strcmp not working?

Question

I have a strcmp function as so:

if (strcmp(userInput, "Yes") == 0)

For some reason, it will not enter the if statement, even though I am sure the userinput definitely equals Yes. Anyone have any clue whats wrong?

You probably got your user input from `fgets`, which leaves the newline attached. — Daniel Fischer, Dec 11 '12 at 18:29
How are you getting the `usrInput`, and what type is that? More info is needed — Mike, Dec 11 '12 at 18:29
`fprintf(stderr, "\"%s\", userInput);` may help you see what it really contains (alternative, print out individual bytes of the string in hexadecimal). — Jerry Coffin, Dec 11 '12 at 18:30
You can check the exact contents of `userInput` in a memory window in your debugger. — Dabbler, Dec 11 '12 at 18:32
Too little information to answer, end of story. A flood of guessing what the rest of the code might be shouldn't be necessary. Simply post the full code. — Lundin, Dec 11 '12 at 19:18

score 3 · Answer 1 · answered Dec 11 '12 at 18:33

3

Make sure you're including the proper header, i.e. <string.h>.
If you're getting userInput from e.g. fgets(), make sure there's no line termination at the end, it will interfere with a comparison written like that.

answered Dec 11 '12 at 18:33

unwind

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score 2 · Answer 2 · answered Dec 11 '12 at 18:31

2

To avoid troube with a tailing linebreak you could maybe check just the first 3 chars:

if(strncmp(userInput, "Yes", 3) == 0)

answered Dec 11 '12 at 18:31

rekire

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What if the input is "YesASDASD"? – Dec 11 '12 at 18:33
Well that would match too, but depending on the usecase it could be enough. – rekire Dec 11 '12 at 18:36
It worked for me where strcmp didn't work. I suppose it was due to one string length wasn't well defined. – Lorenzo Lerate Aug 16 '16 at 10:57

score 1 · Answer 3 · answered Dec 11 '12 at 18:36

As is, your code is fine. That is not the problem.

I suspect you're doing this:

fgets(userInput, sizeof(userInput), stdin);
if(strcmp(userInput, "Yes") == 0)

Which is giving you a newline char:

['Y']['e']['s']['\n']

You can fix that any number of ways:

if(strcmp(userInput, "Yes\n") == 0)

Is probably the easiest. Or you could get input via scaf:

scanf("%s", userInput);

score 0 · Answer 4 · answered Dec 11 '12 at 18:54

0

You can typecast if you need help.

//I am assuming usrInput is a char Array

string str(usrInput);
//string class has a constructor that takes a NULL-terminated C-string
if (str == "Yes")
{
   //do what ever you wanted to in the loop
}

answered Dec 11 '12 at 18:54

crh225

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This will not succeed in C – chux - Reinstate Monica Mar 15 '15 at 21:09

strcmp not working?

4 Answers4