Reference

String Methods

Methods for string manipulation.

1. string.byte

   Return the numeric byte codes of a Lua 5.4 string. Supports negative indices and returns one integer per byte in the range.

   string.byte(s [, i [, j]])
2. string.char

   string.char in Lua 5.4 takes zero or more integers and returns a string whose bytes are those integer codes. Inverse of string.byte for raw byte sequences.

   string.char (...)
3. string.dump

   `string.dump` serializes a Lua function to a binary chunk string that `load()` can rebuild for fast startup, bytecode caching, and shipping precompiled code.

   string.dump (function [, strip])
4. string.find

   string.find searches a Lua string for a pattern match, returning start and end positions. Supports plain literal search to bypass pattern syntax.

   string.find(s, pattern [, init [, plain]])
5. string.format()

   string.format() in Lua 5.4 substitutes printf-style %-directives into a string — covers flags, width, precision, specifiers, examples, and pitfalls.

   string.format(fstr, ...)
6. string.gmatch

   string.gmatch returns an iterator that yields every non-overlapping match of a Lua pattern, in order, with captures unpacked for for-in loops.

   string.gmatch(s, pattern [, init])
7. string.gsub

   string.gsub substitutes pattern matches in Lua strings, returns transformed string and count. Supports string, table, and function replacements.

   string.gsub(s, pattern, repl [, n])
8. string.len

   string.len returns the byte length of a Lua 5.4 string. Equivalent to the # operator, it counts embedded NUL bytes and is the canonical way to size a string.

   string.len(s)
9. string.lower

   string.lower returns a copy of a string with all ASCII uppercase letters replaced by their lowercase equivalents. Locale-driven; not UTF-8 aware.

   string.lower(s)
10. string.match

    string.match returns the captures from the first match of a Lua pattern in a string, or the whole match when no captures are defined.

    string.match(s, pattern [, init])
11. string.pack

    Pack Lua values into a binary string with a format string. Lua 5.4 string.pack reference: every option, alignment rules, and worked examples.

    string.pack(fmt, v1, v2, ...)
12. string.packsize

    string.packsize returns the byte length that string.pack would produce for a given format string, without packing any values or allocating a buffer.

    string.packsize(fmt)
13. string.rep

    string.rep returns a string made of n copies of s, optionally joined by sep, or an empty string when n is not positive.

    string.rep(s, n [, sep])
14. string.reverse

    Return a copy of a string with its bytes in reverse order. Covers palindrome checks, UTF-8 caveats, and method syntax.

    string.reverse(s)
15. string.sub

    string.sub returns a substring of a Lua 5.4 string by 1-based inclusive byte indices, with negative indices counting back from the end.

    string.sub(s, i [, j])
16. string.unpack

    string.unpack reads a binary string produced by string.pack and decodes it into Lua values, with optional start position and a trailing offset for streaming.

    string.unpack(fmt, s [, pos])
17. string.upper

    string.upper returns a copy of a string with all ASCII lowercase letters replaced by their uppercase equivalents. Locale-driven; not UTF-8 aware.

    string.upper(s)