LONDON | SDC-NOV-2025| JESUS DEL MORAL | Sprint 4 | Feature / Implement Shell Tools Python

implement-shell-tools/cat/script-02.py

@@ -0,0 +1,54 @@
+#!/usr/bin/env python3
+import sys
+import argparse
+
+def read_file(path, number_all, number_nonblank, line_counter):
+    """Reads a file and prints its contents with the requested numbering."""
+    try:
+        with open(path, "r") as f:
+            for line in f:
+                line_no_newline = line.rstrip("\n")
+
+                if number_all:
+                    print(f"{line_counter:6}\t{line_no_newline}")
+                    line_counter += 1
+
+                elif number_nonblank:
+                    if line_no_newline.strip():
+                        print(f"{line_counter:6}\t{line_no_newline}")
+                        line_counter += 1
+                    else:
+                        print("")  # blank line stays blank
+
+                else:
+                    print(line_no_newline)
+
+        return line_counter
+
+    except FileNotFoundError:
+        print(f"cat: {path}: No such file or directory", file=sys.stderr)
+        return line_counter
+
+
+def main():
+    parser = argparse.ArgumentParser(description="Simple cat implementation")
+    parser.add_argument("-n", action="store_true", help="number all lines")
+    parser.add_argument("-b", action="store_true", help="number non-blank lines")
+    parser.add_argument("files", nargs="+", help="files to read")
+
+    args = parser.parse_args()
+
+    # cat rule: if -b is used, ignore -n
+    number_all = args.n
+    number_nonblank = args.b
+    if number_nonblank:
+        number_all = False
+
+    line_counter = 1
+
+    for path in args.files:
+        line_counter = read_file(path, number_all, number_nonblank, line_counter)
+
+
+if __name__ == "__main__":
+    main()

implement-shell-tools/cat/script-cat.py

@@ -0,0 +1,54 @@
+#!/usr/bin/env python3
+import sys
+import argparse
+
+def read_file(path, number_all, number_nonblank, line_counter):
+    """Reads a file and prints its contents with the requested numbering."""
+    try:
+        with open(path, "r") as f:
+            for line in f:
+                line_no_newline = line.rstrip("\n")
+
+                if number_all:
+                    print(f"{line_counter:6}\t{line_no_newline}")
+                    line_counter += 1
+
+                elif number_nonblank:
+                    if line_no_newline.strip():
+                        print(f"{line_counter:6}\t{line_no_newline}")
+                        line_counter += 1
+                    else:
+                        print("")  # blank line stays blank
+
+                else:
+                    print(line_no_newline)
+
+        return line_counter
+
+    except FileNotFoundError:
+        print(f"cat: {path}: No such file or directory", file=sys.stderr)
+        return line_counter
+
+
+def main():
+    parser = argparse.ArgumentParser(description="Simple cat implementation")
+    parser.add_argument("-n", action="store_true", help="number all lines")
+    parser.add_argument("-b", action="store_true", help="number non-blank lines")
+    parser.add_argument("files", nargs="+", help="files to read")
+
+    args = parser.parse_args()
+
+    # cat rule: if -b is used, ignore -n
+    number_all = args.n
+    number_nonblank = args.b
+    if number_nonblank:
+        number_all = False
+
+    line_counter = 1
+
+    for path in args.files:
+        line_counter = read_file(path, number_all, number_nonblank, line_counter)
+
+
+if __name__ == "__main__":
+    main()

implement-shell-tools/ls/script-02.py

@@ -0,0 +1,55 @@
+#!/usr/bin/env python3
+
+import os
+import sys
+import argparse
+
+
+def list_directory(path, show_all):
+    """List contents of a directory, respecting the -a and -1 options."""
+
+    try:
+        entries = os.listdir(path)
+    except FileNotFoundError:
+        print(f"ls: cannot access '{path}': No such file or directory", file=sys.stderr)
+        return
+
+    # If -a is not provided, hide dotfiles
+    if not show_all:
+        entries = [e for e in entries if not e.startswith(".")]
+
+    # Sort alphabetically like ls normally does
+    entries.sort()
+
+    # Print one entry per line (-1 behaviour)
+    for entry in entries:
+        print(entry)
+
+
+def main():
+    parser = argparse.ArgumentParser(description="Simple ls implementation")
+    parser.add_argument(
+        "-a",
+        action="store_true",
+        help="include directory entries whose names begin with a dot",
+    )
+    parser.add_argument(
+        "-1",
+        dest="one_per_line",
+        action="store_true",
+        help="list one file per line",
+    )
+    parser.add_argument("path", nargs="?", default=".", help="directory to list")
+
+    args = parser.parse_args()
+
+    # Only -1 is supported, but it's always required in this assignment
+    if not args.one_per_line:
+        print("This program only supports the -1 option.", file=sys.stderr)
+        sys.exit(1)
+
+    list_directory(args.path, show_all=args.a)
+
+
+if __name__ == "__main__":
+    main()

