuffered_read == 0)
    zsyncfd (0);

  interrupt_immediately--;
  discard_unwind_frame ("read_builtin");

  retval = eof ? EXECUTION_FAILURE : EXECUTION_SUCCESS;

#if defined (ARRAY_VARS)
  /* If -a was given, take the string read, break it into a list of words,
     an assign them to `arrayname' in turn. */
  if (arrayname)
    {
      var = find_variable (arrayname);
      if (var == 0)
	var = make_new_array_variable (arrayname);
      else if (array_p (var) == 0)
	var = convert_var_to_array (var);

      empty_array (array_cell (var));

      alist = list_string (input_string, ifs_chars, 0);
      if (alist)
	{
	  assign_array_var_from_word_list (var, alist);
	  dispose_words (alist);
	}
      xfree (input_string);
      return (retval);
    }
#endif /* ARRAY_VARS */ 

  /* If there are no variables, save the text of the line read to the
     variable $REPLY.  ksh93 strips leading and trailing IFS whitespace,
     so that `read x ; echo "$x"' and `read ; echo "$REPLY"' behave the
     same way, but I believe that the difference in behaviors is useful
     enough to not do it.  Without the bash behavior, there is no way
     to read a line completely without interpretation or modification
     unless you mess with $IFS (e.g., setting it to the empty string).
     If you disagree, change the occurrences of `#if 0' to `#if 1' below. */
  if (list == 0)
    {
#if 0
      orig_input_string = input_string;
      for (t = input_string; ifs_chars && *ifs_chars && spctabnl(*t) && issep(*t); t++)
	;
      input_string = t;
      input_string = strip_trailing_ifs_whitespace (input_string, ifs_chars, saw_escape);
#endif

      if (saw_escape)
	{
	  t = dequote_string (input_string);
	  var = bind_variable ("REPLY", t);
	  free (t);
	}
      else
	var = bind_variable ("REPLY", input_string);
      VUNSETATTR (var, att_invisible);

      free (input_string);
      return (retval);
    }

  /* This code implements the Posix.2 spec for splitting the words
     read and assigning them to variables. */
  orig_input_string = input_string;

  /* Remove IFS white space at the beginning of the input string.  If
     $IFS is null, no field splitting is performed. */
  for (t = input_string; ifs_chars && *ifs_chars && spctabnl(*t) && issep(*t); t++)
    ;
  input_string = t;

  for (; list->next; list = list->next)
    {
      varname = list->word->word;
#if defined (ARRAY_VARS)
      if (legal_identifier (varname) == 0 && valid_array_reference (varname) == 0)
#else
      if (legal_identifier (varname) == 0)
#endif
	{
	  builtin_error ("`%s': not a valid identifier", varname);
	  free (orig_input_string);
	  return (EXECUTION_FAILURE);
	}

      /* If there are more variables than words read from the input,
	 the remaining variables are set to the empty string. */
      if (*input_string)
	{
	  /* This call updates INPUT_STRING. */
	  t = get_word_from_string (&input_string, ifs_chars, &e);
	  if (t)
	    *e = '\0';
	  /* Don't bother to remove the CTLESC unless we added one
	     somewhere while reading the string. */
	  if (t && saw_escape)
	    {
	      t1 = dequote_string (t);
	      var = bind_read_variable (varname, t1);
	      free (t1);
	    }
	  else
	    var = bind_read_variable (varname, t);
	}
      else
	{
	  t = (char *)0;
	  var = bind_read_variable (varname, "");
	}

      FREE (t);
      if (var == 0)
	{
	  free (orig_input_string);
	  return (EXECUTION_FAILURE);
	}

      stupidly_hack_special_variables (varname);
      VUNSETATTR (var, att_invisible);
    }

  /* Now assign the rest of the line to the last variable argument. */
#if defined (ARRAY_VARS)
  if (legal_identifier (list->word->word) == 0 && valid_array_reference (list->word->word) == 0)
#else
  if (legal_identifier (list->word->word) == 0)
#endif
    {
      builtin_error ("`%s': not a valid identifier", list->word->word);
      free (orig_input_string);
      return (EXECUTION_FAILURE);
    }

  /* This has to be done this way rather than using string_list
     and list_string because Posix.2 says that the last variable gets the
     remaining words and their intervening separators. */
  input_string = strip_trailing_ifs_whitespace (input_string, ifs_chars, saw_escape);

  if (saw_escape)
    {
      t = dequote_string (input_string);
      var = bind_read_variable (list->word->word, t);
      free (t);
    }
  else
    var = bind_read_variable (list->word->word, input_string);
  stupidly_hack_special_variables (list->word->word);
  if (var)
    VUNSETATTR (var, att_invisible);
  free (orig_input_string);

  return (retval);
}

static SHELL_VAR *
bind_read_variable (name, value)
     char *name, *value;
{
#if defined (ARRAY_VARS)
  if (valid_array_reference (name) == 0)
    {
#if 0
      if (legal_identifier (name) == 0)
	{
	  builtin_error ("`%s': not a valid identifier", name);
	  return ((SHELL_VAR *)NULL);
	}
#endif
      return (bind_variable (name, value));
    }
  else
    return (do_array_element_assignment (name, value));
#else
  return bind_variable (name, value);
#endif
}

#if defined (READLINE)
static char *
edit_line (p)
     char *p;
{
  char *ret;
  int len;

  if (!bash_readline_initialized)
    initialize_readline ();
  ret = readline (p);
  if (ret == 0)
    return ret;
  len = strlen (ret);
  ret = xrealloc (ret, len + 2);
  ret[len++] = delim;
  ret[len] = '\0';
  return ret;
}

static int old_delim_ctype;
static Function *old_delim_func;
static int old_newline_ctype;
static Function *old_newline_func;

static int delim_char;

static void
set_eol_delim (c)
     int c;
{
  Keymap cmap;

  if (bash_readline_initialized == 0)
    initialize_readline ();
  cmap = rl_get_keymap ();

  /* Change newline to self-insert */
  old_newline_ctype = cmap[RETURN].type;
  old_newline_func =  cmap[RETURN].function;
  cmap[RETURN].type = ISFUNC;
  cmap[RETURN].function = rl_insert;

  /* Bind the delimiter character to accept-line. */
  old_delim_ctype = cmap[c].type;
  old_delim_func = cmap[c].function;
  cmap[c].type = ISFUNC;
  cmap[c].function = rl_newline;

  delim_char = c;
}

static void
reset_eol_delim (c)
     int c;
{
  Keymap cmap;

  cmap = rl_get_keymap ();

  cmap[RETURN].type = old_newline_ctype;
  cmap[RETURN].function = old_newline_func;

  cmap[delim_char].type = old_delim_ctype;
  cmap[delim_char].function = old_delim_func;
}
#endif