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Archive for February 16th, 2012

APUE2e Exercise 10.6 – Solution C

February 16th, 2012 No comments

Using Standard I/O Library to read and write the file. Rather than using signal function, I used sigaction. Thus don’t need to call TELL_WAIT in the for body.

?Download exercise10-6c.c
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/**   
 * apue-chap10: exercise10-6c.c
 *
 * Description: Standard I/O Library + sigaction
 *
 * Created On: Feb 16, 2012 
 *
 * @author: Huang Zhu
 *
 * @email: zhuhuang.zp@gmail.com
 */
 
#include <apueerr.h>
#include <signal.h>
#include <stdio.h>
#include <fcntl.h>
 
#define __USE_POSIX199309	1
 
static volatile sig_atomic_t sigflag;
static sigset_t newmask, oldmask, zeromask;
 
struct sigaction act, oact1, oact2;
 
static void sig_usr(int signo)
{
	sigflag = 1;
}
 
void TELL_WAIT(void)
{
	act.sa_handler = sig_usr;
	sigemptyset(&act.sa_mask);
	act.sa_flags = 0;
 
	if(sigaction(SIGUSR1, &act, &oact1) < 0)
		err_sys("sigaction SIGUSR1 error");
 
	if(sigaction(SIGUSR2, &act, &oact2) < 0)
		err_sys("sigaction SIGUSR2 error");
 
	sigemptyset(&zeromask);
	sigemptyset(&newmask);
	sigaddset(&newmask, SIGUSR1);
	sigaddset(&newmask, SIGUSR2);
 
	//block SIGUSR1 and SIGUSR2, and save current signal mask
	if(sigprocmask(SIG_BLOCK, &newmask, &oldmask) < 0)
		perror("SIG_BLOCK error");
}
 
void TELL_PARENT(pid_t pid)
{
	kill(pid, SIGUSR2);
}
 
void TELL_CHILD(pid_t pid)
{
	kill(pid, SIGUSR1);
}
 
void WAIT_PARENT(void)
{
	while(sigflag == 0)
		sigsuspend(&zeromask);  //set mask and sleep and wait
	sigflag = 0;
 
	if(sigprocmask(SIG_SETMASK, &oldmask,  NULL) < 0)
		perror("SIG_SETMASK error");
}
 
void WAIT_CHILD(void)
{
	while(sigflag == 0)
		sigsuspend(&zeromask);  //set mask and sleep and wait
	sigflag = 0;
 
	if(sigprocmask(SIG_SETMASK, &oldmask,  NULL) < 0)
		perror("SIG_SETMASK error");
}
 
int main(void)
{
	int fd, pid, ppid, counter, round = 5;
	FILE* fp;
	char *filename = "counter.file";
	int i, j;
 
	if((fd = open(filename, O_RDWR | O_CREAT | O_TRUNC | O_SYNC, S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH)) < 0)
		err_sys("open error");
 
	if((fp = fdopen(fd, "r+")) == NULL )
		err_sys("fdopen error");
 
	if(fputc(0, fp) != EOF){
		printf("Writing initial value of the counter: 0\n");
		fflush(fp); //if fflush is not used, the change of counter cannot be seen instantly by other readers.
	}
 
	if(ferror(fp))
		err_sys("fputc error");
 
	TELL_WAIT();
 
	if((pid = fork()) < 0){
		err_sys("fork error");
	}else if(pid == 0){ //child
		ppid = getppid();
 
		for(i = 0;  i < round; i++){
			printf("\nChild: round %d\n", i+1);
			counter = -1;
 
			rewind(fp);
			counter = fgetc(fp);
			printf("Child: read counter from the file: %d\n", counter);
 
			counter++;
			printf("Child: increase counter to: %d\n", counter);
 
			rewind(fp);
			if(fputc(counter, fp) != EOF){
				printf("Child: Write counter to the file: %d\n", counter);
				fflush(fp);
			}
			if(ferror(fp))
				err_sys("Child: fputc error");
 
			TELL_PARENT(ppid);
 
			WAIT_PARENT();
		}
 
		counter = -1;
		rewind(fp);
		counter = fgetc(fp);
		printf("\nChild: read counter from the file: %d\n", counter);
 
		exit(0);
	}else{ //parent
		for(j = 0; j < round; j++){
			WAIT_CHILD();
			printf("\nParent: round %d\n", j+1);
			counter = -1;
 
			rewind(fp);
			counter = fgetc(fp);
			printf("Parent: read counter from the file: %d\n", counter);
 
			counter++;
			printf("Parent: increase counter to: %d\n", counter);
 
			rewind(fp);
			if(fputc(counter, fp) != EOF){
				printf("Parent: Write counter to the file: %d\n", counter);
				fflush(fp);
			}
			if(ferror(fp))
				err_sys("Parent: fputc error");
 
			TELL_CHILD(pid);
		}
	}
 
	fclose(fp);
	close(fd);
	return 0;
}
Categories: 书山有路 Tags: , , , ,

APUE2e Exercise 10.6 – Solution B

February 16th, 2012 No comments

Using Standard I/O Library to read and write the file.

