Lua string

Example

string1 = "Lua"
print("\\"String 1 is\\"",string1)
string2 = 'runoob.com'
print("String 2 is",string2)
string3 = [["Lua tutorial"]]
print("String 3 is",string3)

The output of the above code execution is as follows:

"String 1 is"    Lua
String 2 is    runoob.com
String 3 is    "Lua tutorial"

Escape characters are used to represent characters that cannot be displayed directly, such as back key, enter key, etc. For example, double quotation marks can be used in string conversion "\"" .

All escape characters and their corresponding meanings:

> string.gsub("aaaa","a","z",3);
zzza    3

> string.find("Hello Lua user", "Lua", 1) 
7    9

> string.reverse("Lua")
auL

> string.format("the value is:%d",4)
the value is:4

> string.char(97,98,99,100)
abcd
> string.byte("ABCD",4)
68
> string.byte("ABCD")
65
>

string.len("abc")
3

> string.rep("abcd",2)
abcdabcd

> print("www.runoob.".."com")
www.runoob.com

> for word in string.gmatch("Hello Lua user", "%a+") do print(word) end
Hello
Lua
user

> = string.match("I have 2 questions for you.", "%d+ %a+")
2 questions

> = string.format("%d, %q", string.match("I have 2 questions for you.", "(%d+) (%a+)"))
2, "questions"

string.sub(s, i [, j])

Example

-- character string
local sourcestr = "prefix--runoobgoogletaobao--suffix"
print("\\n Original string", string.format("%q", sourcestr))
-- Intercepted parts, 4th to 15th
local first_sub = string.sub(sourcestr, 4, 15)
print("\\n First interception", string.format("%q", first_sub))
-- Prefix string, 1st to 8th
local second_sub = string.sub(sourcestr, 1, 8)
print("\\n Second interception", string.format("%q", second_sub))
-- Capture the last 10
local third_sub = string.sub(sourcestr, -10)
print("\\n Third interception", string.format("%q", third_sub))
-- Index out of bounds, output original string
local fourth_sub = string.sub(sourcestr, -100)
print("\\n Fourth interception", string.format("%q", fourth_sub))

The result of the above code execution is:

Original String    "prefix--runoobgoogletaobao--suffix"

First interception    "fix--runoobg"

Second interception    "prefix--"

Third interception   "ao--suffix"

Fourth interception    "prefix--runoobgoogletaobao--suffix"

Example

string1 = "Lua";
print(string.upper(string1))
print(string.lower(string1))

The result of the above code execution is:

LUA
lua

Example

string = "Lua Tutorial"
-- Find String
print(string.find(string,"Tutorial"))
reversedString = string.reverse(string)
print("The new string is",reversedString)

The result of the above code execution is:

5    12
The new string is    lairotuT auL

Example

string1 = "Lua"
string2 = "Tutorial"
number1 = 10
number2 = 20
-- Basic string formatting
print(string.format("Basic formatting %s %s",string1,string2))
-- Date formatting
date = 2; month = 1; year = 2014
print(string.format("Date formatting %02d/%02d/%03d", date, month, year))
-- Decimal formatting
print(string.format("%.4f",1/3))

The result of the above code execution is:

Basic formatting Lua Tutorial
Date formatting 02/01/2014
0.3333

Other examples:

Example

string.format("%c", 83)                 -- outputS
string.format("%+d", 17.0)              -- output+17
string.format("%05d", 17)               -- output00017
string.format("%o", 17)                 -- output21
string.format("%u", 3.14)               -- output3
string.format("%x", 13)                 -- outputd
string.format("%X", 13)                 -- outputD
string.format("%e", 1000)               -- output1.000000e+03
string.format("%E", 1000)               -- output1.000000E+03
string.format("%6.3f", 13)              -- output13.000
string.format("%q", "One\\nTwo")         -- output"One\\
                                        -- 　　Two"
string.format("%s", "monkey")           -- output  monkey
string.format("%10s", "monkey")         -- output  monkey
string.format("%5.3s", "monkey")        -- output  mon

Example

-- character conversion
-- Convert first character
print(string.byte("Lua"))
-- Convert the third character
print(string.byte("Lua",3))
-- Convert the first character at the end
print(string.byte("Lua",-1))
-- Second character
print(string.byte("Lua",2))
-- Convert the second character at the end
print(string.byte("Lua",-2))
-- Convert integer ASCII code to characters
print(string.char(97))