implement-shell-tools/ls/script-ls.py

@@ -0,0 +1,79 @@
+#!/usr/bin/env python3
+
+import os
+import sys
+import argparse
+
+
+def list_directory(path, show_all, one_per_line):
+    try:
+        # If path is a file, just print it
+        if os.path.isfile(path):
+            print(path)
+            return
+
+        # If path is a directory, list its contents
+        if os.path.isdir(path):
+            entries = os.listdir(path)
+        else:
+            print(
+                f"ls: cannot access '{path}': No such file or directory",
+                file=sys.stderr,
+            )
+            return
+
+    except PermissionError:
+        print(
+            f"ls: cannot open directory '{path}': Permission denied",
+            file=sys.stderr,
+        )
+        return
+
+    # Hide dotfiles unless -a is used
+    if not show_all:
+        entries = [e for e in entries if not e.startswith(".")]
+
+    entries.sort()
+
+    # Output formatting
+    if one_per_line:
+        for entry in entries:
+            print(entry)
+    else:
+        print(" ".join(entries))
+
+
+def main():
+    parser = argparse.ArgumentParser(description="Simple ls implementation")
+
+    parser.add_argument(
+        "-a",
+        action="store_true",
+        help="include directory entries whose names begin with a dot",
+    )
+
+    parser.add_argument(
+        "-1",
+        dest="one_per_line",
+        action="store_true",
+        help="list one file per line",
+    )
+
+    parser.add_argument(
+        "path",
+        nargs="?",
+        default=".",
+        help="directory or file to list",
+    )
+
+    args = parser.parse_args()
+
+    list_directory(
+        args.path,
+        show_all=args.a,
+        one_per_line=args.one_per_line,
+    )
+
+
+if __name__ == "__main__":
+    main()

implement-shell-tools/wc/script-02.py

@@ -0,0 +1,83 @@
+#!/usr/bin/env python3
+import argparse
+import sys
+
+
+def count_file(path):
+    """Return (lines, words, bytes) for the given file."""
+    try:
+        with open(path, "rb") as f:
+            content = f.read()
+    except FileNotFoundError:
+        print(f"wc: {path}: No such file or directory", file=sys.stderr)
+        return None
+
+    text = content.decode("utf-8", errors="replace")
+    lines = text.count("\n")
+    words = len(text.split())
+    bytes_ = len(content)
+
+    return lines, words, bytes_
+
+
+def print_result(counts, path, show_l, show_w, show_c):
+    """Format and print output for a file."""
+    lines, words, bytes_ = counts
+
+    # If no specific flag is given → print all three (like wc)
+    if not (show_l or show_w or show_c):
+        print(f"{lines:>7} {words:>7} {bytes_:>7} {path}")
+        return
+
+    out = []
+    if show_l:
+        out.append(f"{lines:>7}")
+    if show_w:
+        out.append(f"{words:>7}")
+    if show_c:
+        out.append(f"{bytes_:>7}")
+
+    print(" ".join(out), path)
+
+
+def main():
+    parser = argparse.ArgumentParser(description="Simple wc implementation")
+    parser.add_argument("-l", action="store_true", help="count lines")
+    parser.add_argument("-w", action="store_true", help="count words")
+    parser.add_argument("-c", action="store_true", help="count bytes")
+    parser.add_argument("paths", nargs="+", help="file(s) to process")
+
+    args = parser.parse_args()
+
+    total_lines = total_words = total_bytes = 0
+    multiple_files = len(args.paths) > 1
+
+    for path in args.paths:
+        result = count_file(path)
+        if result is None:
+            continue
+
+        lines, words, bytes_ = result
+        print_result(result, path, args.l, args.w, args.c)
+
+        total_lines += lines
+        total_words += words
+        total_bytes += bytes_
+
+    # Print totals if more than one file
+    if multiple_files:
+        if not (args.l or args.w or args.c):
+            print(f"{total_lines:>7} {total_words:>7} {total_bytes:>7} total")
+        else:
+            out = []
+            if args.l:
+                out.append(f"{total_lines:>7}")
+            if args.w:
+                out.append(f"{total_words:>7}")
+            if args.c:
+                out.append(f"{total_bytes:>7}")
+            print(" ".join(out), "total")
+
+
+if __name__ == "__main__":
+    main()