string
The string library provides generic functions to manipulate strings, such as to extract substrings or match patterns. You can access the string library by the global string library.
See String Pattern Reference for details on using string.match() and string.gmatch() to find a piece, or substring, of a longer string.
Tóm Tắt
Chức Năng
Returns the internal numerical codes of the characters s[i], s[i+1], ..., s[j]. The default value for i is 1; the default value for j is i. These indices are corrected following the same rules of function string.sub.
Receives zero or more integers and returns a string with length equal to the number of arguments, in which each character has the internal numerical code equal to its corresponding argument.
Looks for the first match of pattern in the string s and returns the indices of s where the occurrence starts and ends.
Returns a formatted version of its variable number of arguments following the description given in its first argument, which must be a string.
Returns an iterator function that returns the next captures from pattern over the string s each time it's called.
Returns a copy of s in which all or the first n occurrences of the pattern are replaced with the given replacement. The second value returned is the total number of substitutions made.
Returns the length of a string.
Returns a copy of a string with all uppercase letters changed to lowercase.
Looks for the first match of pattern in the string s. If a match is found, it is returned; otherwise, it returns nil. A third, optional numerical argument, init, specifies where to start the search.
Returns a binary string containing the provided arguments.
Returns the size in bytes of any string packed with a given description.
Returns a string that is the concatenation of n copies of the string s.
Returns a string that is the string s reversed.
Splits a string into parts based on the defined separator character(s), returning a table of ordered results.
Returns the substring of s that starts at i and continues until and including j. i and j can be negative. i defaults to 1 and j defaults to -1.
Extracts the values packed in the provided binary string.
Returns a copy of a string with all lowercase letters changed to uppercase.
Chức Năng
byte
Returns the internal numerical codes of the characters s[i], s[i+1], ..., s[j]. The default value for i is 1; the default value for j is i. These indices are corrected following the same rules of function string.sub().
Lợi Nhuận
find
Searches for the first occurrence of a pattern in a string and returns the start and end indices of the match. If no match is found, it returns nil. You can specify where to start the search using the optional init parameter which defaults to 1 and can be negative. An optional plain parameter turns off pattern matching, so the function performs a plain substring search; note that if you use plain, you must also provide init.
-- Example 1: Basic usagelocal s = "Hello, world!"local pattern = "world"local start_index, end_index = string.find(s, pattern)print(start_index, end_index) -- Output: 8 12
-- Example 2: Using init parameterlocal s = "Hello, world! Hello, Roblox!"local pattern = "Hello"local start_index, end_index = string.find(s, pattern, 10)print(start_index, end_index) -- Output: 15 19
-- Example 3: Using plain parameterlocal s = "Hello, world! (Hello)"local pattern = "(Hello)"local start_index, end_index = string.find(s, pattern, 1, true)print(start_index, end_index) -- Output: 14 20
-- Example 4: No Pattern foundlocal s = "Hello, world!"local pattern = "Roblox"local start_index, end_index = string.find(s, pattern)print(start_index, end_index) -- Output: nil
Tham Số
format
Returns a formatted version of its variable number of arguments following the description given in its first argument, which must be a string.
You can convert variables into user-friendly strings of text using the string.format() function. The function requires the following format:
%[flags][width].[precision][specifier].
Specifiers
The most important part of string formatting is the specifiers.
Specifier | Accepts | Outputs | Example Output |
---|---|---|---|
c | integer | 3 | |
d or i | integer | Decimal representation. | 321 |
e or E | float | Scientific notation using e or E. | 3.296e2 3.296E2 |
f | float | 3231.1231 | |
g or G | float | The shorter of e/E and f. | 3E14 3e14 |
o | integer | Octal representation. | 610 |
q | string | String in a form suitable to be safely read back by the Lua interpreter. The string is written between double quotes and all double quotes, new lines, embedded zeros, and backslashes are correctly escaped. | "print(\"Hi\")" |
s | string | Hello world! | |
u | integer | Decimal representation. | 3131 |
x or X | integer | Hexadecimal representation. | 7fa 7FA |
* | any | Equivalent to s but accepts any variable by converting it to a string using tostring(). | table: 0x0123456789abcdef |
% | % followed by another % will return the % sign itself. | % |
local str = "The magic word is %s"print(string.format(str, "Roblox"))-- The magic word is Robloxlocal str = "The magic word is %q"print(string.format(str, "Roblox"))-- The magic word is "Roblox"local str = "Skip to \na new line and \nanother new line!"print(string.format(str, "%q"))--[[ Output:Skip toa new line andanother new line!]]
