C : using getchar() in double while loop - stuck in loop?

Question

Im using this double while loop. Im new to C.

int crawler; char *desired[100]; crawler = getchar(); while(crawler != EOF) { int i = 0; while((crawler != '\n') && (crawler != EOF)) { desired[i] = crawler; i++; crawler = getchar(); } printf("%s", desired); }

I just dont see why Im getting infinite loop in here (LLLLLLLLL..). Stdin looks like this:

Lorem(newline) Ipsum(newline) Beach(newline) Crocodile(newline) Crox(newline) C(EOF)

Any idea? thanks.

char *desired[100]; -> char desired[100];. Also turn on compiler warnings (gcc -Wall ...) and pay attention to them ! — Paul R
– Paul R, Commented Oct 18, 2017 at 10:59
1.) printf("%s", desired); <- you can't guarantee desired is a string here, it probably doesn't contain a terminating \0 byte! 2.) your inner loop will happily overflow desired, add a check! — user2371524
– user2371524, Commented Oct 18, 2017 at 11:01
And don't forget that char strings in C are really called null-terminated byte strings. That null-terminator Is important to not forget. — Some programmer dude
– Some programmer dude, Commented Oct 18, 2017 at 11:01

melpomene · Accepted Answer · 2017-10-18 11:11:47Z

Your outer loop ends when crawler is EOF.

Your inner loop ends when crawler is '\n' or EOF.

Only the inner loop reads input (by calling getchar).

Therefore: As soon as the first '\n' is read, the inner loop is never re-entered (the condition rejects '\n'), but the outer loop doesn't end, and it never changes the value of crawler.

Result: The outer loop spins without reading any input.

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