String

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Properties

Introduction

Strings are sequences of characters, letters, numbers, letters AND numbers, symbols, and so forth.

A script of

x = "Hi mom" y = "123456" z = "Bob12345" n = "abc!@#$%^&*()123456789"

print(x) print(y) print(z) print(n)

will print in the output bar Hi mom, 123456, Bob12345, and abc!@#$%^&*()123456789. Strings differ from Numbers in that you can't allocate a name like "Bob" to numbers.

Another important note with strings is that if you try to perform arithmetic on a string value, it will try to convert the string to a number. If your value can't be converted to a number, you will get an error.

print("5" + 1)
print ("whoops"+1)

6

Cmd:1: attempt to perform arithmetic on a string value

In the first example, "5" was converted from a string to a number (notice "5" was in quotes, but 1 was not.) In the second example "whoops" could not be converted to a number, because it was a word.

print("50" == 50) -- false, because a string is not equal to a number. print(tostring(50) == "50") -- true, because you converted the number 50 to a string print(tonumber("50") == 50) -- true, because you converted the string "50" to a number print(50 .. "" == "50") -- true, because you tacked on an empty string to the end of the number 50, converting 50 to a string.

Converting a string to a number

You can easily convert a string to a number by using the tonumber() function. This function takes one argument, which is a string, and will return the string into a number. The string must be a sequence of characters that resembles a number, such as "5128", "2", etc. Any strings that don't resemble numbers, such as "Hello", will return nil.

This is an example of tonumber() usage. a = "123" b = 5 + tonumber(a) --tonumber() usage here

print(b) --128

Advanced

This will also work with hexadecimal numbers: print(0xf == 15) -- true, because 0xf is a hexadecimal number which equals 15 print(tonumber("0xf") == 15) -- true, because you converted the string "0xf" to a number, 0xf

as well as with other based numbers, but you have to specify the base:

print(tonumber("00001111",2)) -- prints 15 print(tonumber("00001111",2)==15) -- prints true

print(tonumber("774",8)) -- prints 508 print(tonumber("774",8)==508) -- prints true

Literals

print("hello") print('hello') print(hello)

Will all result in: hello [1]

This allows you to nest a string within another string:

print('hello "Lua user"')
print("Its [[content]] hasn't got a substring.")
print([[Let's have more "strings" please.]])

hello "Lua user" Its content hasn't got a substring.

Let's have more "strings" please.

Multiline Literals

print([[Multiple lines of text
can be enclosed in double square
brackets.]])

Multiple lines of text

can be enclosed in double square

brackets.

You can also use normal quotation marks with a backslash at the end of each line to create multiline strings:

local str = "line1\
line2\
line3"
print(str)

line1 line2

line3

Nesting square brackets

Nested brackets rely on the use of equals signs to distinguish one nested bracket from another.

Example:

print([==[
one [=[two]=] one
]=])
print([===[
one [=[two]=] one
]===])

one [=[two]=] one

one [=[two]=] one

Escaping

In single or double quotes, but not block quotes, you can use backslashes (\) to embed any character.

Backslash followed by certain letters have special meanings (see the Lua Manual).

A backslash followed by punctuation or newline overrides any special meaning and puts the character in the string. This is most useful in put quotes or backslash into a quoted string. print( 'String \'abc\ ) print( "String with \" \\ and \' " ) A backslash followed by 1-3 numbers represents the string.byte value of that number.

print( "\104\105" )

hi

Be careful if you use fewer than 3 numbers ("\0" for example) and a number comes after it. print( "\000123" ~= "\0123" )

See Also

Programming in Lua 2.4 -- Strings

Lua 5.1 Reference Manual

StringsTutorial

StringValue