Python cut.py

import argparse import sys

def cut(fields, delimiter, input_file):

   """
   Extract specified fields or columns from the input file or standard input.

   :param fields: Comma-separated list of fields to extract (1-based indexing).
   :param delimiter: Delimiter used to separate fields.
   :param input_file: Input file path or None for standard input.
   """
   # Parse the fields to extract
   try:
       field_indices = [int(f) - 1 for f in fields.split(",")]
   except ValueError:
       print("Error: Fields must be integers.", file=sys.stderr)
       sys.exit(1)

   # Open the input file or use standard input
   input_source = open(input_file, "r") if input_file else sys.stdin

   try:
       for line in input_source:
           # Split the line using the specified delimiter
           parts = line.rstrip().split(delimiter)

           # Extract the specified fields and print them
           try:
               output = delimiter.join([parts[i] for i in field_indices])
               print(output)
           except IndexError:
               print("Error: Field index out of range.", file=sys.stderr)
   finally:
       if input_file:
           input_source.close()

def main():

   parser = argparse.ArgumentParser(description="Python implementation of the cut command.")
   parser.add_argument("-f", "--fields", required=True, help="Comma-separated list of fields to extract (1-based indexing).")
   parser.add_argument("-d", "--delimiter", default="\t", help="Delimiter used to separate fields (default: tab).")
   parser.add_argument("-i", "--input", help="Input file path (default: standard input).")

   args = parser.parse_args()

   cut(fields=args.fields, delimiter=args.delimiter, input_file=args.input)

if __name__ == "__main__":

   main()