Lua - String gmatch() method

Quiz

string.gmatch() is a very useful string libraray function for pattern matching for multiple occurences of a string. string.gmatch() returns an iterator function. Everytime, we calls string.gmatch() function, it returns the next captured string based on the pattern provided.

Syntax

string.gmatch(s, pattern)

Where −

s − is the string to be searched in.
pattern − pattern to match. We can use specialized characters, quantifiers and capture groups in the pattern.

Returns

an iterator over the captures

Working of string.gmatch() function

string.gmatch() returns an iterator.
Every time, the iterator is called, it returns the next set of captured value using the pattern on the string.
If there is no captured string(using parenthesis), the entire matched word is returned.

Example - Usage of String.gmatch() function

In this example, we're printing words of a line.

main.lua

local data = "apple, banana, mango"

-- Iterate over all words and print each word on separate line
for word in string.gmatch(data, "%w+") do
  print(word)
end

Output

When we run the above program, we will get the following output−

apple
banana
mango

Example - Handing paired values

main.lua

local data = "name=Alice,age=30,city=NewYork"

-- Iterate over comma-separated value pairs
for key, value in string.gmatch(data, "(%w+)=(%w+)") do
  print("Key:", key, "Value:", value)
end

Output

When we run the above program, we will get the following output−

Key:    name    Value:  Alice
Key:    age     Value:  30
Key:    city    Value:  NewYork

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