You can use the fcntl function to change the properties of an open file, and you can reset the flags such as read, write, append, and non-blocking (these flags are called File StatusFlag) without having to re-open the file.
The following example uses the fcntl commands F_GETFL and F_SETFL to change the attributes of STDIN_FILENO and the O_NONBLOCK option to implement the function of non-blocking read terminals.
#include <unistd.h>
#include <fcntl.h>
int fcntl(int fd, int cmd, ... /* arg */ );
Function:
Change file attribute
parameters:
fd: file descriptor
cmd: set command
F_GETFL
F_SETFL
arg: optional, determined by the second parameter, such as no when get, there is a value when set
Return value:
file status flag
-1: failure
step:
int flag; // file status flag
flag = fcntl( sockfd, F_GETFL, 0); //read
flag |= O_NONBLOCK;//change
fcntl(sockfd, F_SETFL, flag);//写
#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
intmain()
{
char buf[32] = {0};
#if 1
int flag;
flag = fcntl(0, F_GETFL, 0);
flag |= O_NONBLOCK;
fcntl(0, F_SETFL, flag);
#endif
while(1)
{
gets(buf);
printf("quit block\n");
puts(buf);
sleep(1);
}
}
The running result is as follows:
