Ruby - Built-in Functions

Since the Kernel module is included by Object class, its methods are available everywhere in the Ruby program. They can be called without a receiver (functional form). Therefore, they are often called functions.

Functions for Numbers

Here is a list of Built-in Functions related to number. They should be used as follows −


num = 12.40
puts num.floor      # 12
puts num + 10       # 22.40
puts num.integer?   # false  as num is a float.

This will produce the following result −


Functions for Float

Functions for Math

Conversion Field Specifier

The function sprintf( fmt[, arg...]) and format( fmt[, arg...]) returns a string in which arg is formatted according to fmt. Formatting specifications are essentially the same as those for sprintf in the C programming language. Conversion specifiers (% followed by conversion field specifier) in fmt are replaced by formatted string of corresponding argument.

Following is the usage example −


str = sprintf("%s\n", "abc")   # => "abc\n" (simplest form)
puts str 

str = sprintf("d=%d", 42)      # => "d=42" (decimal output)
puts str 

str = sprintf("%04x", 255)     # => "00ff" (width 4, zero padded)
puts str 

str = sprintf("%8s", "hello")  # => " hello" (space padded)
puts str 

str = sprintf("%.2s", "hello") # => "he" (trimmed by precision)
puts str 

This will produce the following result −

d = 42

Test Function Arguments

The function test( test, f1[, f2]) performs one of the following file tests specified by the character test. In order to improve readability, you should use File class methods (for example, File::readable?) rather than this function.

Following is the usage example. Assuming main.rb exist with read, write and not execute permissions −


puts test(?r, "main.rb" )   # => true
puts test(?w, "main.rb" )   # => true
puts test(?x, "main.rb" )   # => false

This will produce the following result −