cin.get gets one extra character?

Question

Possible Duplicate:
Why is iostream::eof inside a loop condition considered wrong?

I was reading a group of characters via cin.get() and I noticed that my cin.get() was getting an exra character at the end of the input. Might anyone know how to fix this? Here's my code:

unsigned char c;

while(!cin.eof())
{
   c = cin.get();
   cout << (int)c << endl;
}

My issue is that the character it gets is one of 255 ascii value. I simply don't want it to get this extra character, but if the user enters in a ascii value of 255 without it being a garbage character at the end, then that should be fine. An example would be so for my output:

if I entered in abc\n in my output:

I get 97 98 99 10 255

but I want: 97 98 99 10

Any ideas on how to fix this? Thanks!

Why `!cin.eof()`? Is the input from a file.? – Coding Mash Dec 03 '12 at 18:49 — Coding Mash, Dec 03 '12 at 18:49

score 3 · Accepted Answer · edited May 23 '17 at 10:34

3

Never use cin.eof() as a loop condition. It almost always produces buggy code, as it has here.

Instead, try:

int c;
while ( (c=cin.get()) != EOF ) {
  cout << c << endl;
}

Or:

char c;
while (cin.get(c)) {
  cout << (int)c << endl;
}

edited May 23 '17 at 10:34

Community

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answered Dec 03 '12 at 18:54

Robᵩ

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Although you should probably not use `EOF` since the trait may return another value on end of file than `-1`, right? – Alexis Wilke Jun 09 '19 at 05:37
1

@AlexisWilke - Perhaps generally, but not specifically for `cin`. `std::cin` will always use `std::char_traits`, which uses `EOF`. – Robᵩ Jun 18 '19 at 03:58

score 3 · Answer 2 · answered Dec 03 '12 at 18:55

The get() function with no arguments returns an int_type, not a char. At the end of the stream, it returns a special non-character value that indicates end of file (usually -1). By assigning the result of cin.get() directly to an unsigned char, you are inadvertently throwing away this eof information. The relevant documentation quote is:

1) reads one character and returns it if available. Otherwise, returns Traits::eof() and sets failbit and eofbit.

cin.get gets one extra character?

2 Answers2