Linux Message Queue Question!!!

This is a discussion on Linux Message Queue Question!!! within the Linux Programming forums, part of the Platform Specific Boards category; In the code below I simply want to send a message to an message queue. and output the number of ...

  1. #1
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    Question Linux Message Queue Question!!!

    In the code below I simply want to send a message to an message queue. and output the number of messages in the queue. But the output is 0.....

    could any one provide a solution to this so that once I send a message to the queue, the queue size++?

    Thanks very much!!!

    Code:
    #include <stdio.h>
    #include <stdlib.h>
    #include <linux/ipc.h>
    #include <linux/msg.h>
    #include <sys/types.h>
    #include <wait.h>
    #include <unistd.h>
    #include <errno.h>
    
    typedef struct
    {
      long mtype;
      int veh_type;//1: car, 2: truck
      int pid; //msg id
    } msg;
    
    main()
    {    msg message;
        message.mtype=1;
        message.veh_type=0;
        message.pid=0;
    
        int qid=msgget(111,IPC_CREAT|0666);
        msgsnd(qid,&message,sizeof(msg),0);
    
        struct msqid_ds buf;
      
        msgctl(qid,IPC_STAT,&buf);
        int result=buf.msg_qnum;
        printf("%d\n",result);
        msgctl(qid,IPC_RMID,0);
    }

  2. #2
    and the hat of wrongness Salem's Avatar
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    All the functions return a success/fail status.

    Perhaps you can begin with checking those things.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
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