Initial revision

1 files changed, 196 insertions, 0 deletions

diff --git a/lib/getusershell.c b/lib/getusershell.c
new file mode 100644
index 000000000..6e2e0c105
--- /dev/null
+++ b/lib/getusershell.c
@@ -0,0 +1,196 @@
+/* getusershell.c -- Return names of valid user shells.
+   Copyright (C) 1991 Free Software Foundation, Inc.
+
+   This program 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.
+
+   This program 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 this program; if not, write to the Free Software
+   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.  */
+
+/* Written by David MacKenzie <djm@gnu.ai.mit.edu> */
+
+#ifndef SHELLS_FILE
+/* File containing a list of nonrestricted shells, one per line. */
+#define SHELLS_FILE "/etc/shells"
+#endif
+
+#include <stdio.h>
+#include <ctype.h>
+
+#ifdef STDC_HEADERS
+#include <stdlib.h>
+#else
+char *malloc ();
+char *realloc ();
+#endif
+
+static int readname ();
+
+/* List of shells to use if the shells file is missing. */
+static char *default_shells[] =
+{
+  "/bin/sh", "/bin/csh", "/usr/bin/sh", "/usr/bin/csh", NULL
+};
+
+/* Index of the next shell in `default_shells' to return.
+   0 means we are not using `default_shells'. */
+static int default_index = 0;
+
+/* Input stream from the shells file. */
+static FILE *shellstream = NULL;
+
+/* Line of input from the shells file. */
+static char *line = NULL;
+
+/* Number of bytes allocated for `line'. */
+static int line_size = 0;
+
+/* Return an entry from the shells file, ignoring comment lines.
+   Return NULL if there are no more entries.  */
+
+char *
+getusershell ()
+{
+  if (default_index > 0)
+    {
+      if (default_shells[default_index])
+	/* Not at the end of the list yet.  */
+	return default_shells[default_index++];
+      return NULL;
+    }
+
+  if (shellstream == NULL)
+    {
+      shellstream = fopen (SHELLS_FILE, "r");
+      if (shellstream == NULL)
+	{
+	  /* No shells file.  Use the default list.  */
+	  default_index = 1;
+	  return default_shells[0];
+	}
+    }
+
+  while (readname (&line, &line_size, shellstream))
+    {
+      if (*line != '#')
+	return line;
+    }
+  return NULL;			/* End of file. */
+}
+
+/* Rewind the shells file. */
+
+void
+setusershell ()
+{
+  default_index = 0;
+  if (shellstream == NULL)
+    shellstream = fopen (SHELLS_FILE, "r");
+  else
+    fseek (shellstream, 0L, 0);
+}
+
+/* Close the shells file. */
+
+void
+endusershell ()
+{
+  if (shellstream)
+    {
+      fclose (shellstream);
+      shellstream = NULL;
+    }
+}
+
+/* Allocate N bytes of memory dynamically, with error checking.  */
+
+static char *
+xmalloc (n)
+     unsigned n;
+{
+  char *p;
+
+  p = malloc (n);
+  if (p == 0)
+    {
+      fprintf (stderr, "virtual memory exhausted\n");
+      exit (1);
+    }
+  return p;
+}
+
+/* Reallocate space P to size N, with error checking.  */
+
+static char *
+xrealloc (p, n)
+     char *p;
+     unsigned n;
+{
+  p = realloc (p, n);
+  if (p == 0)
+    {
+      fprintf (stderr, "virtual memory exhausted\n");
+      exit (1);
+    }
+  return p;
+}
+
+/* Read a line from STREAM, removing any newline at the end.
+   Place the result in *NAME, which is malloc'd
+   and/or realloc'd as necessary and can start out NULL,
+   and whose size is passed and returned in *SIZE.
+
+   Return the number of characters placed in *NAME
+   if some nonempty sequence was found, otherwise 0.  */
+
+static int
+readname (name, size, stream)
+     char **name;
+     int *size;
+     FILE *stream;
+{
+  int c;
+  int name_index = 0;
+
+  if (*name == NULL)
+    {
+      *size = 10;
+      *name = (char *) xmalloc (*size);
+    }
+
+  /* Skip blank space.  */
+  while ((c = getc (stream)) != EOF && isspace (c))
+    /* Do nothing. */ ;
+  
+  while (c != EOF && !isspace (c))
+    {
+      (*name)[name_index++] = c;
+      while (name_index >= *size)
+	{
+	  *size *= 2;
+	  *name = (char *) xrealloc (*name, *size);
+	}
+      c = getc (stream);
+    }
+  (*name)[name_index] = '\0';
+  return name_index;
+}
+
+#ifdef TEST
+main ()
+{
+  char *s;
+
+  while (s = getusershell ())
+    puts (s);
+  exit (0);
+}
+#endif