c - 中断阻塞读

Question

我的程序经历了这样一个循环:

...
while(1){
  read(sockfd,buf,sizeof(buf));
  ...
}

read 函数在等待输入时阻塞，而输入恰好来自套接字。我想处理 SIGINT 并基本上告诉它在读取时停止读取函数，然后调用任意函数。执行此操作的最佳方法是什么？

Answer 1

来自 read(2):

   EINTR  The call was interrupted by a signal before any data
          was read; see signal(7).

如果您修改代码使其看起来更像:

cont = 1;
while (1 && cont) {
    ret = read(sockfd, buf, sizeof(buf));
    if (ret < 0 && errno == EINTR)
        cont = arbitrary_function();
}

这让 arbitrary_function() 决定是否应该重试 read(2)。

更新

您需要处理信号以便从 read(2) 获得 EINTR 行为:

#include<unistd.h>
#include<stdio.h>
#include<stdlib.h>
#include<signal.h>
#include<errno.h>

int interrupted;

void handle_int(int num) {
  interrupted = 1;
}

int main(void){
  char buf[9001];
  struct sigaction int_handler = {.sa_handler=handle_int};
  sigaction(SIGINT,&int_handler,0);
  while(!interrupted){
    printf("interrupted: %d\n", interrupted);
    if(read(0,buf,sizeof(buf))<0){
      if(errno==EINTR){
        puts("eintr");
      }else{
        printf("%d\n",errno);
      }
      puts(".");
    }
  }
  puts("end");
  return 0;
}

给出输出:

$ ./foo
interrupted: 0
hello
interrupted: 0
^Ceintr
.
end