cat: Add cat.py

Expertcoderz · Expertcoderz · commit 00526df8d513 · 2025-03-29T15:46:08.000Z
diff --git a/src/cat.py b/src/cat.py
@@ -0,0 +1,184 @@
+#!/usr/bin/python3
+
+import itertools
+import sys
+from io import BufferedReader
+from optparse import OptionParser
+from typing import BinaryIO, Generator
+
+
+def squeeze_blank_lines(io: BinaryIO) -> Generator[bytes]:
+    was_blank = False
+
+    for line in io:
+        is_blank = len(line) < 2
+
+        if was_blank and is_blank:
+            continue
+
+        yield line
+        was_blank = is_blank
+
+
+def number_lines(io: BinaryIO) -> Generator[bytes]:
+    for i, _ in enumerate(io):
+        yield f"{i + 1:>6}  ".encode()
+
+
+def number_nonblank_lines(io: BinaryIO) -> Generator[bytes]:
+    i = 1
+    for line in io:
+        if len(line) > 1:
+            yield f"{i:>6}  ".encode()
+            i += 1
+        else:
+            yield b""
+
+
+def format_chars(
+    data: bytes, show_ends: bool, show_tabs: bool, show_nonprinting: bool
+) -> Generator[bytes]:
+    for n in data:
+        if n == ord(b"\n"):
+            if show_ends:
+                yield b"$\n"
+                continue
+        elif n == ord(b"\t"):
+            if show_tabs:
+                yield b"^I"
+                continue
+        elif show_nonprinting and (n < 32 or n > 126):
+            if n < 32:
+                yield b"^" + (n + 64).to_bytes()
+            elif n == 127:
+                yield b"^?"
+            elif n < 128 + 32:
+                yield b"M-^" + (n - 128 + 64).to_bytes()
+            elif n < 128 + 127:
+                yield b"M-" + (n - 128).to_bytes()
+            else:
+                yield b"M-?"
+            continue
+
+        yield n.to_bytes()
+
+
+def format_lines(io: BinaryIO, *args) -> Generator[bytes]:
+    for line in io:
+        yield b"".join(format_chars(line, *args))
+
+
+def cat_io(opts, io: BinaryIO) -> None:
+    if opts.squeeze_blank:
+        io = squeeze_blank_lines(io)
+
+    io1, io2 = itertools.tee(io, 2)
+    gen1, gen2 = None, None
+
+    if opts.number_nonblank:
+        gen1 = number_nonblank_lines(io1)
+    elif opts.number:
+        gen1 = number_lines(io1)
+
+    if opts.show_ends or opts.show_tabs or opts.show_nonprinting:
+        gen2 = format_lines(io2, opts.show_ends, opts.show_tabs, opts.show_nonprinting)
+    else:
+        gen2 = io2
+
+    if gen1 and gen2:
+        for part1, part2 in zip(gen1, gen2, strict=True):
+            sys.stdout.buffer.write(part1 + part2)
+            sys.stdout.buffer.flush()
+    else:
+        for line in gen2:
+            sys.stdout.buffer.write(line)
+            sys.stdout.buffer.flush()
+
+
+def readlines_stdin() -> Generator[bytes]:
+    while True:
+        if line := sys.stdin.buffer.readline():
+            yield line
+        else:
+            # EOF (Ctrl-D)
+            break
+
+
+def cat(opts, filenames: list[str]):
+    generators = [
+        readlines_stdin() if name == "-" else open(name, "rb") for name in filenames
+    ]
+
+    try:
+        cat_io(opts, itertools.chain(*generators))
+    except KeyboardInterrupt:
+        print()
+        sys.exit(130)
+    finally:
+        for gen in generators:
+            # Close opened files other than stdin.
+            if isinstance(gen, BufferedReader):
+                gen.close()
+
+
+if __name__ == "__main__":
+    parser = OptionParser(
+        usage="Usage: %prog [OPTION]... [FILE]...",
+        description="Concatenate each FILE to standard output.",
+        add_help_option=False,
+    )
+    parser.add_option("--help", action="help", help="show usage information and exit")
+
+    parser.add_option(
+        "-E", "--show-ends", action="store_true", help="append '$' to each LF"
+    )
+    parser.add_option(
+        "-T", "--show-tabs", action="store_true", help="convert TABs to '^I'"
+    )
+    parser.add_option(
+        "-v",
+        "--show-nonprinting",
+        action="store_true",
+        help="show nonprinting characters except LF and TAB with ^ and M- notation",
+    )
+    parser.add_option(
+        "-A", "--show-all", action="store_true", help="equivalent to -vET"
+    )
+    parser.add_option("-e", action="store_true", help="equivalent to -vE")
+    parser.add_option("-t", action="store_true", help="equivalent to -vT")
+
+    parser.add_option(
+        "-n", "--number", action="store_true", help="number each output line"
+    )
+    parser.add_option(
+        "-b",
+        "--number-nonblank",
+        action="store_true",
+        help="number each nonempty output line (overrides -n)",
+    )
+
+    parser.add_option(
+        "-s",
+        "--squeeze-blank",
+        action="store_true",
+        help="collapse repeated empty output lines",
+    )
+
+    parser.add_option(
+        "-u", action="store_true", help="(ignored; present for POSIX compatibility)"
+    )
+
+    opts, args = parser.parse_args()
+
+    if opts.show_all:
+        opts.show_ends = True
+        opts.show_tabs = True
+        opts.show_nonprinting = True
+    elif opts.e:
+        opts.show_ends = True
+        opts.show_nonprinting = True
+    elif opts.t:
+        opts.show_tabs = True
+        opts.show_nonprinting = True
+
+    cat(opts, args or ["-"])
