WestMidlands| SDC-NOV-2025| SARA TAHIR | Sprint 4| Feature/Implement Shell Tools Python

implement-shell-tools/cat/cat.py

@@ -0,0 +1,62 @@
+import argparse
+import sys
+import glob # to find file paths and match patterns
+
+
+
+def parse_args():
+    parser = argparse.ArgumentParser(
+        prog = "cat",
+        description= "copying cat commands behavior with -n and -b flags"
+    )
+    parser.add_argument("-n", "--number", action="store_true", help="Number all output lines")  #with store true argument behaves like a boolean, flag present returns true, not present = false.
+    parser.add_argument("-b", "--number-nonblank", action="store_true", help="Number non-empty output lines")
+    parser.add_argument("files", nargs="+", help="Files to read (supports shell globs)") # accepts one or more files names or glob patterns.
+    return parser.parse_args()
+
+#Uses glob to expand patterns like *.txt.
+def expand_files(patterns):
+    expanded = []
+    for p in patterns:
+        matches = glob.glob(p)
+        if matches:
+            expanded.extend(sorted(matches))  # predictable order
+        else:
+            print(f"cat: {p}: No such file", file=sys.stderr) #Prints an error if a pattern matches nothing.
+    return expanded
+
+def cat_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
+#Applies numbering rules depending on flags.
+    line_num = 1
+    for line in lines:
+        line = line.rstrip('\n')
+        if number_all:
+            print(f"{line_num:6}  {line}")
+            line_num += 1
+        elif number_nonempty:
+            if line.strip():
+                print(f"{line_num:6}  {line}")
+                line_num+= 1
+            else:
+                print(line)
+        else:
+            print(line)
+
+def main():
+    args = parse_args() #return an args obj
+    files = expand_files(args.files) #list of filenames or patterns user typed passed to expand_files helper that uses glob module to expand patterns to actual file paths
+    if not files:
+        sys.exit(1)  #programs exits with status code 1- signals and error if no files were found
+
+#looping through each file path on expanded list
+    for file in files: 
+        cat_file(file, number_all=args.number, number_nonempty=args.number_nonblank)
+
+if __name__ == "__main__":
+    main()

implement-shell-tools/ls/ls.py

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+import argparse
+import os    #interacting with the filesystem (paths, directories)
+import sys   #access to system streams (stdout, stderr) and arguments
+
+def parseargs():
+    parser = argparse.ArgumentParser(
+        prog = "ls",
+        description = "ls clone to -1 and -a flags"
+    )
+    parser.add_argument("-1", dest = "one_per_line", action = "store_true",help = "List one file per line") #dest sets the attribute name in parsed argument.
+    parser.add_argument("-a", "--all", action ="store_true",help = "Include directory entries whose names begin with a dot (.)")
+    parser.add_argument("dirs", nargs = "*", default = ["."], help = "Directories to list (default is current directory)")
+    return parser.parse_args()
+
+def print_directory_entries(path, one_per_line=False, show_all=False):
+    try:
+        # Retrieve all entries (files and subdirectories) inside the given path
+        directory_entries = os.listdir(path)
+    except FileNotFoundError:
+        # If the directory doesn't exist, print an error to stderr
+        print(f"ls: cannot access '{path}': No such file or directory", file=sys.stderr)
+        return
+    except PermissionError:
+        # If the directory exists but we don't have permission, print an error
+        print(f"ls: cannot open directory '{path}': Permission denied", file=sys.stderr)
+        return
+
+    # By default, ls hides "dotfiles" (names starting with ".").
+    # Only include them if the -a flag (show_all=True) is set.
+    if show_all:
+        directory_entries.extend([".",".."])
+    else:
+        #Filter out hidden files
+        directory_entries = [entry for entry in directory_entries if not entry.startwith(".")]
+    #output consistent with the default ls behavior.
+    directory_entries.sort()
+
+    if one_per_line:
+        # If -1 flag is set, print each entry on its own line
+        for entry_name in directory_entries:
+            print(entry_name)
+    else:
+        # Default behavior: print entries space-separated on one line
+        print("  ".join(directory_entries))
+
+def main():
+    args = parseargs()
+    # Loop through each directory provided
+    for directory in args.dirs:
+        print_directory_entries(
+            directory,
+            one_per_line = args.one_per_line,
+            show_all = args.all
+        )
+if __name__ == "__main__":
+    main()

implement-shell-tools/wc/wc.py

@@ -0,0 +1,82 @@
+import argparse
+import sys
+import glob # to find file paths and match patterns
+
+def parseargs():
+    parser = argparse.ArgumentParser(
+        prog = "wc",
+        description = "wc clone supporting -l, -w, -c flags"
+    )
+    parser.add_argument("-l", "--lines", action = "store_true",help = "print line counts")
+    parser.add_argument("-w", "--words", action ="store_true",help = "print word count")
+    parser.add_argument("-c", "--bytes", action ="store_true", help = "print byte count")
+    parser.add_argument("files", nargs="+", help="Files to read (shell globs allowed)")
+
+    return parser.parse_args()
+
+   #Uses glob to expand patterns like *.txt.
+def expand_files(patterns):
+    expanded = []
+    for p in patterns:
+        matches = glob.glob(p)
+        if matches:
+            expanded.extend(sorted(matches))  # predictable order
+        else:
+            print(f"wc: {p}: No such file", file=sys.stderr) #Prints an error if a pattern matches nothing.
+    return expanded
+
+def file_counts(filename):
+    try:
+        with open(filename, "rb") as f: #opening file in binary mode to be able to count bytes.
+            data = f.read()
+    except FileNotFoundError:
+        print(f"wc: {filename}: No such file", file=sys.stderr)
+        return None
+
+    text = data.decode("utf-8", errors="ignore")
+    line_count = text.count("\n")
+    word_count = len(text.split())
+    byte_count = len(data)
+
+    return line_count, word_count, byte_count
+
+def print_counts(filename, counts, show_lines, show_words, show_bytes): #args.lines is passed into the parameter show_lines and same for other arguments.
+    line_count, word_count, byte_count = counts
+
+    # If no flags are set, show all three
+    if not (show_lines or show_words or show_bytes):
+        print(f"{line_count:7} {word_count:7} {byte_count:7} {filename}")
+        return
+
+    output = []
+    if show_lines:
+        output.append(f"{line_count:7}") #:7 to ensure nums are rightaligned in a spaced column -just like GNU wc
+    if show_words:
+        output.append(f"{word_count:7}")
+    if show_bytes:
+        output.append(f"{byte_count:7}")
+    output.append(filename)
+    print(" ".join(output))
+
+def main():
+    args = parseargs()
+    files = expand_files(args.files)
+
+    total_lines, total_words, total_bytes = 0, 0, 0
+
+    for file in files:
+        counts = file_counts(file)
+        if counts is None:
+            continue
+        print_counts(file, counts, args.lines, args.words, args.bytes)
+        total_lines += counts[0]
+        total_words += counts[1]
+        total_bytes += counts[2]
+
+    # If multiple files, print totals
+    if len(files) > 1:
+        total_counts = (total_lines, total_words, total_bytes)
+        print_counts("total", total_counts, args.lines, args.words, args.bytes)
+
+if __name__ == "__main__":
+    main()