How to Work with Strings in Ruby

March 12, 2026 · 3 min read · Updated March 13, 2026 · beginner

ruby strings guide

Ruby strings are incredibly versatile objects. Whether you’re cleaning user input, parsing file contents, or building dynamic URLs, you’ll constantly work with text. This cookbook gives you practical recipes for common string operations.

Trimming Whitespace

White space at the edges of strings often comes from user input or file processing. Ruby gives you several methods to handle it.

Basic Trimming

The strip method removes leading and trailing whitespace:

name = "  John Doe  "
name.strip  # => "John Doe"

Use lstrip to remove only leading whitespace, and rstrip for trailing:

"  hello".lstrip  # => "hello"
"hello  ".rstrip  # => "hello"

These methods return new strings. Use the bang versions (strip!, etc.) to modify in place.

Removing Specific Characters

The chomp method removes trailing newlines or a specified suffix:

"hello\n".chomp      # => "hello"
"hello\r\n".chomp    # => "hello"
"hello.".chomp(".")  # => "hello"

The chop method removes the last character regardless of what it is:

"hello!".chop  # => "hello"

Case Conversion

Converting string case is essential for normalization and display.

Uppercase and Lowercase

"hello".upcase    # => "HELLO"
"HELLO".downcase  # => "hello"

Capitalize and Swap

The capitalize method makes the first character uppercase and the rest lowercase:

"hello WORLD".capitalize  # => "Hello world"

The swapcase method swaps uppercase to lowercase and vice versa:

"Hello World".swapcase  # => "hELLO wORLD"

Searching and Replacing

Checking for Substrings

Use include? to check if a string contains a substring:

"hello world".include?("world")  # => true
"hello".include?("xyz")          # => false

Simple Replacement with `sub` and `gsub`

The sub method replaces the first occurrence:

"hello world".sub("world", "ruby")  # => "hello ruby"

The gsub method replaces all occurrences:

"one one one".gsub("one", "1")  # => "1 1 1"

Both methods support regex:

"hello 123 world".gsub(/\d+/, "NUM")  # => "hello NUM world"

Pattern Matching

The match method returns a MatchData object:

result = "price: $49.99".match(/\$\d+\.\d+/)
result[0]  # => "$49.99"

For simple checks, use =~ (returns index) or match? (returns boolean):

"hello" =~ /ell/    # => 1
"hello".match?(/xyz/)  # => false

Splitting and Joining

Splitting Strings

The split method breaks a string into an array:

"one,two,three".split(",")  # => ["one", "two", "three"]

Split on whitespace automatically:

"hello world".split  # => ["hello", "world"]

Limit the number of splits with the second argument:

"a,b,c,d".split(",", 2)  # => ["a", "b,c,d"]

Character and Line Splitting

The chars method returns an array of characters:

"hello".chars  # => ["h", "e", "l", "l", "o"]

The lines method splits on newlines:

"line1\nline2\nline3".lines  # => ["line1\n", "line2\n", "line3"]

Joining Arrays

The inverse of split is join:

["a", "b", "c"].join("-")  # => "a-b-c"
["hello", "world"].join(" ")  # => "hello world"

String Interpolation

Basic Interpolation

Ruby string interpolation evaluates expressions inside #{}:

name = "Alice"
"Hello, #{name}!"  # => "Hello, Alice!"

Alternative Delimiters

For strings containing many quotes, use alternative delimiters:

%Q(He said: "Hello")     # Double-quoted
%q(He said: 'Hello')     # Single-quoted (no interpolation)

The %w shortcut creates word arrays:

%w[apple banana cherry]  # => ["apple", "banana", "cherry"]

Encoding Considerations

Ruby 3+ handles encoding carefully. Most strings default to UTF-8.

Checking Encoding

"hello".encoding        # => #<Encoding:UTF-8>

Force Encoding

If you have encoding issues, force it:

str = "\xC3\xA9".force_encoding("UTF-8")

Valid Encoding

Check if a string is valid UTF-8:

"hello".valid_encoding?  # => true

Practical Examples

Slugifying a String

Create URL-friendly slugs:

def slugify(text)
  text.downcase
      .strip
      .gsub(/[^\w\s-]/, "")
      .gsub(/\s+/, "-")
end

slugify("Hello World!")  # => "hello-world"

Truncating Text

Add ellipsis to long strings:

def truncate(text, length = 100)
  return text if text.length <= length
  text[0...length].strip + "..."
end

truncate("This is a long string...", 10)  # => "This is a..."