?Download exercise10-6b.c
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/**   
 * apue-chap10: exercise10-6b.c
 *
 * Description: Standard I/O Library
 *
 * Created On: Feb 16, 2012 
 *
 * @author: Huang Zhu
 *
 * @email: zhuhuang.zp@gmail.com
 */
 
 
#include <apueerr.h>
#include <signal.h>
#include <stdio.h>
#include <fcntl.h>
 
static volatile sig_atomic_t sigflag;
static sigset_t newmask, oldmask, zeromask;
 
static void sig_usr(int signo)
{
	sigflag = 1;
}
 
void TELL_WAIT(void)
{
	if(signal(SIGUSR1, sig_usr) == SIG_ERR)
		perror("signal(SIGUSR1) error");
	if(signal(SIGUSR2, sig_usr) == SIG_ERR)
		perror("signal(SIGUSR2) error");
	sigemptyset(&zeromask);
	sigemptyset(&newmask);
	sigaddset(&newmask, SIGUSR1);
	sigaddset(&newmask, SIGUSR2);
 
	//block SIGUSR1 and SIGUSR2, and save current signal mask
	if(sigprocmask(SIG_BLOCK, &newmask, &oldmask) < 0)
		perror("SIG_BLOCK error");
}
 
void TELL_PARENT(pid_t pid)
{
	kill(pid, SIGUSR2);
}
 
void TELL_CHILD(pid_t pid)
{
	kill(pid, SIGUSR1);
}
 
void WAIT_PARENT(void)
{
	while(sigflag == 0)
		sigsuspend(&zeromask);  //set mask and sleep and wait
	sigflag = 0;
 
	if(sigprocmask(SIG_SETMASK, &oldmask,  NULL) < 0)
		perror("SIG_SETMASK error");
}
 
void WAIT_CHILD(void)
{
	while(sigflag == 0)
		sigsuspend(&zeromask);  //set mask and sleep and wait
	sigflag = 0;
 
	if(sigprocmask(SIG_SETMASK, &oldmask,  NULL) < 0)
		perror("SIG_SETMASK error");
}
 
int main(void)
{
	int fd, pid, ppid, counter, round = 5;
	FILE* fp;
	char *filename = "counter.file";
	int i, j;
 
	if((fd = open(filename, O_RDWR | O_CREAT | O_TRUNC | O_SYNC, S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH)) < 0)
		err_sys("open error");
 
	if((fp = fdopen(fd, "r+")) == NULL )
		err_sys("fdopen error");
 
	if(fputc(0, fp) != EOF){
		printf("Writing initial value of the counter: 0\n");
		fflush(fp); //if fflush is not used, the change of counter cannot be seen instantly by other readers.
	}
 
	if(ferror(fp))
		err_sys("fputc error");
 
	if((pid = fork()) < 0){
		err_sys("fork error");
	}else if(pid == 0){ //child
		ppid = getppid();
 
		for(i = 0;  i < round; i++){
			printf("\nChild: round %d\n", i+1);
 
			TELL_WAIT();
 
			counter = -1;
 
			rewind(fp);
			counter = fgetc(fp);
			printf("Child: read counter from the file: %d\n", counter);
 
			counter++;
			printf("Child: increase counter to: %d\n", counter);
 
			rewind(fp);
			if(fputc(counter, fp) != EOF){
				printf("Child: Write counter to the file: %d\n", counter);
				fflush(fp);
			}
			if(ferror(fp))
				err_sys("Child: fputc error");
 
			TELL_PARENT(ppid);
 
			WAIT_PARENT();
		}
 
		counter = -1;
		rewind(fp);
		counter = fgetc(fp);
		printf("\nChild: read counter from the file: %d\n", counter);
 
		exit(0);
	}else{ //parent
		for(j = 0; j < round; j++){
			TELL_WAIT(); //set up signal handler
 
			WAIT_CHILD();
			printf("\nParent: round %d\n", j+1);
			counter = -1;
 
			rewind(fp);
			counter = fgetc(fp);
			printf("Parent: read counter from the file: %d\n", counter);
 
			counter++;
			printf("Parent: increase counter to: %d\n", counter);
 
			rewind(fp);
			if(fputc(counter, fp) != EOF){
				printf("Parent: Write counter to the file: %d\n", counter);
				fflush(fp);
			}
			if(ferror(fp))
				err_sys("Parent: fputc error");
 
			TELL_CHILD(pid);
		}
	}
 
	fclose(fp);
	close(fd);
	return 0;
}
Categories: 书山有路 Tags: , , ,

APUE2e Exercise 10.6 – Solution A

February 16th, 2012 No comments

Using File I/O to read and write the file.

