new file mode 100644
--- /dev/null
+++ b/readline/tilde.c
@@ -0,0 +1,463 @@
+/* tilde.c -- Tilde expansion code (~/foo := $HOME/foo). */
+
+/* Copyright (C) 1988,1989 Free Software Foundation, Inc.
+
+   This file is part of GNU Readline, a library for reading lines
+   of text with interactive input and history editing.
+
+   Readline 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.
+
+   Readline 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 Readline; see the file COPYING.  If not, write to the Free
+   Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. */
+
+#if defined (HAVE_CONFIG_H)
+#  include <config.h>
+#endif
+
+#if defined (HAVE_UNISTD_H)
+#  include <unistd.h>
+#endif
+
+#if defined (HAVE_STRING_H)
+#  include <string.h>
+#else /* !HAVE_STRING_H */
+#  include <strings.h>
+#endif /* !HAVE_STRING_H */  
+
+#if defined (HAVE_STDLIB_H)
+#  include <stdlib.h>
+#else
+#  include "ansi_stdlib.h"
+#endif /* HAVE_STDLIB_H */
+
+#include <sys/types.h>
+#include <pwd.h>
+
+#include "tilde.h"
+
+#ifdef SHELL
+#include "shell.h"
+#endif
+
+#if !defined (HAVE_GETPW_DECLS)
+extern struct passwd *getpwuid (), *getpwnam ();
+#endif /* !HAVE_GETPW_DECLS */
+
+#if !defined (savestring)
+extern char *xmalloc ();
+#  ifndef strcpy
+extern char *strcpy ();
+#  endif
+#define savestring(x) strcpy (xmalloc (1 + strlen (x)), (x))
+#endif /* !savestring */
+
+#if !defined (NULL)
+#  if defined (__STDC__)
+#    define NULL ((void *) 0)
+#  else
+#    define NULL 0x0
+#  endif /* !__STDC__ */
+#endif /* !NULL */
+
+#if defined (TEST) || defined (STATIC_MALLOC)
+static char *xmalloc (), *xrealloc ();
+#else
+extern char *xmalloc (), *xrealloc ();
+#endif /* TEST || STATIC_MALLOC */
+
+/* The default value of tilde_additional_prefixes.  This is set to
+   whitespace preceding a tilde so that simple programs which do not
+   perform any word separation get desired behaviour. */
+static char *default_prefixes[] =
+  { " ~", "\t~", (char *)NULL };
+
+/* The default value of tilde_additional_suffixes.  This is set to
+   whitespace or newline so that simple programs which do not
+   perform any word separation get desired behaviour. */
+static char *default_suffixes[] =
+  { " ", "\n", (char *)NULL };
+
+/* If non-null, this contains the address of a function that the application
+   wants called before trying the standard tilde expansions.  The function
+   is called with the text sans tilde, and returns a malloc()'ed string
+   which is the expansion, or a NULL pointer if the expansion fails. */
+CPFunction *tilde_expansion_preexpansion_hook = (CPFunction *)NULL;
+
+/* If non-null, this contains the address of a function to call if the
+   standard meaning for expanding a tilde fails.  The function is called
+   with the text (sans tilde, as in "foo"), and returns a malloc()'ed string
+   which is the expansion, or a NULL pointer if there is no expansion. */
+CPFunction *tilde_expansion_failure_hook = (CPFunction *)NULL;
+
+/* When non-null, this is a NULL terminated array of strings which
+   are duplicates for a tilde prefix.  Bash uses this to expand
+   `=~' and `:~'. */
+char **tilde_additional_prefixes = default_prefixes;
+
+/* When non-null, this is a NULL terminated array of strings which match
+   the end of a username, instead of just "/".  Bash sets this to
+   `:' and `=~'. */
+char **tilde_additional_suffixes = default_suffixes;
+
+/* Find the start of a tilde expansion in STRING, and return the index of
+   the tilde which starts the expansion.  Place the length of the text
+   which identified this tilde starter in LEN, excluding the tilde itself. */
+static int
+tilde_find_prefix (string, len)
+     char *string;
+     int *len;
+{
+  register int i, j, string_len;
+  register char **prefixes = tilde_additional_prefixes;
+
+  string_len = strlen (string);
+  *len = 0;
+
+  if (*string == '\0' || *string == '~')
+    return (0);
+
+  if (prefixes)
+    {
+      for (i = 0; i < string_len; i++)
+	{
+	  for (j = 0; prefixes[j]; j++)
+	    {
+	      if (strncmp (string + i, prefixes[j], strlen (prefixes[j])) == 0)
+		{
+		  *len = strlen (prefixes[j]) - 1;
