沉默标准/标准标准

Question

什么是与this C++ answer的C等价的临时 silencing output to cout/cerr，然后恢复 it？

如何保持沉默和恢复stderr/stdout

(需要这样做才能使我调用的第三方库中的噪音保持安静，并在调用后恢复。)

Answer 1

这是一次可怕的黑客攻击，但应该有效：

#include <stdio.h>
#include <unistd.h>


int
suppress_stdout(void)
{
    fflush(stdout);
    int fd = dup(STDOUT_FILENO);
    freopen("/dev/null", "w", stdout);
    return fd;
}

void
restore_stdout(int fd)
{
    fflush(stdout);
    dup2(fd, fileno(stdout));
    close(fd);
}

int
main(void)
{
    puts("visible");
    int fd = suppress_stdout();
    puts("this is hidden");
    restore_stdout(fd);
    puts("visible");
}

Answer 2

#include <stdio.h>

#ifdef _WIN32
#define NULL_DEVICE "NUL:"
#define TTY_DEVICE "COM1:"
#else
#define NULL_DEVICE "/dev/null"
#define TTY_DEVICE "/dev/tty"
#endif

int main() {
    printf("hello!\n");

    freopen(NULL_DEVICE, "w", stdout);
    freopen(NULL_DEVICE, "w", stderr);

    printf("you CAN'T see this stdout\n");
    fprintf(stderr, "you CAN'T see this stderr\n");

    freopen(TTY_DEVICE, "w", stdout);
    freopen(TTY_DEVICE, "w", stderr);

    printf("you CAN see this stdout\n");
    fprintf(stderr, "you CAN see this stderr\n");
    return 0;
}