Round 1
From some examples, I know how to redirect stdio to null.
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
int main()
{
int fd = open("/dev/null", O_RDWR);
int in, out, err;
if (fd < 0) {
perror("open file error!");
return -1;
}
printf("test1\n");
dup2(fd, STDIN_FILENO);
dup2(fd, STDOUT_FILENO);
dup2(fd, STDERR_FILENO);
printf("test2\n");
close(fd);
return 0;
}
After I execute the code, my console shows:
test1
test2 is redirected to /dev/null.
However, now, I would like to rollback stdio from /dev/null to standard input and output.
How do I do it?
Round 2
Thank for your reply.
Actually, I suffer a problem that a program redirects stdio (such as example 1) and forks my program (such as example 2).
example 1#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
int main()
{
int fd = open("/dev/null", O_RDWR);
if (fd < 0) {
perror("open file error!");
return -1;
}
printf("test1\n");
dup2(fd, STDIN_FILENO);
dup2(fd, STDOUT_FILENO);
dup2(fd, STDERR_FILENO);
execl("hello_world", NULL);
close(fd);
return 0;
}
#include <stdio.h>
int main()
{
printf("Hello World!\n");
return 0;
}
After I run example 1, my console shows:
test1
How do I change example 2 to redirect the printf() to console? Thank you.
