Lua Programming/stringlib
Facilities[edit | edit source]
string.byte[edit | edit source]
string.char[edit | edit source]
string.dump[edit | edit source]
string.find[edit | edit source]
string.format[edit | edit source]
string.gmatch[edit | edit source]
string.gsub[edit | edit source]
string.len[edit | edit source]
Usage[edit | edit source]
string.len(STRING)
Description[edit | edit source]
The string.len function returns the length of the string argument.
print (string.len("Llanfairpwllgwyngyllgogerychwyrndrobwllllantysiliogogogoch")) -- Returns 58
Embedded nul characters[edit | edit source]
Embedded nul characters do not terminate the string and are also counted by this function.
print (string.len("ab\000cd\000")) -- Returns 6
The length operator can also be used to determine the length of a string[edit | edit source]
The lua programming language provides a length operator, which can also be used to determine the length of a string:
print (#"Llanfairpwllgwyngyllgogerychwyrndrobwllllantysiliogogogoch") -- Returns 58
string.lower[edit | edit source]
string.match[edit | edit source]
string.rep[edit | edit source]
string.reverse[edit | edit source]
Usage[edit | edit source]
string.reverse(STRING)
Description[edit | edit source]
The string.reverse function can be used for reversing string and returns the string with its character order reversed:
print (string.reverse("anut fo raj a rof tun A")) -- A nut for a jar of tuna
string.sub[edit | edit source]
Usage[edit | edit source]
string.sub(STRING, STARTPOS [, ENDPOS])
Description[edit | edit source]
The string.sub function returns a substring of the string argument from a start position, and an optional end position.
print (string.sub("cheese salad sandwich",8)) -- position 8 onwards gives us "salad sandwich" print (string.sub("cheese salad sandwich",1,12) -- positions 1 to 12 gives us "cheese salad"
The start position cannot be omitted, but the end position may be omitted[edit | edit source]
Note that the start position is not optional, so for substrings starting at the first position, a parameter of one must be provided:
-- This does not work print (string.sub("cheese salad sandwich",,12) -- we cannot omit the start position -- To fix this, we must provide a substring position print (string.sub("cheese salad sandwich",1,12) -- we want a substring from position 1
The end position can be omitted or negative[edit | edit source]
Without an end position, the substring continues to the end of the string:
print (string.sub("cheese salad sandwich",8)) -- position 8 onwards gives us "salad sandwich"
String positions may be negative[edit | edit source]
The end position can be negative. A negative value indicates the number of characters from the end, with -1 meaning the last character, -2 meaning the last but one character, etc:
print (string.sub("cheese salad sandwich",-8)) -- start 8 characters from the end gives "sandwich" print (string.sub("cheese salad sandwich",1,-9)) -- drop " sandwich" to give "cheese salad"