CIT 383: Administrative Scripting Strings and Variables CIT 383: Administrative Scripting
CIT 383: Administrative Scripting Topics Single-quoted strings. Double-quoted strings. Choose your own quotes. Characters. String operators. CIT 383: Administrative Scripting
Single-quoted Strings Create strings using single quotes. ‘Hello ruby’ Escape ‘ using \ ‘O\’Reilly published Learning Ruby.’ ‘A \ is just itself in the middle.’ ‘This string ends with one backslash.\\’ ‘You can also have multi-line strings using \ to escape the newline character.’ CIT 383: Administrative Scripting
Double-quoted Strings Create strings using double quotes. “Hello Ruby” Double quoted strings have more escapes “Hello \”Rubyist\”” “A multi-\nline string.” “\tString indented by one tab.” “No need to use backslash to escape newlines in double quoted strings.” CIT 383: Administrative Scripting
CIT 383: Administrative Scripting String Escapes \f Form feed character (ASCII 12) \n Newline character (ASCII 10) \r Carriage return character (ASCII 13) \t Tab character (ASCII 9) \C-x Control-x character, i.e. \C-m is same as \r \nnn Byte represented by octal code from 000 to 377 \xnn Byte represented by hex code from 00 to FF \x The character x by itself, unless x is a newline or one of the special chars abcefnrstuvxCM01234567. Most commonly used to escape \, #, and “ CIT 383: Administrative Scripting
CIT 383: Administrative Scripting Interpolation Include result of code in double-quoted string “1 + 1 == #{1+1}” x = 2*3.1415926 “360 degrees == #{x} radians” CIT 383: Administrative Scripting
CIT 383: Administrative Scripting Choose your own Quotes If your string has a lot of ‘ or “ in it, you have to do a lot of escaping so ... Ruby allows you to choose your own quotes %q acts like single-quoted string %Q acts like double-quoted string Character after q or Q is the delimiter. Initial and final delimiters are identical unless you’re using one of a matched pair: (,[,{,< match ),],},> respectively. Examples %q(No need to worry about escaping ‘ here) %Q|Or for escaping “ in this string.| %Q|But you do have to escape \| here.| CIT 383: Administrative Scripting
CIT 383: Administrative Scripting Here Documents For long string literals, any chosen delimiter may be used within the string, so Ruby can delimit text using arbitrary strings like bash. document = <<HERE <html><head> <title>Here Document!</title> </head><body> “A quoted body isn’t normal.” </body></html> HERE CIT 383: Administrative Scripting
CIT 383: Administrative Scripting Here Documents Behave like double-quoted strings String interpolation Escape characters Single-quoted here documents: document = <<‘EOD’ You can use #{1+1} to escape ruby code, and you can use \t as backslash and t, as they don’t do anything special here. EOD CIT 383: Administrative Scripting
CIT 383: Administrative Scripting Character Literals Single characters denoted by a ? prefix ?a is the character a ?” is the double-quote character ?\t is the tab character Not the same as a single character string ?a != ‘a’ CIT 383: Administrative Scripting
CIT 383: Administrative Scripting String Operators Concatenation “Hello” + “ “ + “Ruby” == “Hello Ruby” Converting numbers to strings version = 1.9 “Hello Ruby “ + version.to_s == “Hello Ruby 1.9” “Hello Ruby #{version}” Multiplication ellipsis = ‘.’*3 # Evaluates to ... CIT 383: Administrative Scripting
CIT 383: Administrative Scripting Logical Operators Equality ‘Hello’ == ‘Hello’ Inequality ‘Hello’ != ‘hello’ Less Than ‘a’ <= ‘b’ Less Than or Equal To ‘a’ <= ‘a’ Greater Than ‘baz’ > ‘bar’ Greater Than or Equal To ‘baz’ >= ‘baz’ CIT 383: Administrative Scripting
CIT 383: Administrative Scripting Accessing Characters Use index to access individual characters x = “Hello” x[0] == ?H x[1] == ?e Negative numbers index from the end x[-1] == ?o x[-2] == ?l Use index to modify string, -1 index special x[0] = ?M # changes x to Mello x[-1] = “” # changes to Mell CIT 383: Administrative Scripting
CIT 383: Administrative Scripting Substrings Use double index to access substrings x = “Hello” x[0,2] == “He” x[-2,2] == “lo” x[0,0] == “” # For all strings x[0,10] == “Hello” x[0,-1] == nil # Negative lens ret nil Modify string by assigning to index x[0,2] = “Ma” x[-2,2] = “ow” x == “Mallow” x[2,2] = “” x == “Maow” CIT 383: Administrative Scripting
CIT 383: Administrative Scripting References Michael Fitzgerald, Learning Ruby, O’Reilly, 2008. David Flanagan and Yukihiro Matsumoto, The Ruby Programming Language, O’Reilly, 2008. Hal Fulton, The Ruby Way, 2nd edition, Addison-Wesley, 2007. Dave Thomas with Chad Fowler and Andy Hunt, Programming Ruby, 2nd edition, Pragmatic Programmers, 2005. CIT 383: Administrative Scripting