Shell Speedup

https://work.lisk.in/2020/11/20/even-faster-bash-startup.html#completions

https://danpker.com/posts/faster-bash-startup/

Benchmark bash startup speed by hyperfine

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hyperfine 'bash -i'

Benchmark 1: bash -i Time (mean ± σ): 262.5 ms ± 29.4 ms [User: 156.9 ms, System: 74.1 ms] Range (min … max): 249.0 ms … 345.9 ms 10 runs

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$ source ~/.bash_profile 
bash_exports: 0.015
bash_aliases: 0.000
bash_autocompletion: 0.000
bash_colors: 0.000
bash_functions: 0.000
bash_options: 0.000
bash_prompt: 0.024
bash.local: 0.000
conda: 0.000

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Benchmark 1: bash --login
  Time (mean ± σ):      45.8 ms ±   2.0 ms    [User: 16.3 ms, System: 20.7 ms]
  Range (min … max):    42.0 ms …  52.8 ms    57 runs

eval $(/opt/homebrew/bin/brew shellenv) would add ~ 27 ms delay

bash_prompt add ~ 20 ms

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bash_exports: 0.001 s
bash_aliases: 0.000 s
bash_autocompletion: 0.029 s
bash_colors: 0.000 s
bash_functions: 0.000 s
bash_options: 0.000 s
bash_prompt: 0.022 s
bash.local: 0.000 s
conda: 0.003

Autocompletion diff: 140 ms on load up

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myMacbook:~ wyq977$ hyperfine 'bash --login'
Benchmark 1: bash --login
  Time (mean ± σ):      12.9 ms ±   0.8 ms    [User: 5.0 ms, System: 4.9 ms]
  Range (min … max):    11.7 ms …  16.8 ms    187 runs
 
myMacbook:~ wyq977$ hyperfine 'bash -i'
Benchmark 1: bash -i
  Time (mean ± σ):     160.2 ms ±   2.4 ms    [User: 120.7 ms, System: 33.2 ms]
  Range (min … max):   157.3 ms … 164.9 ms    17 runs

ZSH is much faster?

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myMacbook:~ wyq977$ hyperfine 'zsh --login'
Benchmark 1: zsh --login
  Time (mean ± σ):       4.4 ms ±   0.6 ms    [User: 1.3 ms, System: 1.8 ms]
  Range (min … max):     3.2 ms …   7.2 ms    311 runs


❯ hyperfine 'zsh -cli exit'
Benchmark 1: zsh -cli exit
  Time (mean ± σ):      72.8 ms ±   1.5 ms    [User: 26.2 ms, System: 30.2 ms]
  Range (min … max):    69.7 ms …  76.5 ms    39 runs
 
❯ hyperfine '/opt/homebrew/bin/bash -cli exit'
Benchmark 1: /opt/homebrew/bin/bash -cli exit
  Time (mean ± σ):      77.0 ms ±   3.4 ms    [User: 37.4 ms, System: 27.3 ms]
  Range (min … max):    73.9 ms …  93.6 ms    31 runs
 