ungetc()

Places a character back into a stream.

  #include <stdio.h>
  
  int ungetc(int c, FILE *stream);    

c

The character to return to a stream.

stream

A pointer to a file stream.

The ungetc() function places character c back into stream's buffer. The next read operation will read the character placed by ungetc(). Only one character can be pushed back into a buffer until a read operation is performed.

The function's effect is ignored when an fseek(), fsetpos(), or rewind() operation is performed.

ungetc() returns c if it is successful and returns EOF if it fails.

This facility may not be available on configurations of the EWL that run on platforms without file systems.

#include <stdio.h>

#include <stdlib.h>

int main(void)

{

FILE *f;

int c;

// create a new file for output and input

if ( (f = fopen("double.txt", "w+")) == NULL) {

printf("Can't open.\n");

exit(1);

}

// output text to the file

fprintf(f, "The quick brown fox\n");

fprintf(f, "jumped over the moon.\n");

// move the file position indicator

// to the beginning of the file

rewind(f);

printf("Reading each character twice.\n");

// read a character

while ( (c = fgetc(f)) != EOF) {

putchar(c);

// Put the character back into the stream

ungetc(c, f);

c = fgetc(f);// read the same character again

putchar(c);

}

fclose(f);

return 0;

}

Output

Reading each character twice.

TThhee qquuiicckk bbrroowwnn ffooxx

jjuummppeedd oovveerr tthhee mmoooonn..