The result of the above code execution is:

76
97
97
117
117
a

Example

string1 = "www."
string2 = "runoob"
string3 = ".com"
-- Using Make string connections
print("connection string",string1..string2..string3)
-- String Length
print("String Length ",string.len(string2))
-- Copy string twice
repeatedString = string.rep(string2,2)
print(repeatedString)

The result of the above code execution is:

connection string   www.runoob.com
String Length    6
runoobrunoob

Example

s = "Deadline is 30/05/1999, firm"
date = "%d%d/%d%d/%d%d%d%d"
print(string.sub(s, string.find(s, date)))    --> 30/05/1999

The following table lists all the character classes supported by Lua:

Single character (except ^$()%.[]*+-? outside): paired with the character itself

• . (dot): Pairing with any character

• %a : Pair with any letter

• %c : Pair with any controller (for example,n)

• %d : Pair with any number

• %l : Pair with any lowercase letter

• %p : Pair with any punctuation punctuation

• %s Pairing with white space characters

• %u : Pair with any uppercase letter

• %w : Paired with any letter / number

• %x Paired with any hexadecimal number

• %z : Pair with any character that represents 0

• %x (here x is a non-alphanumeric character): paired with the character x. It is mainly used to deal with functional characters in expressions ^$()%.[]*+-? ), such as %% and % pairing

• [数个字符类] With any [] The character class pairs contained in the. For example [%w_] With any letter / number 或下划线符号(_) Pairing

• [^Several character classes]: Unlike any that is not included in the []``character class pairing in. For example  ``[^%s] pair with any non-white space character

When the above character class is written in uppercase, it is paired with any character other than this character class. For example, %S %S indicates pairing with any non whitespace characterfor example, '%A' non-alphabetic characters:

> print(string.gsub("hello, up-down!", "%A", "."))
hello..up.down.    4

The number 4 is not part of the result of the string, it is gsub , the second result returned represents the number of replacements that have occurred.

There are some special characters in pattern matching that have special meanings. The special characters in Lua are as follows:

( ) . % + - * ? [ ^ $

'%' used as an escape character for special characters, so '%.' matching point '%%' matching character '%' . Escape character '%' it can be used not only to escape special characters, but also to all non-alphabetic characters.

Pattern entries can be:

• A single character class matches any single character in that category

• A single character class is compared to a '*' that will match zero or more characters of this class This entry always matches the string as long as possible;

• A single character class is compared to a '+' that will match one or more characters of this class This entry always matches the string as long as possible;

• A single character class is compared to a '-' that will match zero or more characters of this class, unlike '*', this entry always matchesthe shortest possible string;

• A single character class is compared to a '?' that will match zero or acharacter of this class Whenever possible, it will match one;

• %n , where n can range from 1 to 9; this entry matches a substring equal to the n catch (described later).

• %bxy , where x and y are two explicit characters; this entry matches a string that starts with x and ends with y, where x and y are balanced It means that if you read the string from left to right, it will be + 1 every time you read an x,-1 when you read a y, and the y at the end is the first yto count to 0. For example, an entry %b() expressions that can match to parenthesis balance.

• %f[set] , which refers to the border pattern; this entry matches to a set an empty string before a character within, and the previous character in this position does not belong to set . Set set the meaning is as described earlier. The start and end points of the matched empty string are calculated as if there is a character ‘\0’ there.

Mode:

A pattern refers to a sequence of pattern entries. Add a symbol to the frontof the pattern '^' matches the anchor from the beginning of the string. Add a symbol to the end of the pattern '$' anchors the matchingprocess to the end of the string. If '^' and '$' when they appearin other places, they have no special meaning, they only represent themselves.

Capture:

Patterns can enclose a subpattern internally in parentheses; these sub patterns are called catches. When the match is successful, the substringsin the string matched by the catch are saved for future use. The catches are numbered in the order of their left parenthesis. For example, for a pattern``”(a*(.)%w(%s*))”`` that matches to the "a*(.)%w(%s*)" issaved in the first catch (and therefore number 1); by "." the matching character is catch 2, and the part that matches to “% s*” is number 3.

As a special case, empty capture () will be captured to the position ofthe current string (which is a number). For example, if you set the pattern "()aa()" act on a string "flaaap" two catches will be produced: 3 and 5.