Msgget(2) returns 0 - a workaround fix Post: 302906930

Sponsored Content

Top Forums Programming Msgget(2) returns 0 - a workaround fix Post 302906930 by jim mcnamara on Tuesday 24th of June 2014 02:55:44 PM

06-24-2014

Registered User

msgid is NOT a message it is a message queue id. (A shared (IPC) memory object, not an individual message) A return of msgid ==0 means success. Any number >-1 == success.

Since you really did not post much code --
You should be calling msgrcv like this (note infinite loop is NOT required):

Code:

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/msg.h>

struct my_msgbuf 
{
 long mtype;
 char mtext[200];
};

int main(void)
{
   struct my_msgbuf buf;
   int msqid=0;
   key_t key;
   if ((key = ftok("[your key code goes here]", 'B')) =< -1)  /* same key as other program  edit:changed to =< */
   {
     perror("ftok");
     exit(1);
   }
   if ((msqid = msgget(key, 0666)) == -1)  /* connect to the queue */
   {
      perror("msgget");
      exit(1);
   }
   printf("Ready to receive messages\n");
   for(;;) 
   { 
      if (msgrcv(msqid, &buf, sizeof(buf.mtext), 0, 0) == -1)
      {
        perror("msgrcv");
        exit(1);
      }
      printf("%s\n", buf.mtext);
   }
   return 0;
}

The above snippet works correctly, I use it in other code....

Last edited by jim mcnamara; 06-24-2014 at 11:25 PM..

This User Gave Thanks to jim mcnamara For This Post:

jim mcnamara

View Public Profile for jim mcnamara

Find all posts by jim mcnamara

9 More Discussions You Might Find Interesting

1. Programming

about msgget troble

hi,all i have in trouble about msgget. i create a queue and the program like blow: openMsg( pid_t key ) { .... int msgid; .... msgid=msgget(key,IPC_CREAT|IPC_EXCL|0666) if( msgid<=0 ){ fprintf( stdout,"%s,%d",strerror(errno),errno ); return -1; ...

2. Shell Programming and Scripting

find & sed -i work fine. Now need -i workaround for old OS.

I have a script that does a search and replace on a tree using find, xargs and sed that looks something like this. find . -type f -print0 | xargs -0 sed -i 's/fromthis/tothis/g' Now this works fine on new versions on Linux but I need to make the script work on an old RAQ550 that has an older...

3. Programming

Problem with msgget()

Hi, I am having problem with msgget() function. Here is the problem that I am having on Unix : I have two processes sender and receiver. Sender generates queue (msgget()) with some key e.g. 938, for output. Receiver reads from the same queue. i.e. receiver also tries to get queue...

4. UNIX for Dummies Questions & Answers

Workaround for macros in sftp command

Hi, I've some existing scripts wherein am using ftp + .netrc. I've defined my macros in .netrc file. I want to switch to sftp now but it seems it doesn't support macros and .netrc and it gives "command invalid" error. Is there any other alternative? Note: I don't want help for...

5. Windows & DOS: Issues & Discussions

Samba trouble shoot / workaround ?

Hello, I've setup a ubuntu 10.04 server running samba 3.4.7 as domain controler / file server at a customer site, that works great most of the time but I face a random problem. Of course I'm never on the site when the problem occurs, so I cannot investigate in real time. What happens is that...

6. Shell Programming and Scripting

Calculation returns no value

#/bin/sh ..... #convert memory to MB let "mmsize_a= ($mmsize)/256" let "mminuse_a= ($mminuse)/256" let "mmfree_a= ($mmsize_a -$mminuse_a)" let "mmfreepercent= (($mmfree_a)/($mmsize_a))*100" # #format output echo "\n\n######################" >>$sndFile echo "\n$sysName Total Memory usage"...

7. Programming

msgget message queue always get permission denied

I want to use msgget() to obtain a message queue between two processes, here is my code: the first one create the mq, the second one open it and add a message to it. But when I execute the second one, I get permission denied. I've already desperately tried everything I can think of to solve this...

8. UNIX for Advanced & Expert Users

stuck in CLOSE_WAIT Solaris 10 - Patch and workaround

Solaris 10 Sparc: When you got a connection locking a tcp/port, and the status is CLOSE_WAIT (for ever :wall:), you just use the tcpdrop, to close the connection. This is a OS bug. I wrote the bug id bellow: BUG-ID 6468753 connections stuck in CLOSE_WAIT The patch that's correct the bug:...

9. AIX

AIO workaround AIX 5.3 to AIX 7.1

Hello Folks, Facing a problem starting Apache Services on AIX 7.1 This is the error i'm getting /oraapp/prodora/iAS/Apache/Apache/bin/apachectl start: httpd started Syntax error on line 17 of /oraapp/prodora/iAS/Apache/modplsql/cfg/plsql_pls.conf: Cannot load...

LEARN ABOUT OPENSOLARIS

msgget

msgget(1)							   User Commands							 msgget(1)

NAME

       msgget - get a message from a message catalog

SYNOPSIS

       msgget locale [command:]catalog [set.]number [text]

DESCRIPTION

       msgget gets the message corresponding to the parameters. See OPERANDS.

OPERANDS

       The following operands are supported:

       catalog	       Specifies the message catalog name.

       command	       Specifies command-specific message.

       locale	       Specifies the locale. If locale is - then the current locale is used.

       [set].number    Identifies  the	message  by message number and an optional message set. If specified as - , the message set and number are
		       determined by looking up text in the corresponding C locale message catalog.

       text	       Specifies the text of the message to be output upon error.

EXIT STATUS

       0     Successful completion.

       >0    An error occurred.

EXAMPLES

       Example 1 Getting a Message in the Current Locale

       The following example gets msg 1 in the current locale from message catalog hello:

	 example% msgget - hello 1
	 hello world

AUTHORS

       Glenn Fowler, gsf@research.att.com

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Availability		     |SUNWastdev		   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Volatile			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       iconv(1), msgcc(1), msggen(1), attributes(5)

SunOS 5.11							    9 Oct 2007								 msgget(1)