+		  return (i + *len);
+		}
+	    }
+	}
+    }
+  return (string_len);
+}
+
+/* Find the end of a tilde expansion in STRING, and return the index of
+   the character which ends the tilde definition.  */
+static int
+tilde_find_suffix (string)
+     char *string;
+{
+  register int i, j, string_len;
+  register char **suffixes;
+
+  suffixes = tilde_additional_suffixes;
+  string_len = strlen (string);
+
+  for (i = 0; i < string_len; i++)
+    {
+      if (string[i] == '/' /* || !string[i] */)
+	break;
+
+      for (j = 0; suffixes && suffixes[j]; j++)
+	{
+	  if (strncmp (string + i, suffixes[j], strlen (suffixes[j])) == 0)
+	    return (i);
+	}
+    }
+  return (i);
+}
+
+#if !defined (SHELL)
+static char *
+get_string_value (varname)
+     char *varname;
+{
+  return ((char *)getenv (varname));
+}
+#endif
+
+/* Return a new string which is the result of tilde expanding STRING. */
+char *
+tilde_expand (string)
+     char *string;
+{
+  char *result;
+  int result_size, result_index;
+
+  result_index = result_size = 0;
+  if (result = strchr (string, '~'))
+    result = xmalloc (result_size = (strlen (string) + 16));
+  else
+    result = xmalloc (result_size = strlen (string));
+
+  /* Scan through STRING expanding tildes as we come to them. */
+  while (1)
+    {
+      register int start, end;
+      char *tilde_word, *expansion;
+      int len;
+
+      /* Make START point to the tilde which starts the expansion. */
+      start = tilde_find_prefix (string, &len);
+
+      /* Copy the skipped text into the result. */
+      if ((result_index + start + 1) > result_size)
+	result = xrealloc (result, 1 + (result_size += (start + 20)));
+
+      strncpy (result + result_index, string, start);
+      result_index += start;
+
+      /* Advance STRING to the starting tilde. */
+      string += start;
+
+      /* Make END be the index of one after the last character of the
+	 username. */
+      end = tilde_find_suffix (string);
+
+      /* If both START and END are zero, we are all done. */
+      if (!start && !end)
+	break;
+
+      /* Expand the entire tilde word, and copy it into RESULT. */
+      tilde_word = xmalloc (1 + end);
+      strncpy (tilde_word, string, end);
+      tilde_word[end] = '\0';
+      string += end;
+
+      expansion = tilde_expand_word (tilde_word);
+      free (tilde_word);
+
+      len = strlen (expansion);
+      if ((result_index + len + 1) > result_size)
+	result = xrealloc (result, 1 + (result_size += (len + 20)));
+
+      strcpy (result + result_index, expansion);
+      result_index += len;
+      free (expansion);
+    }
+
+  result[result_index] = '\0';
+
+  return (result);
+}
+
+/* Take FNAME and return the tilde prefix we want expanded.  If LENP is
+   non-null, the index of the end of the prefix into FNAME is returned in
+   the location it points to. */
+static char *
+isolate_tilde_prefix (fname, lenp)
+     char *fname;
+     int *lenp;
+{
+  char *ret;
+  int i;
+
+  ret = xmalloc (strlen (fname));
+  for (i = 1; fname[i] && fname[i] != '/'; i++)
+    ret[i - 1] = fname[i];
+  ret[i - 1] = '\0';
+  if (lenp)
+    *lenp = i;
+  return ret;
+}
+
+/* Return a string that is PREFIX concatenated with SUFFIX starting at
+   SUFFIND. */
+static char *
+glue_prefix_and_suffix (prefix, suffix, suffind)
+     char *prefix, *suffix;
+     int suffind;
+{
+  char *ret;
+  int plen, slen;
+
+  plen = (prefix && *prefix) ? strlen (prefix) : 0;
+  slen = strlen (suffix + suffind);
+  ret = xmalloc (plen + slen + 1);
+  if (prefix && *prefix)
+    strcpy (ret, prefix);
+  strcpy (ret + plen, suffix + suffind);
+  return ret;
+}
+
+static char *
+get_home_dir ()
+{
+  char *home_dir;
+
+#ifdef SHELL
+  home_dir = (char *)NULL;
+  if (current_user.home_dir == 0)
+    get_current_user_info ();
+  home_dir = current_user.home_dir;
+#else
+  struct passwd *entry;
+
+  home_dir = (char *)NULL;
+  entry = getpwuid (getuid ());
+  if (entry)
+    home_dir = entry->pw_dir;
+#endif
+  return (home_dir);
+}
+
+/* Do the work of tilde expansion on FILENAME.  FILENAME starts with a
+   tilde.  If there is no expansion, call tilde_expansion_failure_hook.
