Added new file realpath.

1 files changed, 278 insertions, 0 deletions

diff --git a/realpath.c b/realpath.c
new file mode 100644
index 0000000..6ed5f05
--- /dev/null
+++ b/realpath.c
@@ -0,0 +1,278 @@
+/* realpath - print the resolved path
+   Copyright (C) 2011-2020 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 3 of the License, 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, see <https://www.gnu.org/licenses/>.  */
+
+/* Written by Pádraig Brady.  */
+
+#include <config.h>
+#include <getopt.h>
+#include <stdio.h>
+#include <sys/types.h>
+
+#include "system.h"
+#include "canonicalize.h"
+#include "die.h"
+#include "error.h"
+#include "relpath.h"
+
+/* The official name of this program (e.g., no 'g' prefix).  */
+#define PROGRAM_NAME "realpath"
+
+#define AUTHORS proper_name ("Padraig Brady")
+
+enum
+{
+  RELATIVE_TO_OPTION = CHAR_MAX + 1,
+  RELATIVE_BASE_OPTION
+};
+
+static bool verbose = true;
+static bool logical;
+static bool use_nuls;
+static const char *can_relative_to;
+static const char *can_relative_base;
+
+static struct option const longopts[] =
+{
+  {"canonicalize-existing", no_argument, NULL, 'e'},
+  {"canonicalize-missing", no_argument, NULL, 'm'},
+  {"relative-to", required_argument, NULL, RELATIVE_TO_OPTION},
+  {"relative-base", required_argument, NULL, RELATIVE_BASE_OPTION},
+  {"quiet", no_argument, NULL, 'q'},
+  {"strip", no_argument, NULL, 's'},
+  {"no-symlinks", no_argument, NULL, 's'},
+  {"zero", no_argument, NULL, 'z'},
+  {"logical", no_argument, NULL, 'L'},
+  {"physical", no_argument, NULL, 'P'},
+  {GETOPT_HELP_OPTION_DECL},
+  {GETOPT_VERSION_OPTION_DECL},
+  {NULL, 0, NULL, 0}
+};
+
+void
+usage (int status)
+{
+  if (status != EXIT_SUCCESS)
+    emit_try_help ();
+  else
+    {
+      printf (_("Usage: %s [OPTION]... FILE...\n"), program_name);
+      fputs (_("\
+Print the resolved absolute file name;\n\
+all but the last component must exist\n\
+\n\
+"), stdout);
+      fputs (_("\
+  -e, --canonicalize-existing  all components of the path must exist\n\
+  -m, --canonicalize-missing   no path components need exist or be a directory\
+\n\
+  -L, --logical                resolve '..' components before symlinks\n\
+  -P, --physical               resolve symlinks as encountered (default)\n\
+  -q, --quiet                  suppress most error messages\n\
+      --relative-to=DIR        print the resolved path relative to DIR\n\
+      --relative-base=DIR      print absolute paths unless paths below DIR\n\
+  -s, --strip, --no-symlinks   don't expand symlinks\n\
+  -z, --zero                   end each output line with NUL, not newline\n\
+\n\
+"), stdout);
+      fputs (HELP_OPTION_DESCRIPTION, stdout);
+      fputs (VERSION_OPTION_DESCRIPTION, stdout);
+      emit_ancillary_info (PROGRAM_NAME);
+    }
+  exit (status);
+}
+
+/* A wrapper around canonicalize_filename_mode(),
+   to call it twice when in LOGICAL mode.  */
+static char *
+realpath_canon (const char *fname, int can_mode)
+{
+  char *can_fname = canonicalize_filename_mode (fname, can_mode);
+  if (logical && can_fname)  /* canonicalize again to resolve symlinks.  */
+    {
+      can_mode &= ~CAN_NOLINKS;
+      char *can_fname2 = canonicalize_filename_mode (can_fname, can_mode);
+      free (can_fname);
+      return can_fname2;
+    }
+  return can_fname;
+}
+
+/* Test whether canonical prefix is parent or match of path.  */
+static bool _GL_ATTRIBUTE_PURE
+path_prefix (const char *prefix, const char *path)
+{
+  /* We already know prefix[0] and path[0] are '/'.  */
+  prefix++;
+  path++;
+
+  /* '/' is the prefix of everything except '//' (since we know '//'
+     is only present after canonicalization if it is distinct).  */
+  if (!*prefix)
+    return *path != '/';
+
+  /* Likewise, '//' is a prefix of any double-slash path.  */
+  if (*prefix == '/' && !prefix[1])
