La mayoría de las veces cuando lees que usan la función feof está mal. En mi experiencia se vió que es muy fácil de llamarla al tiempo incorrecto y procesar algo dos veces creyendo que EOF no fue alcanzado.
int c; while (( c = getchar()) != EOF){ }
int c; while (( c = getc(fp)) != EOF){ }
Intentá evitar usar char para el tipo c. getchar retorna el siguiente caracter casteado a un unsigned char y luego a un int. Esto significa que en la mayoría de las plataformas ‘sanas’ el valor de EOF y valores válidos char en ‘c’ no sobreescriben así que nunca accidentalmente detectarás EOF como un caracter ’normal’.
ESTAS RESPUESTAS USAN FEOF QUE PARA MI NO SON NECESARIAS.
How you detect EOF depends on what you’re using to read the stream:
function result on EOF or error
fgets() NULL fscanf() number of succesful conversions less than expected fgetc() EOF fread() number of elements read less than expected
Check the result of the input call for the appropriate condition above, then call feof() to determine if the result was due to hitting EOF or some other error.
Using fgets():
char buffer[BUFFER_SIZE]; while (fgets(buffer, sizeof buffer, stream) != NULL) { // process buffer } if (feof(stream)) { // hit end of file } else { // some other error interrupted the read }
Using fscanf():
char buffer[BUFFER_SIZE]; while (fscanf(stream, “%s”, buffer) == 1) // expect 1 successful conversion { // process buffer } if (feof(stream)) { // hit end of file } else { // some other error interrupted the read }
Using fgetc():
int c; while ((c = fgetc(stream)) != EOF) { // process c } if (feof(stream)) { // hit end of file } else { // some other error interrupted the read }
Using fread():
char buffer[BUFFER_SIZE]; while (fread(buffer, sizeof buffer, 1, stream) == 1) // expecting 1 // element of size // BUFFER_SIZE { // process buffer } if (feof(stream)) { // hit end of file } else { // some other error interrupted read }
Note that the form is the same for all of them: check the result of the read operation; if it failed, then check for EOF. You’ll see a lot of examples like:
while(!feof(stream)) { fscanf(stream, “%s”, buffer); … }
This form doesn’t work the way people think it does, because feof() won’t return true until after you’ve attempted to read past the end of the file. As a result, the loop executes one time too many, which may or may not cause you some grief.