ungetc: Put a character back to the input stream : ungetc « stdio.h « C / ANSI-C

1. C / ANSI-C
2. stdio.h
3. ungetc

ungetc: Put a character back to the input stream

    


//Declaration:  int ungetc(int ch, FILE *stream); 
//Return:       returns ch on success or EOF on failure. 

#include <stdio.h>

int main ()
{
  FILE * fp;
  int c;
  char buffer [256];
  fp = fopen ("test.txt","rt");
 
  if (fp==NULL)
    perror ("Error opening file");
  else {
    while (!feof (fp))
    {
      c=getc (fp);
      if (c == '#')
        ungetc ('@',fp);
      else
        ungetc (c,fp);
      fgets (buffer,255,fp);
      fputs (buffer,stdout);
    }
  }

  return 0; 
}

           
       

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