How do I lowercase a string in C?
CStringLowercaseC Problem Overview
How can I convert a mixed case string to a lowercase string in C?
C Solutions
Solution 1 - C
It's in the standard library, and that's the most straight forward way I can see to implement such a function. So yes, just loop through the string and convert each character to lowercase.
Something trivial like this:
#include <ctype.h>
for(int i = 0; str[i]; i++){
str[i] = tolower(str[i]);
}
or if you prefer one liners, then you can use this one by J.F. Sebastian:
for ( ; *p; ++p) *p = tolower(*p);
Solution 2 - C
to convert to lower case is equivalent to rise bit 0x60 if you restrict yourself to ASCII:
for(char *p = pstr; *p; ++p)
*p = *p > 0x40 && *p < 0x5b ? *p | 0x60 : *p;
Solution 3 - C
Looping the pointer to gain better performance:
#include <ctype.h>
char* toLower(char* s) {
for(char *p=s; *p; p++) *p=tolower(*p);
return s;
}
char* toUpper(char* s) {
for(char *p=s; *p; p++) *p=toupper(*p);
return s;
}
Solution 4 - C
If you need Unicode support in the lower case function see this question: Light C Unicode Library
Solution 5 - C
If we're going to be as sloppy as to use tolower(), do this:
char blah[] = "blah blah Blah BLAH blAH\0";
int i = 0;
while( blah[i] |=' ', blah[++i] ) {}
But, well, it kinda explodes if you feed it some symbols/numerals, and in general it's evil. Good interview question, though.
Solution 6 - C
Are you just dealing with ASCII strings, and have no locale issues? Then yes, that would be a good way to do it.