string
The string namespace contains functions related to strings.
string.format
The string.format function produces a string by formatting a number of other values according to a specification string.
It’s similar to the printf function in C, and other similar functions in other programming languages.
string.format(spec, values...)Examples
> string.format("Hello, %s!", "Ander")
"Hello, Ander!"
> string.format("There are %d lights", 4)
"There are 4 lights"The string.format function is most useful when you use more complex format specifications.
Specification Syntax
The specification is a string that includes formatting verbs that are introduced with the % character.
The function call must then have one additional argument for each verb sequence in the specification.
The verbs are matched with consecutive arguments and formatted as directed, as long as each given argument is convertible to the type required by the format verb.
By default, % sequences consume successive arguments starting with the first.
Introducing a [n] sequence immediately before the verb letter, where n is a decimal integer, explicitly chooses a particular value argument by its one-based index.
Subsequent calls without an explicit index will then proceed with n+1, n+2, etc.
The function produces an error if the format string requests an impossible conversion or accesses more arguments than are given. An error is also produced for an unsupported format verb.
Verbs
The specification may contain the following verbs.
| Verb | Result |
|---|---|
%% | Literal percent sign, consuming no value. |
%t | Convert to boolean and produce true or false. |
%b | Convert to integer number and produce binary representation. |
%d | Convert to integer and produce decimal representation. |
%o | Convert to integer and produce octal representation. |
%x | Convert to integer and produce hexadecimal representation with lowercase letters. |
%X | Like %x, but use uppercase letters. |
%e | Convert to number and produce scientific notation, like -1.234456e+78. |
%E | Like %e, but use an uppercase E to introduce the exponent. |
%f | Convert to number and produce decimal fraction notation with no exponent, like 123.456. |
%g | Like %e for large exponents or like %f otherwise. |
%G | Like %E for large exponents or like %f otherwise. |
%s | Convert to string and insert the string’s characters. |
%q | Convert to string and produce a JSON quoted string representation. |
string.join
string.join all items in an array into a string, using a character as separator.
string.join(list, separator)Examples
> string.join(["foo", "bar", "baz"], "-")
"foo-bar-baz"
> string.join(["foo", "bar", "baz"], ", ")
"foo, bar, baz"
> string.join(["foo"], ", ")
"foo"string.replace
string.replace searches a string for a substring, and replaces each occurrence of the substring with a replacement string.
string.replace(string, substring, replacement)Examples
> string.replace("1 + 2 + 3", "+", "-")
"1 - 2 - 3"string.split
string.split produces a list by dividing a string at all occurrences of a separator.
split(list, separator)Examples
> string.split("foo,bar,baz", "," )
["foo", "bar", "baz"]
> string.split("foo", ",")
["foo"]
> string.split("", ",")
[""]string.to_lower
string.to_lower converts all uppercase letters in a string to lowercase.
Examples
> string.to_lower("HELLO")
"hello"string.to_upper
string.to_upper converts all lowercase letters in a string to uppercase.
Examples
> string.to_upper("hello")
"HELLO"string.trim
string.trim removes the specified set of characters from the start and end of a string.
string.trim(string, str_character_set)Examples
> string.trim("?!hello?!", "!?")
"hello"
> string.trim("foobar", "far")
"oob"
> string.trim(" hello! world.! ", "! ")
"hello! world."string.trim_prefix
string.trim_prefix removes the prefix from the start of a string.
If the string doesn’t start with the prefix, the string is returned unchanged.
Examples
> string.trim_prefix("helloworld", "hello")
"world"string.trim_suffix
string.trim_suffix removes the suffix from the end of a string.
Examples
> string.trim_suffix("helloworld", "world")
"hello"string.trim_space
string.trim_space removes any whitespace characters from the start and end of a string.
Examples
> string.trim_space(" hello\n\n")
"hello"Was this page helpful?
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