Manchester | 25-SDC-Nov | Rahwa Haile | Sprint 4 | Implement shell tools (cat, ls, wc) in Python

implement-shell-tools/.gitignore

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+.venv/
+__pycache__/
+*.pyc

implement-shell-tools/cat/sample-files/mycat.py

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+#!/usr/bin/env python3
+import sys
+import os
+
+def print_file(filename, number_all=False, number_nonempty=False):
+    try:
+        with open(filename, 'r') as f:
+            lines = f.readlines()
+    except FileNotFoundError:
+        print(f"cat: {filename}: No such file")
+        return
+
+    counter = 1
+    for line in lines:
+        line = line.rstrip('\n')
+        if number_all:
+            print(f"{counter:6}  {line}")
+            counter += 1
+        elif number_nonempty:
+            if line.strip():
+                print(f"{counter:6}  {line}")
+                counter += 1
+            else:
+                print(line)
+        else:
+            print(line)
+
+def main():
+    import argparse
+
+    parser = argparse.ArgumentParser(description="A Python implementation of cat")
+    parser.add_argument('files', nargs='+', help="Files to print")
+    parser.add_argument('-n', '--number-all', action='store_true', help="Number all lines")
+    parser.add_argument('-b', '--number-nonempty', action='store_true', help="Number non-empty lines")
+    args = parser.parse_args()
+
+    for file in args.files:
+        print_file(file, number_all=args.number_all, number_nonempty=args.number_nonempty)
+
+if __name__ == "__main__":
+    main()

implement-shell-tools/ls/sample-files/myls.py

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+#!/usr/bin/env python3
+import argparse
+import os
+
+def list_directory(dir_path, show_all):
+    if not os.path.exists(dir_path):
+        print(f"ls: cannot access '{dir_path}': No such file or directory")
+        return
+
+    if os.path.isfile(dir_path):
+        print(dir_path)
+        return
+
+    try:
+        entries = os.listdir(dir_path)
+    except PermissionError:
+        print(f"ls: cannot access '{dir_path}': Permission denied")
+        return
+
+    if not show_all:
+        entries = [e for e in entries if not e.startswith(".")]
+    else:
+        entries = [".", ".."] + entries
+
+    entries.sort()
+    for e in entries:
+        print(e)
+
+def main():
+    parser = argparse.ArgumentParser(description="Custom implementation of ls")
+    parser.add_argument("-1", action="store_true", help="list one file per line (default)")
+    parser.add_argument("-a", "--all", action="store_true", help="include hidden files")
+    parser.add_argument("dir", nargs="?", default=".", help="directory to list")
+
+    args = parser.parse_args()
+
+    list_directory(args.dir, args.all)
+
+if __name__ == "__main__":
+    main()

implement-shell-tools/wc/sample-files/mywc.py

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+#!/usr/bin/env python3
+import argparse
+import glob
+import os
+
+def count_lines(text):
+    if not text:
+        return 0
+    lines = text.splitlines()
+    return len(lines)
+
+def count_words(text):
+    return len([w for w in text.split() if w])
+
+def count_chars(text):
+    return len(text.encode('utf-8'))
+
+def wc_file(filename, options):
+    try:
+        with open(filename, "r", encoding="utf-8") as f:
+            text = f.read()
+    except FileNotFoundError:
+        print(f"wc: {filename}: No such file")
+        return None
+
+    lines = count_lines(text)
+    words = count_words(text)
+    chars = count_chars(text)
+
+    padding = 7
+    if options.lines and not options.words and not options.chars:
+        output = f"{lines} {filename}"
+    elif options.words and not options.lines and not options.chars:
+        output = f"{words} {filename}"
+    elif options.chars and not options.lines and not options.words:
+        output = f"{chars} {filename}"
+    else:
+        output = f"{str(lines).rjust(padding)} {str(words).rjust(padding)} {str(chars).rjust(padding)} {filename}"
+
+    print(output)
+    return {"lines": lines, "words": words, "chars": chars}
+
+def main():
+    parser = argparse.ArgumentParser(description="Custom implementation of wc")
+    parser.add_argument("-l", "--lines", action="store_true", help="count lines")
+    parser.add_argument("-w", "--words", action="store_true", help="count words")
+    parser.add_argument("-c", "--chars", action="store_true", help="count characters")
+    parser.add_argument("files", nargs="+", help="files or wildcard patterns")
+    args = parser.parse_args()
+
+    all_files = []
+    for pattern in args.files:
+        expanded = glob.glob(pattern)
+        if not expanded:
+            print(f"wc: {pattern}: No such file or directory")
+        all_files.extend(expanded)
+
+    total_lines = total_words = total_chars = 0
+
+    for file in all_files:
+        result = wc_file(file, args)
+        if result:
+            total_lines += result["lines"]
+            total_words += result["words"]
+            total_chars += result["chars"]
+
+    padding = 7
+    if len(all_files) > 1:
+        if args.lines and not args.words and not args.chars:
+            print(f"{total_lines} total")
+        elif args.words and not args.lines and not args.chars:
+            print(f"{total_words} total")
+        elif args.chars and not args.lines and not args.words:
+            print(f"{total_chars} total")
+        else:
+            print(f"{str(total_lines).rjust(padding)} {str(total_words).rjust(padding)} {str(total_chars).rjust(padding)} total")
+
+if __name__ == "__main__":
+    main()