POSIX message queue operate

1  mq_creat()

#include

 #include

 #include           /* For O_* constants */

 #include        /* For mode constants */

  #include

  #include

void perror(const char *s);

#include

extern int errno;

struct mq_attr attr;

 extern char *optarg;

 extern int optind, opterr, optopt;

 #define FILE_MODE  (S_IRUSR|S_IWUSR)   //注意这个宏，否则可能在调用mq_send()时permision denied.

int main(int argc,char **argv)

{

int c,flags;

mqd_t mqd ;

flags = O_RDWR | O_CREAT;

while((c = getopt(argc,argv,"em:z:"))!=-1){

switch(c)

{

case 'e':

flags |= O_EXCL;

break;

case 'm':

attr.mq_maxmsg = atoi(optarg);

attr.mq_msgsize = atoi(optarg);

break;

case 'z':

attr.mq_msgsize = atoi(optarg);

break;

}

}

if(optind != argc -1)

{fprintf(stdout," usage;\n");exit(1);}

 

if((attr.mq_maxmsg!=0&&attr.mq_msgsize == 0)||(attr.mq_maxmsg == 0 &&attr.mq_msgsize != 0))

{fprintf(stdout,"msgsize/maxmsg\n");exit(2);}

mqd = mq_open(argv[optind],flags,FILE_MODE,(attr.mq_maxmsg!=0)?(&attr):NULL);

if(-1==mqd)

{fprintf(stdout,"mq_open() error  :%s \n",strerror(errno));exit(1);}

mq_close(mqd);

exit(0);

}

 /*gcc  THIS_FILE  -lrt -o mq_creat*/

[jim@jim c]$ ./mq_creat -e -m 1024 -z 1024    /jim_mq

mq_open() error  :Invalid argument 

Invalid argument

[jim@jim c]$ ./mq_creat -e -m 1024 -z 1024    /mq

mq_open() error  :Invalid argument 

Invalid argument

//看来哪里有问题

man mq_overview

[jim@jim mqueue]$ pwd

/proc/sys/fs/mqueue

[jim@jim mqueue]$ cat msg_max 

10

[jim@jim mqueue]$ cat msgsize_max 

8192

[jim@jim mqueue]$ cat  queues_max 

256

[jim@jim c]$ ./mq_creat -e -m 6  -z 1024    /mq

[jim@jim c]$ echo $?

0  // seems OK now

2 mq_getattr()

#include

 #include

 #include           /* For O_* constants */

 #include        /* For mode constants */

  #include

struct mq_attr attr;

 extern char *optarg;

  extern int optind, opterr, optopt;

extern char * optarg;

extern int optind;

int main(int argc,char**argv)

{

mqd_t mqd;

struct mq_attr attr;

if(2!=argc)

{fprintf(stdout,"usage:%s ",argv[0]);}

mqd = mq_open(argv[1],O_RDONLY);

if(-1==mqd)

{fprintf(stdout,"mq_open() error \n");exit(1);}

mq_getattr(mqd,&attr);

fprintf(stdout,"max msgs = %ld,max #bytes/msg = %ld,#currently on queue = %ld\n",attr.mq_maxmsg,attr.mq_msgsize,attr.mq_curmsgs);/*fprintf(),vs printf()*/

mq_close(mqd);

exit(0);

}

/*gcc THIS_FILE -lrt -o mq_getattr*/

[jim@jim c]$ ./mq_getattr /mq

max msgs = 6,max #bytes/msg = 1024,#currently on queue = 0

3 mq_send()

#include

 #include

 #include           /* For O_* constants */

 #include        /* For mode constants */

  #include

  #include

void perror(const char *s);

#include

extern int errno;

struct mq_attr attr;

 extern char *optarg;

 extern int optind, opterr, optopt;

 #define FILE_MODE   (S_IRUSR|S_IWUSR)

int main(int argc,char **argv)

{

int c,flags;

mqd_t mqd ;

flags = O_RDWR | O_CREAT;

while((c = getopt(argc,argv,"em:z:"))!=-1){

switch(c)

{

case 'e':

flags |= O_EXCL;

break;

case 'm':

attr.mq_maxmsg = atoi(optarg);

attr.mq_msgsize = atoi(optarg);

break;

case 'z':

attr.mq_msgsize = atoi(optarg);

break;

}

}

if(optind != argc -1)

{fprintf(stdout," usage;\n");exit(1);}

 

if((attr.mq_maxmsg!=0&&attr.mq_msgsize == 0)||(attr.mq_maxmsg == 0 &&attr.mq_msgsize != 0))

{fprintf(stdout,"msgsize/maxmsg\n");exit(2);}

mqd = mq_open(argv[optind],flags,FILE_MODE,(attr.mq_maxmsg!=0)?(&attr):NULL);

if(-1==mqd)

{fprintf(stdout,"mq_open() error  :%s \n",strerror(errno));exit(1);}

mq_close(mqd);

exit(0);

}

 /*gcc  THIS_FILE  -lrt  -o mq_send*/