Flags
Flag | Description |
---|---|
- | Left-justify the given field width (see Width below). Right justification is the default. |
+ | Forces a "+" sign to precede a number. Has no effect on negative numbers. |
(space) | One blank space is inserted before a positive number, while negative numbers are unaffected. This is useful for making positive and negative numbers vertically align in a visual stacked list. |
# | When used with o and x/X, writes a 0 (octal) or 0x/0X (hex) before values other than zero. When used with e/E and f, forces the output to contain a decimal point, even if no digits would follow (by default, no decimal point is written if no digits follow). When used with g or G, the result is the same as with e or E but trailing zeros are not removed. |
0 | Left-pads the number with zeros instead of empty spaces (see Width below). |
local str = "%-10d"print(string.format(str, 300) .. "]")-- 300 ]-- There are 7 spaces between '300' and ']'local str = "%+i versus %+i"print(string.format(str, 300, -300)) -- +300 versus -300local str = "There is a% i%% chance of rain in Seattle today."print(string.format(str, 100))-- There is a 100% chance of rain in Seattle today.
Width
Width | Description |
---|---|
(number) | Minimum number of characters to return. If the number of characters to be formatted is less than this number, the result is padded with blank spaces. |
local str = "%012i"print("Score: " .. string.format(str, 15000))-- Output: Score: 000000015000-- The output has 12 digits total, left-padded with zeros
Precision
The default precision is 1. If you give a period without a value, the default is 0.
Precision | Description |
---|---|
.(number) | For integer specifiers (d, i, o, u, x/X), precision specifies the minimum number of digits to be returned. If the value to be formatted is shorter than this number, the result is padded with leading zeros. A precision of 0 means that no character is written for the value 0. For e/E and f specifiers, this is the number of digits to be printed after the decimal point. For g/G specifiers, this is the maximum number of digits (before the e/E, if present). For s, this is the maximum number of characters to be returned. For c and q, this has no effect. |
-- Add decimal with precision of 2 for a currency outputlocal str = "$%.2f"print(string.format(str, 300)) -- Output: $300.00-- Return first 6 letters of a stringlocal str = "%.6s"print(string.format(str, "Robloxian")) -- Output: Robloxlocal str = "Once upon a time, there was a dragon named %s and it had %.8f horns."print(string.format(str, "Pi", math.pi))-- Output: Once upon a time, there was a dragon named Pi and it had 3.14159265 horns.
Lợi Nhuận
gsub
Short for global substitution. Returns a copy of s in which all (or the first n, if given) occurrences of the pattern are substituted (replaced) with the given replacement. The second value returned is the total number of substitutions made.
The replacement can be one of several types, each used differently to determine the actual string:
- string: The pattern is replaced with the string directly
- table: The string that matched the pattern is looked up in the table as a key, and the value (string) is what replaces it, if it exists.
- function: Called with the string that matched the pattern, should return the string to replace the matched pattern.
An optional final argument can be provided which specifies the maximum number of substitutions to make (for example, stop after 2 replacements)
Various Examples
-- Simple replacement
string.gsub("I love tacos!", "tacos", "Roblox") --> I love Roblox! 1
-- Using a pattern (hint: %w+ matches whole words)
string.gsub("I like red!", "%w+", "word") --> word word word 3
-- Replacement table
string.gsub("I play Roblox.", "%w+", {I="Je", play="joue à"}) --> Je joue à Roblox. 3
-- Replacement function
string.gsub("I have 2 cats.", "%d+", function(n) return tonumber(n) * 12 end) --> I have 24 cats. 1
-- Replace only twice
string.gsub("aaa", "a", "b", 2) --> "bba", 2
Tham Số
match
Looks for the first match of pattern in the string s. If a match is found, it is returned; otherwise, it returns nil. A third, optional numerical argument, init, specifies where to start the search; its default value is 1 and can be negative.
Lợi Nhuận
split
Splits a string into parts based on the defined separator character(s), returning a table of ordered results.
If an empty "slice" is located, that part will be returned as an empty string. For instance string.split("abc||def", "|") will return a table with three strings: "abc", "", and "def".
local values = input:split(",")print(values[1], values[2], values[3])
Also note that whitespace from the original string will be preserved, for example string.split("abc _ def", "_") will honor the whitespace on both sides of the _ separator. By default, the separator character is , but you can specify an alternative character or series of characters.
Corner Cases
Empty String
"" --> ""
Empty Slices
"foo,,bar" --> "foo", "", "bar"",foo" --> "", "foo""foo," --> "foo", """," --> "", """,," --> "", "", ""
Whitespace Preserved
" whitespace " --> " whitespace ""foo , bar" --> "foo ", " bar"
Invalid UTF-8
"\xFF" --> "\xFF""\xFD,\xFE" --> "\xFD", "\xFE"
Unicode
"," --> U+FF0C FULLWIDTH COMMA"我很高兴,你呢?" --> "我很高兴", "你呢?""•" --> U+2022 BULLET"hello•world" --> "hello", "world"
Tham Số
Lợi Nhuận
unpack
Extracts the values packed in the provided binary string based on the first argument, format, which should match the one originally used to pack() the string; see here for options. The optional third parameter determines the byte at which the reading starts.
Lợi Nhuận
The values packed into the provided binary string, plus the index of the first unread byte.