+   This always returns a newly-allocated string, never static storage. */
+char *
+tilde_expand_word (filename)
+     char *filename;
+{
+  char *dirname, *expansion, *username;
+  int user_len;
+  struct passwd *user_entry;
+
+  if (filename == 0)
+    return ((char *)NULL);
+
+  if (*filename != '~')
+    return (savestring (filename));
+
+  /* A leading `~/' or a bare `~' is *always* translated to the value of
+     $HOME or the home directory of the current user, regardless of any
+     preexpansion hook. */
+  if (filename[1] == '\0' || filename[1] == '/')
+    {
+      /* Prefix $HOME to the rest of the string. */
+      expansion = get_string_value ("HOME");
+
+      /* If there is no HOME variable, look up the directory in
+	 the password database. */
+      if (expansion == 0)
+	expansion = get_home_dir ();
+
+      return (glue_prefix_and_suffix (expansion, filename, 1));
+    }
+
+  username = isolate_tilde_prefix (filename, &user_len);
+
+  if (tilde_expansion_preexpansion_hook)
+    {
+      expansion = (*tilde_expansion_preexpansion_hook) (username);
+      if (expansion)
+	{
+	  dirname = glue_prefix_and_suffix (expansion, filename, user_len);
+	  free (username);
+	  free (expansion);
+	  return (dirname);
+	}
+    }
+
+  /* No preexpansion hook, or the preexpansion hook failed.  Look in the
+     password database. */
+  dirname = (char *)NULL;
+  user_entry = getpwnam (username);
+  if (user_entry == 0)
+    {
+      /* If the calling program has a special syntax for expanding tildes,
+	 and we couldn't find a standard expansion, then let them try. */
+      if (tilde_expansion_failure_hook)
+	{
+	  expansion = (*tilde_expansion_failure_hook) (username);
+	  if (expansion)
+	    {
+	      dirname = glue_prefix_and_suffix (expansion, filename, user_len);
+	      free (expansion);
+	    }
+	}
+      free (username);
+      /* If we don't have a failure hook, or if the failure hook did not
+	 expand the tilde, return a copy of what we were passed. */
+      if (dirname == 0)
+	dirname = savestring (filename);
+    }
+  else
+    {
+      free (username);
+      dirname = glue_prefix_and_suffix (user_entry->pw_dir, filename, user_len);
+    }
+
+  endpwent ();
+  return (dirname);
+}
+
+
+#if defined (TEST)
+#undef NULL
+#include <stdio.h>
+
+main (argc, argv)
+     int argc;
+     char **argv;
+{
+  char *result, line[512];
+  int done = 0;
+
+  while (!done)
+    {
+      printf ("~expand: ");
+      fflush (stdout);
+
+      if (!gets (line))
+	strcpy (line, "done");
+
+      if ((strcmp (line, "done") == 0) ||
+	  (strcmp (line, "quit") == 0) ||
+	  (strcmp (line, "exit") == 0))
+	{
+	  done = 1;
+	  break;
+	}
+
+      result = tilde_expand (line);
+      printf ("  --> %s\n", result);
+      free (result);
+    }
+  exit (0);
+}
+
+static void memory_error_and_abort ();
+
+static char *
+xmalloc (bytes)
+     int bytes;
+{
+  char *temp = (char *)malloc (bytes);
+
+  if (!temp)
+    memory_error_and_abort ();
+  return (temp);
+}
+
+static char *
+xrealloc (pointer, bytes)
+     char *pointer;
+     int bytes;
+{
+  char *temp;
+
+  if (!pointer)
+    temp = (char *)malloc (bytes);
+  else
+    temp = (char *)realloc (pointer, bytes);
+
+  if (!temp)
+    memory_error_and_abort ();
+
+  return (temp);
+}
+
+static void
+memory_error_and_abort ()
+{
+  fprintf (stderr, "readline: out of virtual memory\n");
+  abort ();
+}
+
+/*
+ * Local variables:
+ * compile-command: "gcc -g -DTEST -o tilde tilde.c"
+ * end:
+ */
+#endif /* TEST */