Reading from linux command line with Python

Question

Is there a way to read data that is coming into the command-line, straight into another Python script for execution?

Answer 1

Here is an example for future reference and also help others.
Tested with Python 2.6, 2.7, 3.6

# coding=utf-8
"""
Read output from command line passed through a linux pipe
$ vmstat 1 | python read_cmd_output.py 10 3 10
This will warn when the column value breached the threshold for N time consecutively
"""

import sys
import re

def main():
    """ Main """
    values = []
    try:
        column, occurrence, threshold = sys.argv[1:]
        column = int(column)
        occurrence = int(occurrence)
        threshold = int(threshold)
    except ValueError:
        print('Usage: {0}   '.format(sys.argv[0]))
        sys.exit(1)

    with sys.stdin:
        for line in iter(sys.stdin.readline, b''):
            line = line.strip()
            if re.match(r'\d', line):
                elems = re.split(r'\s+', line)
                values.append(elems[column-1])
                len(values) > occurrence and values.pop(0)
                nb_greater = len([x for x in values if int(x) > threshold])
                print(values, nb_greater, 'Warn' if nb_greater >= len(values) else '')

if __name__ == '__main__':
    try:
        main()
    except KeyboardInterrupt:
        print("\nUser interrupted the script")
        sys.exit(1)