Regex cheatsheet. Many programs use regular expression to find & replace text. However, they tend to come with their own different flavor. You can probably expect most modern software and programming languages to be using some variation of the Perl flavor, 'PCRE'; however command-line tools (grep, less.) will often use the POSIX flavor (sometimes with an extended variant, e.g. Ruby Date Format (strftime) cheat sheet of all shortcuts and commands. OverAPI.com is a site collecting all the cheatsheets,all!
- PDF Link: cheatsheet-ruby-A4.pdf, Category: languages
- Blog URL: https://cheatsheet.dennyzhang.com/cheatsheet-ruby-A4
- Related posts: Golang CheatSheet, Python CheatSheet, #denny-cheatsheets
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1.1 Summary
| Name | Comment |
|---|
| Check syntax | ruby -c my.rb |
| Generate random key | r = Random.new, r.rand(10...42) |
| Install ruby 2.4 | GitHub: Ubuntu install ruby 2.4 |
| Install package with specific version | gem install rubocop -v '0.44.1' |
| Install package with a range of versions | gem install rails -v '~>4.0.0' |
| Install package with a range of versions | gem install rails -v '>3.1, <4.1' |
| Get RubyGem env | gem env |
| Check whether variable is nil | if value.nil? |
| Run system command | system('commandhere') |
| Run bash command | stdin, stdout, stderr = Open3.popen3('ls .') |
1.2 List
| Name | Comment |
|---|
| Check existence | [‘Cat’, ‘Dog’, ‘Bird’].include? ‘Dog’ |
| Find item | l1.find_index(x) |
| Remove item from list | l1.delete_at(2) |
| Remove duplicate entries | [1,2,2,1,4,4,5,6,7,8,5,6].uniq |
| Deep copy a list | l1=l.dup |
1.3 String
| Name | Comment |
|---|
| Substring | string[1..3] |
| Search substring | “option=name=bob”.index(“name”) |
| Replace | “Welcome to PHP Essentials!”.gsub(“PHP”, “Ruby”) |
| Remove trailing comma | “ab;123;”.chomp(“;”) |
| Strip whitespace | host = host.strip() |
1.4 Integer
1.5 Conversion
| Name | Comment |
|---|
| Convert string to int | “14”.toi, “1,112”.delete(‘,’).toi |
| Round float to 2 digits | (5.65235534).round(2) |
| Format datetime | puts time.strftime('%Y-%m-%d %H:%M:%S') |
1.6 Dict & Set
1.7 File
| Name | Comment |
|---|
| Check whether directory exist | File.directory?('xxx') |
| Check whether files exist | File.file?('hello.rb') |
| Read file to string | contents = File.read('filename') |
1.8 Code Snippets
Ruby Strftime Cheat Sheet
1.9 More Resources