ignore extra spaces when using fgets

Question

I'm using fgets with stdin to read in some data, with the max length I read in being 25. With one of the tests I'm running on this code, there are a few hundred spaces after the data that I want - which causes the program to fail.

Can someone advise me as to how to ignore all of these extra spaces when using fgets and go to the next line?

Answer 1

Use fgets() iteratively, then scan the string to see whether it is all spaces (and whether it ends with a newline) and ignore it if it is. Or use getc() or getchar() in a loop instead?

char buffer[26];

while (fgets(buffer, sizeof(buffer), stdin) != 0)
{
    ...process the first 25 characters...
    int c;
    while ((c = getchar()) != EOF && c != '\n')
        ;
}

That code simply ignores all characters up to the next newline. If you want to ensure that they are spaces, add a test in the (inner) loop - but you have to decide what to do if the character is not a space.

Answer 2

Spelling out the suggestion given by Jonathan Leffler about getc():

I assume you have a loop like this:

while (!feof(stdin)) {
  fgets(buf, 25, stdin);
  ...
}

change it like this:

while (!feof(stdin)) {
  int read = fgets(buf, 27, stdin);
  if (read > 26) { // the line was *at least* as long as the buffer
    while ('\n' != getc()); // discard everything until the newline character
  }
  ...
}

Edit: Ah, Jonathan is faster than I am at writing C. :)

Answer 3

Try this code , for removing trailing spaces.

 char str[100] ;
    int i ;
    fgets ( str , 80 , stdin ) ;
    for ( i=strlen(str) ; i>0 ; i-- )
    {
            if ( str[i] != ' ' )
            {
                    str[i+1]='\0';
                    break ;
            }
    }