implement-shell-tools-in-python

Author: shaghayeghfar

implement-shell-tools/cat/cat.py

@@ -0,0 +1,66 @@
+import argparse
+import glob
+
+# create argument parser
+parser = argparse.ArgumentParser(description="Simple cat tool")
+
+parser.add_argument("files", nargs="+", help="files to read")
+parser.add_argument("-n", action="store_true", help="number all lines")
+parser.add_argument("-b", action="store_true", help="number non-empty lines")
+
+args = parser.parse_args()
+
+# if -b is used, ignore -n
+if args.b:
+    args.n = False
+
+line_number = 1
+
+
+# expand *.txt into real file names
+def get_files(file_patterns):
+    files = []
+    for pattern in file_patterns:
+        matched = glob.glob(pattern)
+
+        if matched:
+            files.extend(matched)
+        else:
+            files.append(pattern)
+
+    return files
+
+
+def print_file(file_name):
+    global line_number
+
+    try:
+        with open(file_name, "r") as f:
+            for line in f:
+
+                # -b → number only non-empty lines
+                if args.b:
+                    if line.strip():   # not empty
+                        print(f"{line_number}\t{line}", end="")
+                        line_number += 1
+                    else:
+                        print(line, end="")
+
+                # -n → number all lines
+                elif args.n:
+                    print(f"{line_number}\t{line}", end="")
+                    line_number += 1
+
+                # no flags
+                else:
+                    print(line, end="")
+
+    except FileNotFoundError:
+        print(f"Error: {file_name} not found")
+
+
+# main program
+files = get_files(args.files)
+
+for file in files:
+    print_file(file)

implement-shell-tools/ls/ls.py

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+import argparse
+import os
+
+# create parser
+parser = argparse.ArgumentParser(description="Simple ls tool")
+
+parser.add_argument("-1", dest="one", action="store_true", help="one item per line")
+parser.add_argument("-a", action="store_true", help="show hidden files")
+parser.add_argument("path", nargs="?", default=".", help="directory path")
+
+args = parser.parse_args()
+
+
+def list_files(path):
+    try:
+        files = os.listdir(path)
+
+        # if -a is NOT used, hide files starting with "."
+        if not args.a:
+            files = [f for f in files if not f.startswith(".")]
+
+        # sort like real ls
+        files.sort()
+
+        # print results
+        if args.one:
+            for f in files:
+                print(f)
+        else:
+            print("  ".join(files))
+
+    except FileNotFoundError:
+        print(f"Error: {path} not found")
+
+
+# run
+list_files(args.path)

implement-shell-tools/wc/wc.py

@@ -0,0 +1,78 @@
+import argparse
+import glob
+
+# create parser
+parser = argparse.ArgumentParser(description="Simple wc tool")
+
+parser.add_argument("files", nargs="+", help="files to read")
+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")
+
+args = parser.parse_args()
+
+
+# expand *.txt
+def get_files(file_patterns):
+    files = []
+    for pattern in file_patterns:
+        matched = glob.glob(pattern)
+        if matched:
+            files.extend(matched)
+        else:
+            files.append(pattern)
+    return files
+
+
+def count_file(file_name):
+    try:
+        with open(file_name, "r") as f:
+            text = f.read()
+
+            lines = text.count("\n")
+            words = len(text.split())
+            chars = len(text)
+
+            return lines, words, chars
+
+    except FileNotFoundError:
+        print(f"Error: {file_name} not found")
+        return 0, 0, 0
+
+
+def print_result(lines, words, chars, file_name):
+    # if no flags → show all
+    if not args.l and not args.w and not args.c:
+        print(lines, words, chars, file_name)
+
+    else:
+        output = []
+
+        if args.l:
+            output.append(str(lines))
+        if args.w:
+            output.append(str(words))
+        if args.c:
+            output.append(str(chars))
+
+        output.append(file_name)
+        print(" ".join(output))
+
+
+# main
+files = get_files(args.files)
+
+total_lines = total_words = total_chars = 0
+
+for file in files:
+    lines, words, chars = count_file(file)
+
+    total_lines += lines
+    total_words += words
+    total_chars += chars
+
+    print_result(lines, words, chars, file)
+
+# if multiple files → show total
+if len(files) > 1:
+    print_result(total_lines, total_words, total_chars, "total")