Re: [PATCH v2] msgop.2: add an example program

["Michael Kerrisk (man-pages)" <mtk.manpages-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

Hi Bill,

On 03/05/2015 02:31 AM, wfp5p-rupya+Y+cgAvmQRmTv5wTA@public.gmane.org wrote:
> From: Bill Pemberton <wfp5p-rupya+Y+cgAvmQRmTv5wTA@public.gmane.org>

Looks good! Applied. Thanks very much for the patch!

Cheers,

Michael

> Signed-off-by: Bill Pemberton <wfp5p-rupya+Y+cgAvmQRmTv5wTA@public.gmane.org>
> ---
>  man2/msgop.2 | 140 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 138 insertions(+), 2 deletions(-)
> 
> diff --git a/man2/msgop.2 b/man2/msgop.2
> index d1bd2125344d..2546d241e960 100644
> --- a/man2/msgop.2
> +++ b/man2/msgop.2
> @@ -36,8 +36,6 @@
>  .\"	Language and formatting clean-ups
>  .\"	Added notes on /proc files
>  .\"
> -.\" FIXME Add example programs to this page.
> -.\"
>  .TH MSGOP 2 2015-02-21 "Linux" "Linux Programmer's Manual"
>  .SH NAME
>  msgrcv, msgsnd \- System V message queue operations
> @@ -578,6 +576,144 @@ this error was not diagnosed by
>  This bug is fixed
>  .\" commit 4f87dac386cc43d5525da7a939d4b4e7edbea22c
>  in Linux 3.14.
> +.SH EXAMPLE
> +The program below demonstrates the use of
> +.BR msgsnd ()
> +and
> +.BR msgrcv ().
> +
> +The example program is first run with the \fB\-s\fP option to send a
> +message and then run again with the \fB-r\fP option to receive a
> +message.
> +
> +The following shell session shows a sample run of the program:
> +.in +4n
> +.nf
> +
> +.RB "$" " ./a.out \-s"
> +sent: a message at Wed Mar  4 16:25:45 2015
> +
> +.RB "$" " ./a.out \-r"
> +message received: a message at Wed Mar  4 16:25:45 2015
> +
> +.fi
> +.in
> +.SS Program source
> +\&
> +.nf
> +/* msgop.c */
> +
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <time.h>
> +#include <unistd.h>
> +#include <errno.h>
> +#include <sys/types.h>
> +#include <sys/ipc.h>
> +#include <sys/msg.h>
> +
> +struct msgbuf {
> +    long mtype;
> +    char mtext[80];
> +};
> +
> +static void
> +usage(char *prog_name, char *msg)
> +{
> +    if (msg != NULL)
> +        fputs(msg, stderr);
> +
> +    fprintf(stderr, "Usage: %s [options]\\n", prog_name);
> +    fprintf(stderr, "Options are:\\n");
> +    fprintf(stderr, "\-s        send message using msgsnd()\\n");
> +    fprintf(stderr, "\-r        read message using msgrcv()\\n");
> +    fprintf(stderr, "\-t        message type (default is 1)\\n");
> +    fprintf(stderr, "\-k        message queue key (default is 1234)\\n");
> +    exit(EXIT_FAILURE);
> +}
> +
> +static void
> +send_msg(int qid, int msgtype)
> +{
> +    struct msgbuf msg;
> +    time_t t;
> +
> +    msg.mtype = msgtype;
> +
> +    time(&t);
> +    snprintf(msg.mtext, sizeof(msg.mtext), "a message at %s", ctime(&t));
> +
> +    if (msgsnd(qid, (void *) &msg, sizeof(msg.mtext), IPC_NOWAIT) == \-1) {
> +        perror("msgsnd error");
> +        exit(EXIT_FAILURE);
> +    }
> +    printf("sent: %s\\n", msg.mtext);
> +}
> +
> +static void
> +get_msg(int qid, int msgtype)
> +{
> +    struct msgbuf msg;
> +
> +    if (msgrcv(qid, (void *) &msg, sizeof(msg.mtext), msgtype,
> +               MSG_NOERROR | IPC_NOWAIT) == \-1) {
> +        if (errno != ENOMSG) {
> +            perror("msgrcv");
> +            exit(EXIT_FAILURE);
> +        }
> +        printf("No message available for msgrcv()\\n");
> +    } else
> +        printf("message received: %s\\n", msg.mtext);
> +}
> +
> +int
> +main(int argc, char *argv[])
> +{
> +    int qid, opt;
> +    int mode = 0;               /* 1 = send, 2 = receive */
> +    int msgtype = 1;
> +    int msgkey = 1234;
> +
> +    while ((opt = getopt(argc, argv, "srt:k:")) != \-1) {
> +        switch (opt) {
> +        case \(aqs\(aq:
> +            mode = 1;
> +            break;
> +        case \(aqr\(aq:
> +            mode = 2;
> +            break;
> +        case \(aqt\(aq:
> +            msgtype = atoi(optarg);
> +            if (msgtype <= 0)
> +                usage(argv[0], "\-t option must be greater than 0\\n");
> +            break;
> +        case \(aqk\(aq:
> +            msgkey = atoi(optarg);
> +            break;
> +        default:
> +            usage(argv[0], "Unrecognized option\\n");
> +        }
> +    }
> +
> +    if (mode == 0)
> +        usage(argv[0], "must use either \-s or \-r option\\n");
> +
> +    qid = msgget(msgkey, IPC_CREAT | 0666);
> +
> +    if (qid == \-1) {
> +        perror("msgget");
> +        exit(EXIT_FAILURE);
> +    }
> +
> +    if (mode == 2)
> +        get_msg(qid, msgtype);
> +    else
> +        send_msg(qid, msgtype);
> +
> +    exit(EXIT_SUCCESS);
> +}
> +.fi
>  .SH SEE ALSO
>  .BR msgctl (2),
>  .BR msgget (2),
> 


-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
--
To unsubscribe from this list: send the line "unsubscribe linux-man" in
the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html