London | SDC-Nov-25 | Pezhman Azizi | Sprint 4 | Implement shell Tools In Python

implement-shell-tools/cat/cat.py

@@ -0,0 +1,30 @@
+#!/usr/bin/env python3
+
+import sys
+import argparse
+
+# Create the argument parser – similar style to `count-containing-words`
+parser = argparse.ArgumentParser(
+    prog="cat",
+    description="Prints the contents of one or more files",
+)
+
+# positional argument: one or more paths
+parser.add_argument(
+    "paths",
+    nargs="+",
+    help="The file(s) to print",
+)
+
+args = parser.parse_args()
+
+# Loop over each path and print its content
+for path in args.paths:
+    try:
+        with open(path, "r", encoding="utf-8") as f:
+            for line in f:
+                # print line exactly as it appears in the file
+                sys.stdout.write(line)
+    except FileNotFoundError:
+        # match shell cat-style error message
+        sys.stderr.write(f"cat: {path}: No such file or directory\n")

implement-shell-tools/ls/ls.py

@@ -0,0 +1,56 @@
+#!/usr/bin/env python3
+
+import os
+import sys
+import argparse
+
+parser = argparse.ArgumentParser(
+    prog="ls",
+    description="Simple reimplementation of ls",
+)
+
+parser.add_argument(
+    "-1",
+    dest="one_per_line",
+    action="store_true",
+    help="List one entry per line",
+)
+
+parser.add_argument(
+    "-a",
+    dest="all_files",
+    action="store_true",
+    help="Do not ignore entries starting with .",
+)
+
+# Optional path (default = current directory)
+parser.add_argument(
+    "path",
+    nargs="?",
+    default=".",
+    help="Directory to list (default: current directory)",
+)
+
+args = parser.parse_args()
+
+# Get all items in the directory
+try:
+    entries = os.listdir(args.path)
+except FileNotFoundError:
+    sys.stderr.write(f"ls: cannot access '{args.path}': No such file or directory\n")
+    sys.exit(1)
+
+# Handle -a (hidden files)
+if not args.all_files:
+    entries = [e for e in entries if not e.startswith(".")]
+
+# Sort for stable behaviour
+entries.sort()
+
+# Output: -1 = one per line
+if args.one_per_line:
+    for entry in entries:
+        print(entry)
+else:
+    # default: space-separated
+    print(" ".join(entries))

implement-shell-tools/wc/wc.py

@@ -0,0 +1,106 @@
+#!/usr/bin/env python3
+
+import argparse
+import sys
+import os
+
+parser = argparse.ArgumentParser(
+    prog="wc",
+    description="Simple reimplementation of wc"
+)
+
+parser.add_argument(
+    "-l",
+    dest="count_lines",
+    action="store_true",
+    help="Print the line counts"
+)
+
+parser.add_argument(
+    "-w",
+    dest="count_words",
+    action="store_true",
+    help="Print the word counts"
+)
+
+parser.add_argument(
+    "-c",
+    dest="count_bytes",
+    action="store_true",
+    help="Print the byte counts"
+)
+
+parser.add_argument(
+    "paths",
+    nargs="+",
+    help="File(s) to process"
+)
+
+args = parser.parse_args()
+
+
+def wc_file(path):
+    """Return (lines, words, bytes) for a file."""
+    try:
+        with open(path, "r", encoding="utf-8") as f:
+            content = f.read()
+    except FileNotFoundError:
+        sys.stderr.write(f"wc: {path}: No such file or directory\n")
+        return None
+
+    lines = content.count("\n") + (1 if content and not content.endswith("\n") else 0)
+    words = len(content.split())
+    bytes_ = len(content.encode("utf-8"))
+
+    return lines, words, bytes_
+
+
+# If no flags are supplied, show all three
+show_all = not (args.count_lines or args.count_words or args.count_bytes)
+
+totals = [0, 0, 0]  # lines, words, bytes
+multiple_files = len(args.paths) > 1
+
+for path in args.paths:
+    result = wc_file(path)
+    if result is None:
+        continue
+
+    lines, words, bytes_ = result
+
+    totals[0] += lines
+    totals[1] += words
+    totals[2] += bytes_
+
+    output_parts = []
+
+    if show_all:
+        output_parts.extend([str(lines), str(words), str(bytes_)])
+    else:
+        if args.count_lines:
+            output_parts.append(str(lines))
+        if args.count_words:
+            output_parts.append(str(words))
+        if args.count_bytes:
+            output_parts.append(str(bytes_))
+
+    output_parts.append(path)
+    print(" ".join(output_parts))
+
+
+# If multiple files → print total line
+if multiple_files:
+    totals_output = []
+
+    if show_all:
+        totals_output.extend([str(totals[0]), str(totals[1]), str(totals[2])])
+    else:
+        if args.count_lines:
+            totals_output.append(str(totals[0]))
+        if args.count_words:
+            totals_output.append(str(totals[1]))
+        if args.count_bytes:
+            totals_output.append(str(totals[2]))
+
+    totals_output.append("total")
+    print(" ".join(totals_output))