readlink: Add readlink.py

Author: Expertcoderz

src/readlink.py

@@ -0,0 +1,114 @@
+#!/usr/bin/python3
+
+import sys
+from optparse import OptionParser
+from pathlib import Path
+from typing import Callable
+
+
+def readlink_function(can_mode: str | None) -> Callable[[Path], str]:
+    match can_mode:
+        case None:
+            return lambda path: path.readlink()
+        case "f":
+            return (
+                lambda path: path.parent.resolve(strict=True)
+                .joinpath(path.name)
+                .resolve(strict=False)
+            )
+        case "e" | "m":
+            return lambda path: path.resolve(strict=can_mode == "e")
+
+
+def readlink(opts, paths: list[Path]):
+    # This is the precise behavior of GNU readlink regardless
+    # of in what order the -n and -z flags are specified.
+    endchar = "" if opts.no_newline else "\0" if opts.zero else "\n"
+
+    func = readlink_function(opts.can_mode)
+    failed = False
+
+    for path in paths:
+        try:
+            print(func(path), end=endchar)
+        except OSError as e:
+            failed = True
+
+            if opts.verbose:
+                print(e, file=sys.stderr)
+
+    if failed:
+        sys.exit(1)
+
+
+if __name__ == "__main__":
+    parser = OptionParser(
+        usage="Usage: %prog [OPTION]... FILE...",
+        description="Print the target of each symbolic link FILE.",
+        add_help_option=False,
+    )
+    parser.add_option("--help", action="help", help="show usage information and exit")
+
+    parser.add_option(
+        "-f",
+        "--canonicalize",
+        dest="can_mode",
+        action="store_const",
+        const="f",
+        help="all but the last path component must exist",
+    )
+    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(
+        "-n",
+        "--no-newline",
+        action="store_true",
+        help="do not delimit outputs (overrides -z)",
+    )
+    parser.add_option(
+        "-z",
+        "--zero",
+        action="store_true",
+        help="terminate outputs with NUL instead of newline",
+    )
+
+    parser.add_option(
+        "-q",
+        "--quiet",
+        "-s",
+        "--silent",
+        dest="verbose",
+        action="store_false",
+        default=False,
+        help="suppress error messages (default)",
+    )
+    parser.add_option(
+        "-v",
+        "--verbose",
+        dest="verbose",
+        action="store_true",
+        help="report errors",
+    )
+
+    opts, args = parser.parse_args()
+
+    if opts.no_newline and len(args) > 1:
+        print("ignoring --no-newline with multiple arguments", file=sys.stderr)
+        opts.no_newline = False
+
+    readlink(opts, map(Path, args))