Updated at September 7, 2026 01:25 PM

Module string

Overview

The string module has everything in the standard Lua string library, and some Tarantool extensions.

In this section we only discuss the additional functions that the Tarantool developers have added.

Index

Below is a list of all additional string functions.

Name	Use
string.ljust()	Left-justify a string
string.rjust()	Right-justify a string
string.hex()	Given a string, return hexadecimal values
string.fromhex()	Given hexadecimal values, return a string
string.startswith()	Check if a string starts with a given substring
string.endswith()	Check if a string ends with a given substring
string.lstrip()	Remove characters from the left of a string
string.rstrip()	Remove characters from the right of a string
string.split()	Split a string into a table of strings
string.strip()	Remove spaces on the left and right of a string

Name

Use

string.ljust()

Left-justify a string

string.rjust()

Right-justify a string

string.hex()

Given a string, return hexadecimal values

string.fromhex()

Given hexadecimal values, return a string

string.startswith()

Check if a string starts with a given substring

string.endswith()

Check if a string ends with a given substring

string.lstrip()

Remove characters from the left of a string

string.rstrip()

Remove characters from the right of a string

string.split()

Split a string into a table of strings

string.strip()

Remove spaces on the left and right of a string

string.ljust(input-string, width[, pad-character])

Return the string left-justified in a string of length width.

Parameters:

input-string (string) — the string to left-justify
width (integer) — the width of the string after left-justifying
pad-character (string) — a single character, default = 1 space

Returns

left-justified string (unchanged if width <= string length)

Return type

string

Example:


tarantool> string = require('string')---...tarantool> string.ljust(' A', 5)---- ' A   '...

string.rjust(input-string, width[, pad-character])

Return the string right-justified in a string of length width.

Parameters:

input-string (string) — the string to right-justify
width (integer) — the width of the string after right-justifying
pad-character (string) — a single character, default = 1 space

Returns

right-justified string (unchanged if width <= string length)

Return type

string

Example:


tarantool> string = require('string')---...tarantool> string.rjust('', 5, 'X')---- 'XXXXX'...

string.hex(input-string)

Return the hexadecimal value of the input string.

Parameters:

input-string (string) — the string to process

Returns

hexadecimal, 2 hex-digit characters for each input character

Return type

string

Example:


tarantool> string = require('string')---...tarantool> string.hex('ABC ')---- '41424320'...

string.fromhex(hexadecimal-input-string)

Given a string containing pairs of hexadecimal digits, return a string with one byte for each pair. This is the reverse of string.hex(). The hexadecimal-input-string must contain an even number of hexadecimal digits.

Parameters:

hexadecimal-input-string (string) — string with pairs of hexadecimal digits

Returns

string with one byte for each pair of hexadecimal digits

Return type

string

Example:


tarantool> string = require('string')---...tarantool> string.fromhex('41424320')---- 'ABC '...

string.startswith(input-string, start-string[, start-pos[, end-pos]])

Return True if input-string starts with start-string, otherwise return False.

Parameters:

input-string (string) — the string where start-string should be looked for
start-string (string) — the string to look for
start-pos (integer) — position: where to start looking within input-string
end-pos (integer) — position: where to end looking within input-string

Returns

true or false

Return type

boolean

start-pos and end-pos may be negative, meaning the position should be calculated from the end of the string.

Example:


tarantool> string = require('string')---...tarantool> string.startswith(' A', 'A', 2, 5)---- true...

string.endswith(input-string, end-string[, start-pos[, end-pos]])

Return True if input-string ends with end-string, otherwise return False.

Parameters:

input-string (string) — the string where end-string should be looked for
end-string (string) — the string to look for
start-pos (integer) — position: where to start looking within input-string
end-pos (integer) — position: where to end looking within input-string

Returns

true or false

Return type

boolean

start-pos and end-pos may be negative, meaning the position should be calculated from the end of the string.

Example:


tarantool> string = require('string')---...tarantool> string.endswith('Baa', 'aa')---- true...

string.lstrip(input-string[, list-of-characters])

Return the value of the input string, after removing characters on the left. The optional list-of-characters parameter is a set not a sequence, so string.lstrip(...,'ABC') does not mean strip 'ABC', it means strip 'A' or 'B' or 'C'.

Parameters:

input-string (string) — the string to process
list-of-characters (string) — what characters can be stripped. Default = space.

Returns

result after stripping characters from input string

Return type

string

Example:


tarantool> string = require('string')---...tarantool> string.lstrip(' ABC ')---- 'ABC '...

string.rstrip(input-string[, list-of-characters])

Return the value of the input string, after removing characters on the right. The optional list-of-characters parameter is a set not a sequence, so string.rstrip(...,'ABC') does not mean strip 'ABC', it means strip 'A' or 'B' or 'C'.

Parameters:

input-string (string) — the string to process
list-of-characters (string) — what characters can be stripped. Default = space.

Returns

result after stripping characters from input string

Return type

string

Example:


tarantool> string = require('string')---...tarantool> string.rstrip(' ABC ')---- ' ABC'...

string.split(input-string[, split-string[, max]])

Split input-string into one or more output strings in a table. The places to split are the places where split-string occurs.

Parameters:

input-string (string) — the string to split
split-string (string) — the string to find within input-string. Default = space
max (integer) — maximum number of delimiters to process counting from the beginning of the input string. Result will contain max + 1 parts maximum

Returns

table of strings that were split from input-string

Return type

table

Example:


tarantool> string = require('string')---...tarantool> string.split("A:B:C:D:F", ":", 2)---- - A  - B  - C:D:F...

string.strip(input-string[, list-of-characters])

Return the value of the input string, after removing characters on the left and the right. The optional list-of-characters parameter is a set not a sequence, so string.strip(...,'ABC') does not mean strip 'ABC', it means strip 'A' or 'B' or 'C'.

Parameters:

input-string (string) — the string to process
list-of-characters (string) — what characters can be stripped. Default = space.

Returns

result after stripping characters from input string

Return type

string

Example:


tarantool> string = require('string')---...tarantool> string.strip(' ABC ')---- ABC...

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