silverbullet/website/API/string.md

API docs for Lua's string module.

string.byte(s, i?, j?)

Returns the numeric codes of characters in string s from position i to j. If j is not provided, defaults to i.

Example:

print(string.byte("Hello", 1))  -- prints: 72 (ASCII code for 'H')

string.char(...)

Returns a string from given ASCII codes.

Example:

print(string.char(72))  -- prints: H

string.find(s, pattern, init?, plain?)

Looks for the first match of pattern in string s. Returns start and end indices of match.

Example:

local start, end_ = string.find("Hello", "l")
print(start)  -- prints: 3 (first 'l' position)

string.gsub(s, pattern, repl, n?)

Returns a copy of s in which all (or the first n) occurrences of pattern have been replaced by repl.

Example:

-- Simple string replacement
local result, count = string.gsub("hello world", "hello", "hi")
print(result, count)  -- prints: hi world 1

-- Multiple replacements with limit
result = string.gsub("hello hello hello", "hello", "hi", 2)
print(result)  -- prints: hi hi hello

-- Function replacement
result = string.gsub("hello world", "(h)ello", function(h)
    return string.upper(h) .. "i"
end)
print(result)  -- prints: Hi world

-- Pattern with magic characters
result = string.gsub("hello.world", "%.", "-")
print(result)  -- prints: hello-world

string.match(s, pattern, init?)

Returns the captures from the first match of pattern in string s.

Example:

-- Basic pattern matching
print(string.match("hello", "h"))  -- prints: h

-- Multiple captures
local day, month, year = string.match("2024-03-14", "(%d+)-(%d+)-(%d+)")
print(day, month, year)  -- prints: 2024 03 14

-- With init position
print(string.match("hello world", "(world)", 7))  -- prints: world

-- Pattern characters
print(string.match("123", "%d+"))      -- prints: 123
print(string.match("abc123", "%a+"))   -- prints: abc
print(string.match("   abc", "%s+"))   -- prints: "   "

string.gmatch(s, pattern)

Returns an iterator function that returns successive captures from pattern matches in string s.

Example:

local words = {}
for word in string.gmatch("hello world lua", "%w+") do
    table.insert(words, word)
end
print(words[1], words[2], words[3])  -- prints: hello world lua

string.len(s)

Returns the length of string s.

Example:

print(string.len("Hello"))  -- prints: 5

string.lower(s)

Returns a copy of s with all characters converted to lowercase.

Example:

print(string.lower("Hello"))  -- prints: hello

string.upper(s)

Returns a copy of s with all characters converted to uppercase.

Example:

print(string.upper("Hello"))  -- prints: HELLO

string.rep(s, n, sep?)

Returns a string that is the concatenation of n copies of string s.

Example:

print(string.rep("Hello", 3))  -- prints: HelloHelloHello

string.reverse(s)

Returns a string with the characters of s in reverse order.

Example:

print(string.reverse("hello"))  -- prints: olleh
print(string.reverse(""))       -- prints: "" (empty string)

string.sub(s, i, j?)

Returns the substring of s from position i to j.

Example:

print(string.sub("Hello", 2, 4))  -- prints: ell

string.split(s, sep)

Splits string s using separator sep and returns a table of substrings.

Example:

local parts = string.split("a,b,c", ",")
for i, part in ipairs(parts) do
    print(part)
end
-- Output:
-- a
-- b
-- c

Non-standard Extensions

string.startswith(s, prefix)

Returns true if string s starts with prefix.

Example:

print(string.startswith("hello world", "hello"))  -- prints: true
print(string.startswith("hello world", "world"))  -- prints: false

string.endswith(s, suffix)

Returns true if string s ends with suffix.

Example:

print(string.endswith("hello world", "world"))  -- prints: true
print(string.endswith("hello world", "hello"))  -- prints: false