Building Command-line Applications in Ruby

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Hector Castro Technical Evangelist at Basho @hectcastro

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Types of Command-line Interfaces

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$ # non-interactive example $

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$ # non-interactive example $ mv deal-with-it.gif ~/gifs $

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$ # interactive example $

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$ # interactive example $ ssh-keygen Generating public/private rsa key pair. Enter file in which to save the key (/Users/hector/.ssh/id_rsa):

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$ # interactive example $ ssh-keygen Generating public/private rsa key pair. Enter file in which to save the key (/Users/hector/.ssh/id_rsa): Created directory '/Users/hector/.ssh'. Enter passphrase (empty for no passphrase): Enter same passphrase again: Your identification has been saved in /Users/hector/.ssh/id_rsa. Your public key has been saved in /Users/hector/.ssh/id_rsa.pub.

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Checklist for a Non-interactive CLI

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$ # reduce interactivity and unnecessary output $

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$ # reduce interactivity and unnecessary output $ mv deal-with-it.gif ~/gifs $

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$ # emit accurate exit status $

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$ # emit accurate exit status $ mv deal-with-it.gif ~/gifs $

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$ # emit accurate exit status $ mv deal-with-it.gif ~/gifs $ echo $? 0 $

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$ # emit accurate exit status $

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$ # emit accurate exit status $ mv cats.gif ~/gifs mv: rename cats.gif to /Users/hector/gifs: No such file or directory $

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$ # emit accurate exit status $ mv cats.gif ~/gifs mv: rename cats.gif to /Users/hector/gifs: No such file or directory $ echo $? 1 $

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$ # have a concise name $

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$ # have a concise name $ svn co file:///does/anyone/use/me/anymore answer A answer/nope.txt Checked out revision 20. $

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$ # respect single and multi-letter options $

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$ # respect single and multi-letter options $ heroku -h << HELP CONTENT >> $

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$ # respect single and multi-letter options $ heroku -h << HELP CONTENT >> $ heroku --help << HELP CONTENT >>

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$ # ensure that you provide a --help option $

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$ # ensure that you provide a --help option $ dd -h dd: unknown operand -h $

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$ # ensure that you provide a --help option $ dd -h dd: unknown operand -h $ dd --help dd: unknown operand --help

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$ # use STDOUT correctly $

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$ # use STDOUT correctly $ curl https://api.github.com/users/hectcastro > hector.json

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$ # use STDOUT correctly $ curl https://api.github.com/users/hectcastro > hector.json $ cat hector.json | jq ".name" "Hector Castro"

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$ # use STDERR correctly $

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$ # use STDERR correctly $ curl joker://api.github.com/users/hectcastro curl: (1) Protocol joker not supported or disabled in libcurl

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$ # use STDERR correctly $ curl joker://api.github.com/users/hectcastro curl: (1) Protocol joker not supported or disabled in libcurl $ curl joker://api.github.com/users/hectcastro > error.txt 2>&1

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$ # use STDERR correctly $ curl joker://api.github.com/users/hectcastro curl: (1) Protocol joker not supported or disabled in libcurl $ curl joker://api.github.com/users/hectcastro > error.txt 2>&1 $ cat error.txt curl: (1) Protocol joker not supported or disabled in libcurl