The GNU C Library - Character Input

Character Input

This section describes functions for performing character- and line-oriented input. These functions are declared in the header file `stdio.h'.

Function int fgetc (FILE *stream)

This function reads the next character as an unsigned char from the stream stream and returns its value, converted to an int . If an end-of-file condition or read error occurs, EOF is returned instead.

Function int getc (FILE *stream)

This is just like fgetc , except that it is permissible (and typical) for it to be implemented as a macro that evaluates the stream argument more than once. getc is often highly optimized, so it is usually the best function to use to read a single character.

Function int getchar (void)

The getchar function is equivalent to getc with stdin as the value of the stream argument.

Here is an example of a function that does input using fgetc . It would work just as well using getc instead, or using getchar () instead of fgetc (stdin) .

	int
	y_or_n_p (const char *question)
	{
	  fputs (question, stdout);
	  while (1)
	    {
	      int c, answer;
	      /* Write a space to separate answer from question. */
	      fputc (' ', stdout);
	      /* Read the first character of the line.
	         This should be the answer character, but might not be. */
	      c = tolower (fgetc (stdin));
	      answer = c;
	      /* Discard rest of input line. */
	      while (c != '\n')
	        c = fgetc (stdin);
	      /* Obey the answer if it was valid. */
	      if (answer == 'y')
	        return 1;
	      if (answer == 'n')
	        return 0;
	      /* Answer was invalid: ask for valid answer. */
	      fputs ("Please answer y or n:", stdout);
	    }
	}

Function int getw (FILE *stream)

This function reads a word (that is, an int ) from stream. It's provided for compatibility with SVID. We recommend you use fread instead (see Block Input/Output).