pgm_ipc_msgq_client.c

Linux MessageQueue Sample code

     /*  CLIENT ... sends messages to the server  */ 
	#include "local.h" 
	#include <cstdio> 
	using namespace std; 
	int 	main( )
	{ 
		key_t       key; 
		pid_t       cli_pid; 
		int         mid, n; 
		MESSAGE     msg; 
		static char m_key[10]; 
		cli_pid = getpid( ); 
		if ((key = ftok(".", SEED)) == -1) 
		{ 
			perror("Client: key generation"); 
			return 1; 
		} 
		if ((mid=msgget(key, 0 )) == -1 ) 
		{        
			mid = msgget(key,IPC_CREAT | 0660); 
			switch (fork())
			{ 
				case -1: 
				  perror("Client: fork"); 
				  return 2; 
				case 0: 
				  sprintf(m_key, "%d", mid);            
				  execlp("./server", "server", m_key, "&", 0); 
				  perror("Client: exec"); 
				  return 3; 
			} 
		} 
		while (1) 
		{ 
			msg.msg_to = SERVER; 
			msg.msg_fm = cli_pid;                    
			write(fileno(stdout), "cmd> ", 6); 
			memset(msg.buffer, 0x0, BUFSIZ); 
			if ( (n=read(fileno(stdin), msg.buffer, BUFSIZ)) == 0 ) 
			  break; 
			n += sizeof(msg.msg_fm);              
			if (msgsnd(mid, &msg, n, 0) == -1 ) 
			{ 
				  perror("Client: msgsend"); 
				  return 4; 
			} 
			if( (n=msgrcv(mid, &msg, BUFSIZ, cli_pid, 0)) != -1 ) 
				 write(fileno(stdout), msg.buffer, n);   
		} 
		msgsnd(mid, &msg, 0, 0); 
		return 0; 
       }