msgget.c

msgget函数的使用例子

/*
 * msgget.c: Illustrate the msgget() function.
 * This is a simple exerciser of the msgget() function. It prompts
 * for the arguments, makes the call, and reports the results. 
 */

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

extern void  exit();
extern void  perror();

main(){
	key_t	key;  /* key to be passed to msgget() */
	int		msgflg,  /* msgflg to be passed to msgget() */
			msqid;  /* return value from msgget() */ 
	
	(void) fprintf(stderr,"All numeric input is expected to follow C conventions:\n");
	(void) fprintf(stderr,  "\t0x... is interpreted as hexadecimal,\n");
	(void) fprintf(stderr, "\t0... is interpreted as octal,\n");
	(void) fprintf(stderr, "\totherwise, decimal.\n");
	(void) fprintf(stderr, "IPC_PRIVATE == %#lx\n", IPC_PRIVATE);
	(void) fprintf(stderr, "Enter key: "); (void) scanf("%li", &key);
	(void) fprintf(stderr, "\nExpected flags for msgflg argumentare:\n");
	(void) fprintf(stderr, "\tIPC_EXCL =\t%#8.8o\n", IPC_EXCL);
	(void) fprintf(stderr, "\tIPC_CREAT =\t%#8.8o\n", IPC_CREAT);
	(void) fprintf(stderr, "\towner read =\t%#8.8o\n", 0400);
	(void) fprintf(stderr, "\towner write =\t%#8.8o\n", 0200);
	(void) fprintf(stderr, "\tgroup read =\t%#8.8o\n", 040);
	(void) fprintf(stderr, "\tgroup write =\t%#8.8o\n", 020);
	(void) fprintf(stderr, "\tother read =\t%#8.8o\n", 04);
	(void) fprintf(stderr, "\tother write =\t%#8.8o\n", 02);
	(void) fprintf(stderr, "Enter msgflg value: "); (void) scanf("%i", &msgflg);
	(void) fprintf(stderr, "\nmsgget: Calling msgget(%#lx,%#o)\n", key, msgflg);
	
	if ((msqid = msgget(key, msgflg)) == -1) {
		perror("msgget: msgget failed");
		exit(1); 
	} else {  
		(void) fprintf(stderr,
		"msgget: msgget succeeded: msqid = %d\n", msqid);  
		exit(0); 
	}
}