如何从 C 中的 stdin 进行非阻塞输入 [英] How to do nonblocking input from stdin in C

问题描述

我有以下情况我有一个程序连续对文件进行一组操作，我想在按下特定键时停止并执行另一组操作.

I have follow situation I have an program make an set of operations on a file continuously and I want, when a specific key is pressed, to stop and do another set of operations.

为此，我尝试使用带有

For this I tryed use scanf of an character with

fcntl(0, F_SETFL, O_NONBLOCK);

和

while(feof(stdin))

但它没有按预期工作.

我已经搜索过，有些地方有人说要使用 select，但我找不到如何使用它.

I have searched and in some places someone says to use select but I can't find how to use it.

有人可以以某种方式给我建议吗?

Anyone can advice me somehow?

我提供更多信息的主要功能:

my main function to provide more information:

int main(int argc, char *argv[])
{


 if(argc>1){
  char* password;
  char* password2;

  printf("Password? ");
  password = get_password();
  printf("Repita a password? ");
  password2 = get_password();

  if(strcmp(password,password2)!=0){
   printf("Passwords diferentes!\n");
   exit(1);
  }

  FILE *fptr;
  fptr = fopen("./regist", "r");
  if(fptr == NULL) //if file does not exist, create it
  {
   fptr = fopen("./regist", "w");
  }
  fclose(fptr);

  if(find_username(argv[1])){
   printf("Utilizador ja existe\n");
   exit(1);
  }
  add_user_regist(argv[1],password);
  printf("Utilizador %s adicionado.\n",argv[1]);
  exit(0);
 }


 char readbuf[250];

 /* Create the FIFO if it does not exist */
 umask(0);
 mknod(FIFO_FILE, S_IFIFO|0666, 0);
 printf("Servidor iniciado.\nEm modo de espera de mensagens\n");

 fcntl(0, F_SETFL, O_NONBLOCK);
 while(1){


  char c = getchar();
  if(c=='q' || c=='Q')
    exit(0);//by now only goes out


  fp = fopen(FIFO_FILE, "r");
  fgets(readbuf, 250, fp);
  fclose(fp);

  if(readbuf[0]=='U')
    user_access(readbuf);
  else if(readbuf[0]=='W')
    who_online(readbuf);
  else if(readbuf[0]=='R'){
    char* tmp;
    strtok(readbuf,":");
    tmp = strtok(NULL,";");
    remove_online(tmp);
    printf("# %s fez logout\n",tmp);
  }
  else if(readbuf[0]=='F'){
    process_msg(readbuf);
  }

 }
 return(0);
}

推荐答案

使用 GNU 阅读线:

#include <readline/readline.h>
#include <stdio.h>

static int func(int count, int key)
{
    printf ("key pressed: %c\n", key); /* exec your function */
    return 0;
}

int main(void)
{
    char *line;

    rl_bind_key('x', func); /* 'x' is the specific key */
    line = readline ("> ");
    printf("%s\n", line);
    return 0;
}

使用-lreadline

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