Birmingham | 2026-MAR-SDC | Joy Opachavalit | Sprint 4 | Implement shell tools in python

.gitignore

@@ -1 +1,4 @@
 node_modules
+
+# Ignore Python virtual environments
+implement-cowsay/.venv/

implement-shell-tools/cat/cat.py

@@ -0,0 +1,51 @@
+#!/usr/bin/env python3
+
+import sys
+
+def cat_file(file, options, line_number):
+    try:
+        with open(file, 'r', encoding='utf-8') as f:
+            lines = f.readlines()
+
+        for line in lines:
+            if options['number_non_blank'] and line.strip():
+                print(f"{line_number:6}\t{line}", end='')
+                line_number += 1
+            elif options['number_all']:
+                print(f"{line_number:6}\t{line}", end='')
+                line_number += 1
+            else:
+                print(line, end='')
+
+        return line_number
+    except FileNotFoundError:
+        print(f"cat: {file}: No such file or directory", file=sys.stderr)
+        sys.exit(1)
+
+def main():
+    args = sys.argv[1:]
+    options = {
+        'number_all': False,
+        'number_non_blank': False,
+    }
+
+    files = []
+
+    for arg in args:
+        if arg == '-n':
+            options['number_all'] = True
+        elif arg == '-b':
+            options['number_non_blank'] = True
+        else:
+            files.append(arg)
+
+    if not files:
+        print("Usage: cat [-n | -b] <file>...", file=sys.stderr)
+        sys.exit(1)
+
+    line_number = 1
+    for file in files:
+        line_number = cat_file(file, options, line_number)
+
+if __name__ == "__main__":
+    main()

implement-shell-tools/ls/ls.py

@@ -0,0 +1,65 @@
+#!/usr/bin/env python3
+
+import locale
+import os
+import sys
+
+
+def parse_args(args):
+    one_per_line = False
+    show_all = False
+    paths = []
+
+    for arg in args:
+        if arg.startswith("-") and arg != "-":
+            for flag in arg[1:]:
+                if flag == "1":
+                    one_per_line = True
+                elif flag == "a":
+                    show_all = True
+                else:
+                    print(f"ls: invalid option -- '{flag}'", file=sys.stderr)
+                    sys.exit(1)
+        else:
+            paths.append(arg)
+
+    if not one_per_line:
+        print("Usage: ls.py -1 [-a] [path]", file=sys.stderr)
+        sys.exit(1)
+
+    if len(paths) > 1:
+        print("Usage: ls.py -1 [-a] [path]", file=sys.stderr)
+        sys.exit(1)
+
+    return show_all, (paths[0] if paths else ".")
+
+
+def list_entries(path, show_all):
+    try:
+        entries = os.listdir(path)
+    except FileNotFoundError:
+        print(f"ls: cannot access '{path}': No such file or directory", file=sys.stderr)
+        sys.exit(1)
+    except NotADirectoryError:
+        print(os.path.basename(path))
+        return
+
+    if show_all:
+        entries = [".", ".."] + entries
+    else:
+        entries = [name for name in entries if not name.startswith(".")]
+
+    locale.setlocale(locale.LC_COLLATE, "")
+    entries = sorted(entries, key=locale.strxfrm)
+
+    for entry in entries:
+        print(entry)
+
+
+def main():
+    show_all, path = parse_args(sys.argv[1:])
+    list_entries(path, show_all)
+
+
+if __name__ == "__main__":
+    main()

implement-shell-tools/wc/wc.py

@@ -0,0 +1,107 @@
+#!/usr/bin/env python3
+
+import sys
+
+
+def count_file(file):
+    try:
+        with open(file, 'r', encoding='utf-8') as f:
+            data = f.read()
+
+        lines = data.count('\n')
+        words = len(data.split())
+        bytes_count = len(data.encode('utf-8'))
+
+        return lines, words, bytes_count
+    except FileNotFoundError:
+        print(f"wc: {file}: No such file or directory", file=sys.stderr)
+        sys.exit(1)
+
+
+def selected_keys(options):
+    if not any(options.values()):
+        return ['lines', 'words', 'bytes']
+
+    keys = []
+    if options['lines']:
+        keys.append('lines')
+    if options['words']:
+        keys.append('words')
+    if options['bytes']:
+        keys.append('bytes')
+    return keys
+
+
+def values_for_keys(counts, keys):
+    lines, words, bytes_count = counts
+    mapping = {
+        'lines': lines,
+        'words': words,
+        'bytes': bytes_count,
+    }
+    return [mapping[key] for key in keys]
+
+
+def print_rows(rows, keys):
+    align_columns = len(keys) > 1 or len(rows) > 1
+
+    if not align_columns:
+        values, name = rows[0]
+        print(f"{values[0]} {name}")
+        return
+
+    widths = []
+    for index in range(len(keys)):
+        max_len = max(len(str(values[index])) for values, _ in rows)
+        widths.append(max(3, max_len))
+
+    for values, name in rows:
+        formatted_values = " ".join(
+            f"{value:>{width}}" for value, width in zip(values, widths)
+        )
+        print(f"{formatted_values} {name}")
+
+def main():
+    args = sys.argv[1:]
+    options = {
+        'lines': False,
+        'words': False,
+        'bytes': False,
+    }
+
+    files = []
+
+    for arg in args:
+        if arg == '-l':
+            options['lines'] = True
+        elif arg == '-w':
+            options['words'] = True
+        elif arg == '-c':
+            options['bytes'] = True
+        else:
+            files.append(arg)
+
+    if not files:
+        print("Usage: wc [-l | -w | -c] <file>...", file=sys.stderr)
+        sys.exit(1)
+
+    total_lines = 0
+    total_words = 0
+    total_bytes = 0
+    keys = selected_keys(options)
+    rows = []
+
+    for file in files:
+        lines, words, bytes_count = count_file(file)
+        total_lines += lines
+        total_words += words
+        total_bytes += bytes_count
+        rows.append((values_for_keys((lines, words, bytes_count), keys), file))
+
+    if len(files) > 1:
+        rows.append((values_for_keys((total_lines, total_words, total_bytes), keys), 'total'))
+
+    print_rows(rows, keys)
+
+if __name__ == "__main__":
+    main()