Rust で tail コマンドを実装してみた ref: https://qiita.com/17g/items/e4bc81e5c2c8428858a7

file0.txt

$ cargo -V
cargo 0.24.0 (45043115c 2017-12-05)
$ rustc -V
rustc 1.23.0 (766bd11c8 2018-01-01)

file1.txt

Usage: rtail [options] FILE

Options:
    -n NUMS             number of lines
    -h                  print help

file2.txt

$ time tail -n 10000 120000.log
tail -n 10000 120000.log  0.06s user 0.02s system 30% cpu 0.251 total

file3.txt

$ time ./target/debug/rtail -n 10000 120000.log
./target/debug/rtail -n 10000 120000.log  0.63s user 1.15s system 90% cpu 1.979 total

file4.txt

$ time ./target/release/rtail -n 10000 120000.log
./target/release/rtail -n 10000 120000.log  0.26s user 1.14s system 87% cpu 1.591 total

file5.txt

$ time ./target/debug/rtail -n 10000 120000.log
./target/debug/rtail -n 10000 120000.log  0.09s user 0.01s system 70% cpu 0.132 total

file6.txt

$ time ./target/release/rtail -n 10000 120000.log
./target/release/rtail -n 10000 120000.log  0.00s user 0.01s system 7% cpu 0.205 total