[LUA 5.1] string.byte

Returns the internal numerical codes of the characters s[i], s[i+1], ···, s[j]. (Defaults: i=1, j=i)

print(string.byte("ABCD",2,2)) -- 66
print(string.byte("ABCD",2,3)) -- 66 67
print(string.byte("ABCD",1,3)) -- 65 66 67

If i or j is negative, it counts the characters from last character backwards.

print(string.byte("ABCD",-2,-2)) -- 67
print(string.byte("ABCD",-2,-1)) -- 67 68
print(string.byte("ABCD",-3,-1)) -- 66 67 68

Note: Numerical codes are not necessarily portable across platforms.

i and j are optional parameters. If except the s no parameter is given, i is set to 1 and j, too.

print(string.byte("ABCD")) -- 65
print(string.byte("")) -- nil, because of empty string

If except the s and a second parameter is given, i and j are set to the value of the second parameter.

print(string.byte("ABCD",3)) -- 67
print(string.byte("ABCD",4)) -- 68
print(string.byte("ABCD",10)) -- nil, because the string is to short

See the function string.char for converting the internal numerical code of characters back to strings.