Linux被中断的系统如何调用详解

#include 
#include 
#include 
#include 

void handler(int s)
{
  printf("read is interrupt by signal handler\n");
  return;
}

int main()
{
  char buf[10];
  int nread = 0;

  signal(SIGALRM, handler);
  alarm(2);

  printf("read start\n");
  nread = read(STDIN_FILENO, buf, sizeof(buf));
  printf("read return\n");

  if ((nread <0) && (errno == EINTR))
  {
    printf("read return failed, errno is EINTR\n");
  }

  return 0;
}

#include 
#include 
#include 
#include 

void handler(int s)
{
  printf("read is interrupt by signal handler\n");
  return;
}

int main()
{
  char buf[10];
  int nread = 0;
  struct sigaction act;

  sigemptyset(&act.sa_mask);
  act.sa_handler = handler;
  act.sa_flags = 0; //不给SIGALRM信号设置SA_RESTART标志，使用sigaction的默认处理方式
  //act.sa_flag |= SA_INTERRUPT; //SA_INTERRUPT是sigaction的默认处理方式，即不自动重启被中断的系统调用
  //实际上，不管act.sa_flags值为多少，只要不设置SA_RESTART，sigaction都是按SA_INTERRUPT处理的

  sigaction(SIGALRM, &act, NULL);
  alarm(2);

  printf("read start\n");
  nread = read(STDIN_FILENO, buf, sizeof(buf));
  printf("read return\n");

  if ((nread <0) && (errno == EINTR))
  {
    printf("read return failed, errno is EINTR\n");
  }

  return 0;
}

#include 
#include 
#include 
#include 

void handler(int s)
{
  printf("read is interrupt by signal handler\n");
  return;
}

int main()
{
  char buf[10];
  int nread = 0;
  struct sigaction act;

  sigemptyset(&act.sa_mask);
  act.sa_handler = handler;
  act.sa_flags = 0;
  act.sa_flags |= SA_RESTART; //给SIGALRM信号设置SA_RESTART标志

  sigaction(SIGALRM, &act, NULL);
  alarm(2);

  printf("read start\n");
  nread = read(STDIN_FILENO, buf, sizeof(buf));
  printf("read return\n");

  if ((nread <0) && (errno == EINTR))
  {
    printf("read return failed, errno is EINTR\n");
  }

  return 0;
}

int nread = read(fd, buf, 1024);

if (nread <0)
{
  if (errno == EINTR)
  {
    //read被中断，其实不应该算作失败，可以根据实际需求进行处理，比如重写调用read，也可以忽略它
  }
  else
  {
    //read真正的读错误
  }
}