The daemon program is associated with a message queue with a predefined key, to be blocked later when waiting for messages.
The two programs implement a producer-consumer problem.
The process sends a message to the queue, and the daemon wakes up to write the message it receives in a file.
daemon creates a queue and sends a message to the message queue. The daemon runs for 10 seconds and stops
How can I improve the program? Please criticize the implementation
daemon:
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <signal.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <syslog.h>
#include <time.h>
#include <sys/ipc.h>
#include <sys/msg.h>
#define MSGSZ 128
// Declare the message structure.
typedef struct msgbuf {
long mtype;
char mtext[MSGSZ];
} message_buf;
static void skeleton_daemon()
{
pid_t pid;
pid = fork();
printf(" fork pid=%d\n",pid);
if (pid < 0){
printf("fail fork\n");
exit(EXIT_FAILURE);}
if (pid > 0){
printf(" succes exit parent pid=%d\n",pid);
exit(EXIT_SUCCESS);}
if (setsid() < 0){
printf(" child fail\n");
exit(EXIT_FAILURE);}
// Catch, ignore and handle signals
// Implement a working signal handler
signal(SIGCHLD, SIG_IGN);
signal(SIGHUP, SIG_IGN);
// Fork
pid = fork();
/* daca error */
if (pid < 0){
printf(" child 2 fail\n");
exit(EXIT_FAILURE);}
if (pid > 0){
printf(" child 2 succes, parent exit pid=%d\n",pid);
exit(EXIT_SUCCESS);}
// Set new file permissions
umask(0);
// Change the working directory to the root directory
// or another appropriated directory
//chdir("/");
// Close all open file descriptors
int x;
for (x = sysconf(_SC_OPEN_MAX); x>=0; x--)
{
close (x);
}
}
int main()
{
time_t T = time(NULL);
skeleton_daemon();
FILE *fp;
char *timp;
char *sir;
while (1)
{
int msqid;
key_t key;
message_buf rbuf;
key = 1234;
if ((msqid = msgget(key, 0666)) >= 0) {
// Incoming message type 1.
if (msgrcv(msqid, &rbuf, MSGSZ, 1, 0) >= 0) {
timp = ctime(&T);
fp = fopen( "file.txt" , "a" );
fwrite( timp, 1 , 24 , fp );
sir = rbuf.mtext;
fwrite( sir , 1 , sizeof(sir) , fp );
fclose(fp);
}
}
// code demon.
sleep (10);
break;
}
T = time(NULL);
timp = ctime(&T);
char str[] = " daemon finished. \n";
fp = fopen( "file.txt" , "a" );
fwrite( timp, 1 , 24 , fp );
fwrite(str , 1 , sizeof(str) -1, fp );
fclose(fp);
// message failure, can be read if demonization failed
printf(" this is not a demon\n");
return EXIT_SUCCESS;
}
sender:
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/msg.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#define MSGSZ 128
// The structure of the message is declared
typedef struct msgbuf {
long mtype;
char mtext[MSGSZ];
} message_buf;
main()
{
int msqid;
int msgflg = IPC_CREAT | 0666;
key_t key;
message_buf sbuf;
size_t buf_length;
key = 1234;
(void)fprintf(stderr, "\nmsgget: Calling msgget(%#1x,\%#o)\n", key, msgflg);
if ((msqid = msgget(key, 0666 | IPC_CREAT))){;//msgflg)) < 0) {
perror("msgget");
exit(1);
}
else
(void)fprintf(stderr, "msgget: msgget succeeded: msgqid = %d\n", msqid);
// The type 1 message is being sent
sbuf.mtype = 1;
(void) fprintf(stderr, "msggeet: msgget succeeded: msqid = %d\n", msqid);
(void) strcpy(sbuf.mtext, "Did you get this?");
(void) fprintf(stderr, "msgget: msgget succeeded: msqid = %d\n", msqid);
buf_length = strlen(sbuf.mtext) + 1;
//The message is being sent.
if((msgsnd(msqid, &sbuf, buf_length, IPC_NOWAIT)) < 0){
printf("%d, %d, %s, %d\n", msqid, sbuf.mtype, sbuf.mtext, buf_length);
perror("msgsnd");
exit(1);
}
else
printf("Message: \"%s\" Sent\n", sbuf.mtext);
exit(0);
}
```
