ungetc

#include <stdio.h>

int ungetc  (
    int   iChar,       /* character to store */
    FILE* stream);     /* file stream        */

The function ungetc stores a character back into the data stream. The parameter iChar defines the character to store. The parameter stream is a file pointer defining the data stream to write to.

The function is included in the library RL-FlashFS. The prototype is defined in the file stdio.h.

The function can be invoked only once between function calls that read from the data stream. Subsequent calls to ungetc fail with an EOF return value.

• iChar - on success.
• EOF - on error.

fgetc, fputc

#include <rtl.h>
#include <stdio.h>

void main (void)  {
  int c;
  FILE *fin;

  fin = fopen ("Test.txt","r");
  if (fin != NULL)  {
    while ((c = fgetc (fin)) == ' ');            // Skip leading spaces
    ungetc (c, fin);                             // Unget the first non-space
    ungetc (c, fin);                             // This call fails with EOF. The file cursor
                                                 // is now positioned to a non-space character
    fclose (fin);
  }
}