250+ TOP MCQs on Unix Domain Sockets and Answers [2024]

Linux Debugging questions and answers focuses on Unix Domain Sockets.1. What is the output of this program?

```
   #include
```
```
   int main()
```
```
   {
```
```
       int fd_socket;
```

       fd_socket = socket(AF_UNIX,SOCK_STREAM,0);

```
       printf("%dn",fd_socket);
```
```
       return 0;
```
```
   }
```

a) -1
b) 0
c) any integer value
d) none of the mentioned

Answer: d

2. In this program, the third argument of the socket() is used for _____ potocol.

```
   #include
```
```
   #include<sys/types.h>
```
```
   #include<sys/socket.h>
```
```
   int main()
```
```
   {
```
```
       int fd_socket;
```

       if(socket(AF_UNIX,SOCK_STREAM,0) == -1)

```
           perror("socket");
```
```
       return 0;
```
```
   }
```

a) TCP/IP
b) UDP
c) both TCP/IP and UDP
d) none of mentioned

Answer: a
Clarification: None.

3. By this program the soket “san_sock” will create

```
   #include
```
```
   #include<sys/types.h>
```
```
   #include<sys/un.h>
```
```
   #include<sys/socket.h>
```
```
   int main()
```
```
   {
```
```
       struct sockaddr_un add_server;
```
```
       int fd_server;
```

       fd_server = socket(AF_UNIX,SOCK_STREAM,0);

```
       if(fd_server == -1)
```
```
           perror("socket");
```
```
       add_server.sun_family = AF_UNIX;
```

       strcpy(add_server.sun_path,"san_sock");

       if( bind(fd_server,(struct sockaddr*)&add_server,sizeof(add_server)) != 0)

```
           perror("bind");
```
```
       return 0;
```
```
   }
```

a) in the /tmp directory
b) in the /usr directory
c) in the present working directory
d) none of the mentioned

Answer: c

4. What is the length of of the queue for pending connections in this program?

```
   #include
```
```
   #include<sys/types.h>
```
```
   #include<sys/un.h>
```
```
   #include<sys/socket.h>
```
```
   int main()
```
```
   {
```
```
       struct sockaddr_un add_server;
```
```
       int fd_server;
```

       fd_server = socket(AF_UNIX,SOCK_STREAM,0);

```
       if(fd_server == -1)
```
```
           perror("socket");
```
```
       add_server.sun_family = AF_UNIX;
```

       strcpy(add_server.sun_path,"server_sock2");

       if( bind(fd_server,(struct sockaddr*)&add_server,sizeof(add_server)) != 0)

```
           perror("bind");
```
```
       if( listen(fd_server,3) != 0)
```
```
           perror("listen");
```
```
       return 0;
```
```
   }
```

a) 0
b) 1
c) 2
d) 3

Answer: d
Clarification: The second argument of listen() specifies the length for the queue for pending connections.

5. What is the output of the program?

```
   #include
```
```
   #include<sys/types.h>
```
```
   #include<sys/un.h>
```
```
   #include<sys/socket.h>
```
```
   int main()
```
```
   {
```

       struct sockaddr_un add_server, add_client;

```
       int fd_server, fd_client;
```
```
       int len;
```
```
       char ch;
```

       fd_server = socket(AF_UNIX,SOCK_STREAM,0);

```
       if(fd_server == -1)
```
```
           perror("socket");
```
```
       add_server.sun_family = AF_UNIX;
```

       strcpy(add_server.sun_path,"san_sock");

       if( bind(fd_server,(struct sockaddr*)&add_server,sizeof(add_server)) != 0)

```
           perror("bind");
```
```
       if( listen(fd_server,3) != 0)
```
```
           perror("listen");
```
```
       len = sizeof(add_client);
```

       fd_client = accept(fd_server,(struct sockaddr*)&add_client,&len);

```
       printf("n");
```
```
       return 0;
```
```
   }
```

a) the program will print the string “”
b) the process will remain block
c) segmentation fault
d) none of the mentioned

