In the following working code; instead of using *tofind, if I directly use the comparison
if(*argv[i] == "and")
it fails.
Why would that be?
/**
* Find index of the word "and"
* ./a.out alice and bob
*/
int main(int argc, char **argv) {
int i = 0;
char *tofind = "and";
while (argv[i] != NULL) {
if(*argv[i] == *tofind) {
printf("%d\n", i + 1);
break;
}
++i;
}
return 0;
}
if(*argv[i] == "and") shouldn't compile, I think you mean if (argv[i] == "and"), that would compare the pointers of the two, not the string content.
if (*argv[i] == *tofind) doesn't work as you expected either, it only compares the first character.
To compare strings, use strcmp():
if (strcmp(argv[i], tofind) == 0)
A "char*" is officially a pointer to a single char, for example to find points to a letter 'a'. You know that there are two more chars and a nul char, but officially it points to a single char.
Therefore, *argv[i] is the first character of an argument, and *tofind is always the letter 'a', so your code checks if the first character of an argument is an 'a'. Look at the strcmp function, which compares whole strings.
look at the type of
*argv[i] //its type is char
and of "and"
"and" //its type is const char * as it is decayed into pointer
so thats why you are unable to compare them. while the type of
*tofind
is char and you can now compare the two.for more details see FAQs section 6.
charnot string for string compare usestrcmplook more cplusplus.com/reference/cstring/strcmp