It's just a sharper knife 🔪

knife is like the cut command, but delimits fields with whitespaces, any whitespaces.

Did you ever felt frustrated when trying to extract whitespace delimited fields using tools like cut? Should I split on tabs or spaces? How many?

$ echo "Mary   had a     little  lamb." | cut -f 2-4   
Mary   had a     little  lamb.
$ echo "Mary   had a     little  lamb." | cut -d' ' -f 2-4
  had

I created knife exactly for this purpose. It splits the input strings by whitespaces using Rust's std::str::SplitWhitespace and extracts fields specified using a pattern language like the one used by cut (e.g. 1,3,5-8 for the fields 1, 3, and 5 to 8 inclusively).

$ echo "Mary   had a     little  lamb." | knife 2-4   
had a little

That's it, it doesn't do anything more. If you need more customizable search or more bells and whistles, use dedicated tools like grep, sed, awk, etc or the cut itself.

Installation

To install it run:

cargo install --git https://github.com/twolodzko/knife.git

Benchmarks

knife runs in linear time. It is faster than cut in some common scenarios and slower or equal in others. It should perform roughly the same or better than cut.

$ hyperfine -N -r 10000 'echo "Mary had a little lamb." | cut -d" " -f 2-4' 'echo "Mary had a little lamb." | knife 2-4'
Benchmark 1: echo "Mary had a little lamb." | cut -d" " -f 2-4
  Time (mean ± σ):       1.7 ms ±   0.4 ms    [User: 1.0 ms, System: 0.6 ms]
  Range (min … max):     1.0 ms …   4.9 ms    10000 runs
 
Benchmark 2: echo "Mary had a little lamb." | knife 2-4
  Time (mean ± σ):       1.7 ms ±   0.5 ms    [User: 1.0 ms, System: 0.6 ms]
  Range (min … max):     1.0 ms …   4.5 ms    10000 runs
 
Summary
  echo "Mary had a little lamb." | knife 2-4 ran
    1.00 ± 0.38 times faster than echo "Mary had a little lamb." | cut -d" " -f 2-4

$ hyperfine -w 3 -N "cut -d' ' -f 2-10,50 IMDB\ Dataset.csv" "knife 2-10,50 IMDB\ Dataset.csv"
Benchmark 1: cut -d' ' -f 2-10,50 IMDB\ Dataset.csv
  Time (mean ± σ):     229.1 ms ±   1.1 ms    [User: 203.7 ms, System: 25.2 ms]
  Range (min … max):   227.4 ms … 231.4 ms    13 runs
 
Benchmark 2: knife 2-10,50 IMDB\ Dataset.csv
  Time (mean ± σ):     147.7 ms ±   1.7 ms    [User: 106.3 ms, System: 41.1 ms]
  Range (min … max):   146.0 ms … 152.3 ms    20 runs
 
Summary
  knife 2-10,50 IMDB\ Dataset.csv ran
    1.55 ± 0.02 times faster than cut -d' ' -f 2-10,50 IMDB\ Dataset.csv