implemented shell tools (cat, ls, wc) in python

Author: Fradoka

.vscode/settings.json

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+{
+    "githubPullRequests.ignoredPullRequestBranches": [
+        "main"
+    ]
+}

implement-shell-tools/cat/cat.py

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+#!/usr/bin/env python3
+import argparse
+
+# implement-shell-tools/cat/cat.py
+def main():
+    parser = argparse.ArgumentParser(
+    prog="cat",
+    description="Implements a simple version of the 'cat' command to read and display file contents."
+    )
+
+    parser.add_argument("-n", help="Number lines", action="store_true")
+    parser.add_argument("-b", help="Number non-blank lines", action="store_true")
+    parser.add_argument("path", nargs="+", help="The file to search")
+
+    args = parser.parse_args()
+
+    for file_path in args.path:
+        try:
+            with open(file_path, 'r') as file:
+                content = file.read()
+                lines = content.split("\n")
+                line_number = 1
+                non_blank_line_number = 1
+
+                for i, line in enumerate(lines):
+                    if i == len(lines) - 1 and line == "":  # Skip the last empty line if it exists
+                        break
+                    prefix = ""
+                    if args.n:
+                        prefix = str(line_number).rjust(6) + " "
+                    elif args.b and line != "":
+                        prefix = str(non_blank_line_number).rjust(6) + " "
+                    print(prefix + line)
+                    line_number += 1
+                    if line != "":
+                        non_blank_line_number += 1
+
+        except FileNotFoundError:
+            print(f"cat: {file_path}: No such file or directory")
+        except Exception as e:
+            print(f"cat: {file_path}: {e}")
+
+if __name__ == "__main__":
+    main()

implement-shell-tools/ls/ls.py

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+import argparse
+import os
+
+# implement-shell-tools/ls/ls.py
+def main():
+    parser = argparse.ArgumentParser(
+    prog="ls",
+    description="Implements a simple version of the 'ls' command to list files in a directory."
+    )
+
+    parser.add_argument("-1", help="", action="store_true")
+    parser.add_argument("-a", help="", action="store_true")
+    parser.add_argument("directory", nargs="?", default=".", help="The directory to search")
+
+    args = parser.parse_args()
+
+    try:
+        files = os.listdir(args.directory)
+
+        if not args.a:
+            files = [f for f in files if not f.startswith(".")]
+        
+        files = sorted(files)
+
+        for f in files:
+            print(f)
+
+    except FileNotFoundError:
+        print(f"ls: {args.directory}: No such file or directory")
+    except NotADirectoryError:
+        print(args.directory)
+    except Exception as e:
+        print(f"ls: {args.directory}: {e}")
+
+if __name__ == "__main__":
+    main()

implement-shell-tools/wc/wc.py

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+import argparse
+import sys
+
+# implement-shell-tools/wc/wc.py
+def wc_file(path):
+    """Return (lines, words, bytes) for a given file."""
+    with open(path, "r", encoding="utf-8") as f:
+        text = f.read()
+    lines = text.count("\n")
+    words = len(text.split())
+    chars = len(text.encode("utf-8"))  # byte count
+    return lines, words, chars
+
+
+def main():
+    parser = argparse.ArgumentParser(
+    prog="wc",
+    description="Implements a simple version of the 'wc' command to count lines, words, and characters in text files."
+    )
+
+    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 characters")
+    parser.add_argument("path", nargs="+", help="The files to read")
+
+    args = parser.parse_args()
+
+    if not (args.l or args.w or args.c):
+        args.l = args.w = args.c = True  # Default to all counts if none specified
+
+    total_lines = total_words = total_chars = 0
+
+    for file_path in args.path:
+        try:
+            lines, words, chars = wc_file(file_path)
+            total_lines += lines
+            total_words += words
+            total_chars += chars
+
+            counts = []
+            if args.l:
+                counts.append(str(lines))
+            if args.w:
+                counts.append(str(words))
+            if args.c:
+                counts.append(str(chars))
+            counts.append(file_path)
+            print(" ".join(counts))
+
+        except FileNotFoundError:
+            print(f"wc: {file_path}: No such file or directory", file=sys.stderr)
+        except Exception as e:
+            print(f"wc: {file_path}: {e}", file=sys.stderr)
+
+    if len(args.path) > 1:
+        counts = []
+        if args.l:
+            counts.append(str(total_lines))
+        if args.w:
+            counts.append(str(total_words))
+        if args.c:
+            counts.append(str(total_chars))
+        counts.append("total")
+        print(" ".join(counts))
+
+if __name__ == "__main__":
+    main()