+    return *path == '/';
+
+  /* Any other prefix has a non-slash portion.  */
+  while (*prefix && *path)
+    {
+      if (*prefix != *path)
+        break;
+      prefix++;
+      path++;
+    }
+  return (!*prefix && (*path == '/' || !*path));
+}
+
+static bool
+isdir (const char *path)
+{
+  struct stat sb;
+  if (stat (path, &sb) != 0)
+    die (EXIT_FAILURE, errno, _("cannot stat %s"), quoteaf (path));
+  return S_ISDIR (sb.st_mode);
+}
+
+static bool
+process_path (const char *fname, int can_mode)
+{
+  char *can_fname = realpath_canon (fname, can_mode);
+  if (!can_fname)
+    {
+      if (verbose)
+        error (0, errno, "%s", quotef (fname));
+      return false;
+    }
+
+  if (!can_relative_to
+      || (can_relative_base && !path_prefix (can_relative_base, can_fname))
+      || (can_relative_to && !relpath (can_fname, can_relative_to, NULL, 0)))
+    fputs (can_fname, stdout);
+
+  putchar (use_nuls ? '\0' : '\n');
+
+  free (can_fname);
+
+  return true;
+}
+
+int
+main (int argc, char **argv)
+{
+  bool ok = true;
+  int can_mode = CAN_ALL_BUT_LAST;
+  const char *relative_to = NULL;
+  const char *relative_base = NULL;
+
+  initialize_main (&argc, &argv);
+  set_program_name (argv[0]);
+  setlocale (LC_ALL, "");
+  bindtextdomain (PACKAGE, LOCALEDIR);
+  textdomain (PACKAGE);
+
+  atexit (close_stdout);
+
+  while (1)
+    {
+      int c = getopt_long (argc, argv, "eLmPqsz", longopts, NULL);
+      if (c == -1)
+        break;
+      switch (c)
+        {
+        case 'e':
+          can_mode &= ~CAN_MODE_MASK;
+          can_mode |= CAN_EXISTING;
+          break;
+        case 'm':
+          can_mode &= ~CAN_MODE_MASK;
+          can_mode |= CAN_MISSING;
+          break;
+        case 'L':
+          can_mode |= CAN_NOLINKS;
+          logical = true;
+          break;
+        case 's':
+          can_mode |= CAN_NOLINKS;
+          logical = false;
+          break;
+        case 'P':
+          can_mode &= ~CAN_NOLINKS;
+          logical = false;
+          break;
+        case 'q':
+          verbose = false;
+          break;
+        case 'z':
+          use_nuls = true;
+          break;
+        case RELATIVE_TO_OPTION:
+          relative_to = optarg;
+          break;
+        case RELATIVE_BASE_OPTION:
+          relative_base = optarg;
+          break;
+        case_GETOPT_HELP_CHAR;
+        case_GETOPT_VERSION_CHAR (PROGRAM_NAME, AUTHORS);
+        default:
+          usage (EXIT_FAILURE);
+        }
+    }
+
+  if (optind >= argc)
+    {
+      error (0, 0, _("missing operand"));
+      usage (EXIT_FAILURE);
+    }
+
+  if (relative_base && !relative_to)
+    relative_to = relative_base;
+
+  bool need_dir = (can_mode & CAN_MODE_MASK) == CAN_EXISTING;
+  if (relative_to)
+    {
+      can_relative_to = realpath_canon (relative_to, can_mode);
+      if (!can_relative_to)
+        die (EXIT_FAILURE, errno, "%s", quotef (relative_to));
+      if (need_dir && !isdir (can_relative_to))
+        die (EXIT_FAILURE, ENOTDIR, "%s", quotef (relative_to));
+    }
+  if (relative_base == relative_to)
+    can_relative_base = can_relative_to;
+  else if (relative_base)
+    {
+      char *base = realpath_canon (relative_base, can_mode);
+      if (!base)
+        die (EXIT_FAILURE, errno, "%s", quotef (relative_base));
+      if (need_dir && !isdir (base))
+        die (EXIT_FAILURE, ENOTDIR, "%s", quotef (relative_base));
+      /* --relative-to is a no-op if it does not have --relative-base
+           as a prefix */
+      if (path_prefix (base, can_relative_to))
+        can_relative_base = base;
+      else
+        {
+          free (base);
+          can_relative_base = can_relative_to;
+          can_relative_to = NULL;
+        }
+    }
+
+  for (; optind < argc; ++optind)
+    ok &= process_path (argv[optind], can_mode);
+
+  return ok ? EXIT_SUCCESS : EXIT_FAILURE;
+}