string.find()
The string.find() function searches for a pattern within a string and returns the starting and ending indices of the first match. It is commonly used for pattern matching or substring searching.
Syntax
string.find(s, pattern, init, plain)
Parameters
- Name
s- Type
- string
- Description
The string to search within.
- Name
pattern- Type
- string
- Description
The pattern to search for. This can be a plain string or a Lua pattern.
- Name
init- Type
- number
- Description
The starting position for the search. Defaults to
1. Negative values count from the end of the string.
- Name
plain- Type
- boolean
- Description
If
true, disables pattern matching and treats thepatternas a plain string. Defaults tofalse.
Return Value
- If a match is found: Returns the start and end indices of the first occurrence of the pattern, and any captured substrings (if applicable).
- If no match is found: Returns
nil.
Examples
Example 1: Basic search
Search for a substring in a string.
Example 1
local text = "The quick brown fox"
local startIndex, endIndex = string.find(text, "quick")
print(startIndex, endIndex)
-- Output: 5 9
Example 2: Using patterns
Search for the first word starting with a vowel.
Example 2
local text = "The quick brown fox"
local startIndex, endIndex = string.find(text, "%a*[aeiou]%a*")
print(startIndex, endIndex)
-- Output: 5 9 (matches "quick")
Example 3: Starting position (init)
Specify where the search begins.
Example 3
local text = "The quick brown fox jumps"
local startIndex, endIndex = string.find(text, "fox", 11)
print(startIndex, endIndex)
-- Output: 17 19
Example 4: Plain search
Disable pattern matching with plain.
Example 4
local text = "The quick [pattern] fox"
local startIndex, endIndex = string.find(text, "[pattern]", 1, true)
print(startIndex, endIndex)
-- Output: 11 19
Example 5: No match
Handle cases where the pattern is not found.
Example 5
local text = "The quick brown fox"
local result = string.find(text, "cat")
print(result)
-- Output: nil
Use Cases
- Substring Search: Find specific words or characters in a string.
- Pattern Matching: Use Lua patterns to identify substrings that match specific criteria.
- Custom Search: Limit the search range with
initor perform literal matches withplain.
See also
string.match(): Extracts the first substring that matches a pattern.string.gmatch(): Iterates over all substrings in a string that match a pattern.string.gsub(): Replaces all occurrences of a pattern in a string with a replacement string.string.sub(): Extracts a substring using start and end indices.