This is a python implementation of the Unix grep command.
Written during Hacker School, Batch[4], Fall 2012.
python mygrep.py [--help] [--color] [-h] [-i] [-l] [-n] [-R]
pattern [FILES [FILES ...]]
Find matches of a pattern in lines of file(s).
positional arguments:
pattern the pattern to find
FILES the files(s) to search
optional arguments:
--help show this help message and exit
--color, --colour highlight matches
-h, --no-filename print without filename headers
-i, --ignore-case case-insensitive search
-l, --files-with-matches print only filenames with matches
-n, --line-number print line numbers, indexed from 1
-R, -r, --recursive recursively search directories
If called with no file arguments, reads from standard input and follows grep's behavior when reading from standard input. Can also be used with pipes.
As an exercise in optimazation, I looked into string searching algorithms to make mygrep faster. I decided to go with Boyer-Moore because that's what GNU's grep is based on. I worked on a separate mini-version of mygrep for testing:
python search_test.py [--help] [--color] [-R] [-b] pattern [FILES [FILES ...]]
Find occurrences of a pattern in lines of file(s).
positional arguments:
pattern the pattern to find
FILES the files(s) to search
optional arguments:
--help show this help message and exit
--color, --colour highlight pattern in output
-R, -r, --recursive recursively search directories
-b, --boyer-moore search with boyer-moore algorithm
Using naive search python search_test.py King bible.txt:
real 0m2.173s
user 0m2.144s
sys 0m0.024s
Using Boyer_Moore search python search_test.py King bible.txt -b, you can see it's a little faster:
real 0m1.732s
user 0m1.705s
sys 0m0.023s
But not nearly as fast as regular grep grep King bible.txt:
real 0m0.200s
user 0m0.196s
sys 0m0.004s
- BSD grep man page
- Why GNU grep is fast
- Boyer-Moore string search algorithm explanation
- visualizer for Boyer Moore's bad char heuristic
- python argparse module
##Todo/Extension Ideas
- use boyer-moore in mygrep.py
- figure out if output can handle colors, when piping or writing results to a file.