Lua string processing

Match pattern (pattern)

• . Any single character
• %a any letter
• %c any control character
• %d any number
• %g any printable character except for whitespace
• %l All lowercase Letters
• %p All punctuation
• %s all whitespace characters
• %u all uppercase letters
• %w All letters and numbers
• %x all 16 binary digit symbols
• %x (where x is any non-alphabetic/numeric character) represents the character X. such as percent%,%. Represents a point number.%/ Represents a slash/.
• [set]Represents a union of all the characters in a set, and any one of these characters represents a match. You can use-connect, such as [0-9] to represent 0 to 9 of these 10 numbers.
• [^set]Represents the set's complement.

Character classes and special meaning symbols:

• A single character class followed by a ' * ' will match 0 or more of that type of character, matching the longest string possible.
• A single character class with a '-' will match 0 or more of that type of character, matching the shortest possible string.
• A single character class followed by a ' + ' will match one or more of the characters of that class, matching the string as long as possible.
• A single character class with a '? ' will match 0 or one of those characters.
• %n, where n can be from 1 to 9, matches the captured nth substring.
• %bxy, where x and Y are two explicit characters, the match begins with X and ends with Y. such as%b () matches a string that includes parentheses.
• %f[set], Frontier mode. Matches an empty string that precedes a character in the set, and the first character of the position does not belong to set.

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

• Returns the numeric encoding of the character S[i], s[i+1], ..., s[j]
• I default = 1,j default equals i

Cases:

str = "abcdef"print(str:byte()) --> 97，'a' 的编码值print(str:byte(2)) --> 98，'b' 的编码值print(str:byte(2, 4)) -> 98 99  100

string.char(...)

• Receives an integer as the encoded value of the character as a parameter, returning the corresponding character

Cases:

print(string.char(97, 98, 99) --> abc

string.dump(function [, strip])

• Represents a function in string form and returns. The returned string can be loaded loadstring.
• Strip is true, indicating that debug information (local variable name, line number, etc.) is removed from the function

Cases:

local function print_hello()    print("hello world")endlocal f = string.dump(print_hello, true)print(f)local a = loadstring(f)print(type(a)) --> 'function'a() --> 'hello world'

string.find(s, pattern [, init[, plain]])

• Finds the first match to pattern in the string s, returning the starting and ending positions of the match. No return nil found
• INIT specifies where to start the lookup, which defaults to 1. A negative value indicates the start of the countdown until the end of the string.
• Plain is true, the pattern match is turned off.

Cases:

str = "hello, world"print(string.find(str, "llo")) --> 3    5print(string.find(str, "world", -5)) --> 8  12print(string.find(str, "world", -4)) --> nil

string.format(formating, ...)

• sprintf with C, not supported *, H, L, L, N, p
• Add%q to format a string as two double quotes.

Cases:

str = 'a string with "quotes" and\nnew line'print(string.format("%q", str))

string.gmatch(s, pattern)

• Returns an iterator function that, each time it is called, matches s in pattern mode and returns the captured value.

Cases:

s = "hello world from Lua"g = string.gmatch(s, "%a+")print(type(g)) --> 'function', g 是一个函数print(g()) --> 'hello'，调用一次则进行一次匹配print(g()) --> 'world'，返回第二次匹配的值

s = "from=world, to=Lua"for k, v in string.gmatch(s, "(%w+)=(%w+)") do    print(k, v) --> 打印捕获到的值end

string.gsub(s, pattern, repl[, n])

• Replaces all matching pattern in a string with REPL and returns the replaced string. The second return value returns the number of matches.
• No set capture in pattern captures the entire pattern by default
• Match all By default

Cases:

s = "hello world, hello world, hello world"print(s:gsub("world", "sam")) --> hello sam, hello sam, hello sam   3

• If there are n parameters, only the first n matches are replaced.

Cases:

s = "hello world, hello world, hello world"print(s:gsub("world", "sam", 1)) --> hello sam, hello world, hello world    1print(s:gsub("world", "sam", 2)) --> hello sam, hello sam, hello world  2

• If Repl is a string, the string is replaced directly. %d in REPL indicates the number of substrings captured by the first. %0 Represents the entire match. A percent percent represents a single percentile.

Cases:

s = "hello world, hello world, hello world"print(s:gsub("(%w+)", "%1 %1", 1)) --> hello hello world, hello world, hello world  1print(s:gsub("(%w+)%s*(%w+)", "%2 %1", 1)) --> world hello, hello world, hello world    1

• If REPL is a table, the first captured value is used as the key value for each match to find the table.

Cases:

x = {}x.hello = "HELLO"x.world = "WORLD"s = "hello world, hello world, hello world"print(s:gsub("(%w+)", x)) --> HELLO WORLD, HELLO WORLD, HELLO WORLD 6

• If Repl is a function, the function is called each time the match is taken, and the capture value is passed in as a parameter to the function.

Cases:

function x(str)    return "sam"ends = "hello world, hello world, hello world"print(s:gsub("(%w+)", x)) --> sam sam, sam sam, sam sam 6

• The result of a table or function is not manipulated if it is false or nil, and is replaced if it is a string or a number.

Cases:

x = {}x.hello = "HELLO"s = "hello world, hello world, hello world"print(s:gsub("(%w+)", x)) --> HELLO world, HELLO world, HELLO world 6

function x(str)    return nilends = "hello world, hello world, hello world"print(s:gsub("(%w+)", x)) --> hello world, hello world, hello world 6

string.len(s)

• return string length

Cases:

print(string.len("hello, world")) --> 12

string.lower(s)

• Uppercase characters in s are converted to lowercase

Cases:

print(string.lower("HEllo, woRLD")) --> hello, world

string.upper(s)

• Lowercase characters in s are turned into uppercase

Cases:

print(string.upper("HEllo, woRLD")) --> HELLO, WORLD

string.match(s, pattern[, init])

• Finds the first matching pattern part in a string and returns the captured value. No return nil found.
• INIT specifies the starting position of the search. The default is 1, which can be negative.

Cases:

s = "hello world, hello world, hello world"print(string.match(s, "hello")) --> helloprint(string.match(s, "wor%a+")) --> world

string.rep(s, n[, sep])

• Connect n s with Sep and return
• Default Sep is empty, that is, there is no??? Separator

Cases:

print(string.rep("hello", 2)) --> hellohelloprint(string.rep("hello", 2, ", ")) --> hello, hello

string.reverse(s)

• Invert string s

Cases:

print(string.reverse("hello")) --> olleh

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

• Returns the substring of S, starting with I, J ends.
• I and J can be negative.
• J Default is-1, which is the end of the string.

Cases:

print(string.sub("hello", 2)) --> elloprint(string.sub("hello", 2, 4)) --> ell

string.pack(fmt, v1, v2, ...) string.packsize(fmt) string.unpack(fmt, s[, pos])

Lua string processing