std::feof - cppreference.com

Verifica se o fim do fluxo determinado arquivo foi atingido.

Valor diferente de zero se o fim do fluxo foi atingido, de outro modo.. 0

Original:

This function only reports the stream state as reported by the most recent I/O operation, it does not examine the associated data source. For example, if the most recent I/O was a std::fgetc, which returned the last byte of a file, std::feof returns non-zero. The next std::fgetc fails and changes the stream state to end-of-file. Only then std::feof returns zero.

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Em utilização normal, o processamento pára no fluxo de entrada de qualquer erro, e feof std::ferrror são então utilizados para distinguir entre as condições de erro diferentes.

#include <cstdio>
#include <cstdlib>

int main()
{
    FILE* fp = std::fopen("test.txt", "r");
    if(!fp) {
        std::perror("File opening failed");
        return EXIT_FAILURE;
    }

    int c; // note: int, not char, required to handle EOF
    while ((c = std::fgetc(fp)) != EOF) { // standard C I/O file reading loop
       std::putchar(c);
    }

    if (std::ferror(fp))
        std::puts("I/O error when reading");
    else if (std::feof(fp))
        std::puts("End of file reached successfully");
}