Answer: b

6. What is the output of this program?

```
   #include
```
```
   #include<sys/types.h>
```
```
   #include<sys/socket.h>
```
```
   int main()
```
```
   {
```
```
       int fd;
```

       fd = socket(AF_UNIX,SOCK_STREAM,0);

```
       printf("%dn",fd);
```
```
       return 0;
```
```
   }
```

a) 0
b) 1
c) 2
d) 3

Answer: d

7. What is the output of this program?

```
   #include
```
```
   #include<sys/types.h>
```
```
   #include<sys/un.h>
```
```
   #include<sys/socket.h>
```
```
   #include
```
```
   int main()
```
```
   {
```
```
       struct sockaddr_un addr;
```
```
       int fd;
```

       fd = socket(AF_UNIX,SOCK_STREAM,0);

```
       if (fd == -1)
```
```
           perror("socket");
```
```
       addr.sun_family = AF_UNIX;
```

       strcpy(addr.sun_path,"san_sock");

       if (bind(4,(struct sockaddr*)&addr,sizeof(addr)) == -1)

```
           printf("Sanfoudnryn");
```
```
       return 0;
```
```
   }
```

a) this program will print the string “”
b) this program will not print the string “”
c) segmentation fault
d) none of the mentioned

Answer: a

8. What this program is not able to connect with any client program?

```
   #include
```
```
   #include<sys/types.h>
```
```
   #include<sys/un.h>
```
```
   #include<sys/socket.h>
```
```
   int main()
```
```
   {
```

       struct sockaddr_un add_server, add_client;

```
       int fd_server, fd_client;
```
```
       int len;
```
```
       char ch;
```

       fd_server = socket(AF_UNIX,SOCK_STREAM,0);

```
       if(fd_server == -1)
```
```
           perror("socket");
```
```
       add_server.sun_family = AF_UNIX;
```

       strcpy(add_server.sun_path,"san_sock");

       if( bind(fd_server,(struct sockaddr*)&add_server,sizeof(add_server)) != 0)

```
           perror("bind");
```
```
       len = sizeof(add_client);
```

       fd_client = accept(fd_server,(struct sockaddr*)&add_client,&len);

```
       printf("n");
```
```
       return 0;
```
```
   }
```

a) the listen() is missing
b) the connect() is missing
c) the read() and write() are missing
d) none of the mentioned

Answer: a
Clarification: None.

9. What is the output of this program?

```
   #include
```
```
   #include<sys/types.h>
```
```
   #include<sys/un.h>
```
```
   #include<sys/socket.h>
```
```
   int main()
```
```
   {
```

       struct sockaddr_un add_server, add_client;

```
       int fd_server, fd_client;
```
```
       int len;
```
```
       char ch;
```

       fd_server = socket(AF_UNIX,SOCK_STREAM,0);

```
       if(fd_server == -1)
```
```
           perror("socket");
```
```
       add_server.sun_family = AF_UNIX;
```

       strcpy(add_server.sun_path,"san_sock");

       if( bind(fd_server,(struct sockaddr*)&add_server,sizeof(add_server)) != 0)

```
           perror("bind");
```
```
       len = sizeof(add_client);
```

       fd_client = connect(fd_server,(struct sockaddr*)&add_client,&len);

```
       printf("n");
```
```
       return 0;
```
```
   }
```

a) this program will print the string “”
b) segmentation fault
c) error
d) none of the mentioned

Answer: c

10. What is the output of this program?

```
    #include
```
```
    #include<sys/types.h>
```
```
    #include<netinet/in.h>
```
```
    #include<sys/socket.h>
```
```
    #include
```
```
    int main()
```
```
    {
```
```
        struct sockaddr_in addr;
```
```
        int fd;
```

        fd = socket(AF_UNIX,SOCK_STREAM,0);

```
        if (fd == -1)
```
```
            perror("socket");
```
```
        addr.sun_family = AF_UNIX;
```

        strcpy(addr.sun_path,"san_sock");

        if (bind(4,(struct sockaddr*)&addr,sizeof(addr)) == -1)

```
            printf("Sanfoudnryn");
```
```
        return 0;
```
```
    }
```

a) error
b) “”
c) segmentation fault
d) none of the mentioned

Answer: a

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