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