realpath: Add realpath.py

Author: Expertcoderz

src/realpath.py

@@ -0,0 +1,132 @@
+#!/usr/bin/python3
+
+import os
+import sys
+from optparse import OptionParser
+
+# Note: os.path is used instead of pathlib because certain functionality such as
+# os.path.normpath() lack a pathlib equivalent.
+
+
+def realpath(opts, filenames: list[str]):
+    endchar = "\0" if opts.zero else "\n"
+
+    if opts.relative_to:
+        filenames = (os.path.join(opts.relative_to, name) for name in filenames)
+
+    failed = False
+
+    for name in filenames:
+        try:
+            if not opts.symlink_mode:
+                if opts.can_mode == "e":
+                    # raise an error if missing
+                    os.path.realpath(name, strict=True)
+
+                name = os.path.abspath(name)
+            else:
+                if opts.symlink_mode == "L":
+                    # resolve instances of ".." first
+                    name = os.path.normpath(name)
+
+                name = os.path.realpath(name, strict=opts.can_mode == "e")
+
+                if not opts.can_mode:
+                    # raise an error if directory missing
+                    os.path.realpath(os.path.dirname(name), strict=True)
+        except OSError as e:
+            failed = True
+
+            if not opts.quiet:
+                print(e, file=sys.stderr)
+        else:
+            if opts.relative_to and not opts.relative_base:
+                name = os.path.relpath(name, opts.relative_to)
+            elif opts.relative_base and not opts.relative_to:
+                name = os.path.relpath(name, opts.relative_base)
+
+            print(name, end=endchar)
+
+    if failed:
+        sys.exit(1)
+
+
+if __name__ == "__main__":
+    parser = OptionParser(
+        usage="Usage: %prog [OPTION]... FILE...",
+        description="Print the resolved path of each FILE.",
+        add_help_option=False,
+    )
+    parser.add_option("--help", action="help", help="show usage information and exit")
+
+    parser.add_option(
+        "-q", "--quiet", action="store_true", help="suppress error messages"
+    )
+
+    parser.add_option(
+        "-e",
+        "--canonicalize-existing",
+        dest="can_mode",
+        action="store_const",
+        const="e",
+        help="all path components must exist",
+    )
+    parser.add_option(
+        "-m",
+        "--canonicalize-missing",
+        dest="can_mode",
+        action="store_const",
+        const="m",
+        help="no path components need exist or be a directory",
+    )
+
+    parser.add_option(
+        "-L",
+        "--logical",
+        dest="symlink_mode",
+        action="store_const",
+        const="L",
+        help="resolve '..' components before symlinks",
+    )
+    parser.add_option(
+        "-P",
+        "--physical",
+        dest="symlink_mode",
+        action="store_const",
+        const="P",
+        default="P",
+        help="resolve symlinks as encountered (default)",
+    )
+    parser.add_option(
+        "-s",
+        "--strip",
+        "--no-symlinks",
+        dest="symlink_mode",
+        action="store_const",
+        const="",
+        help="do not resolve symlinks",
+    )
+
+    parser.add_option(
+        "--relative-to", metavar="DIR", help="resolve the path relative to DIR"
+    )
+    parser.add_option(
+        "--relative-base",
+        default="",
+        metavar="DIR",
+        help="print absolute paths except those below DIR",
+    )
+
+    parser.add_option(
+        "-z",
+        "--zero",
+        action="store_true",
+        help="terminate outputs with NUL instead of newline",
+    )
+
+    opts, args = parser.parse_args()
+
+    if not args:
+        parser.error("missing operand")
+
+    realpath(opts, args)