?Download exercise10-6a.c
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/**   
 * apue-chap10: exercise10-6a.c
 *
 * Description: FILE I/O
 *
 * Created On: Feb 15, 2012 
 *
 * @author: Huang Zhu
 *
 * @email: zhuhuang.zp@gmail.com
 */
 
#include <apueerr.h>
#include <signal.h>
#include <stdio.h>
#include <fcntl.h>
 
static volatile sig_atomic_t sigflag;
static sigset_t newmask, oldmask, zeromask;
 
static void sig_usr(int signo)
{
	sigflag = 1;
}
 
void TELL_WAIT(void)
{
	if(signal(SIGUSR1, sig_usr) == SIG_ERR)
		perror("signal(SIGUSR1) error");
	if(signal(SIGUSR2, sig_usr) == SIG_ERR)
		perror("signal(SIGUSR2) error");
	sigemptyset(&zeromask);
	sigemptyset(&newmask);
	sigaddset(&newmask, SIGUSR1);
	sigaddset(&newmask, SIGUSR2);
 
	//block SIGUSR1 and SIGUSR2, and save current signal mask
	if(sigprocmask(SIG_BLOCK, &newmask, &oldmask) < 0)
		perror("SIG_BLOCK error");
}
 
void TELL_PARENT(pid_t pid)
{
	kill(pid, SIGUSR2);
}
 
void TELL_CHILD(pid_t pid)
{
	kill(pid, SIGUSR1);
}
 
void WAIT_PARENT(void)
{
	while(sigflag == 0)
		sigsuspend(&zeromask);  //set mask and sleep and wait
	sigflag = 0;
 
	if(sigprocmask(SIG_SETMASK, &oldmask,  NULL) < 0)
		perror("SIG_SETMASK error");
}
 
void WAIT_CHILD(void)
{
	while(sigflag == 0)
		sigsuspend(&zeromask);  //set mask and sleep and wait
	sigflag = 0;
 
	if(sigprocmask(SIG_SETMASK, &oldmask,  NULL) < 0)
		perror("SIG_SETMASK error");
}
 
int main(void)
{
	int fd, pid, ppid, counter, round = 5;
	char *filename = "counter.file";
	char *rbuf, *wbuf;
	int i, j;
 
	rbuf = (char *)malloc(sizeof(int));
	wbuf = (char *)malloc(sizeof(int));
 
	if((fd = open(filename, O_RDWR | O_CREAT | O_TRUNC, S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH)) < 0)
		err_sys("open error");
 
	if(sprintf(wbuf, "%d", 0) < 0)
		err_sys("sprintf error");
 
	if(write(fd, wbuf, sizeof(int)) > 0 ){
		printf("Writing initial value of the counter: %s\n", wbuf);
		fsync(fd);
	}
 
	if((pid = fork()) < 0){
		err_sys("fork error");
	}else if(pid == 0){ //child
		ppid = getppid();
 
		for(i = 0;  i < round; i++){
			printf("\nChild: round %d\n", i+1);
 
			TELL_WAIT(); //set up signal handler
 
			counter = -1;
 
			if(lseek(fd, 0, SEEK_SET) != 0)
				err_sys("Child: lseek error");
			if(read(fd, rbuf, sizeof(int)) < 0)
				err_sys("Child: read error");
			if(sscanf(rbuf, "%d", &counter) == EOF)
				err_sys("Child: sscanf error");
			printf("Child: read counter from the file: %d\n", counter);
 
			counter++;
			printf("Child: increase counter to: %d\n", counter);
 
			if(lseek(fd, 0, SEEK_SET) != 0)
				err_sys("Child: lseek error");
			if(sprintf(wbuf, "%d", counter) < 0)
				err_sys("Child: sprintf error");
 
			if(write(fd, wbuf, sizeof(int)) > 0 ){
				printf("Child: Write counter to the file: %s\n", wbuf);
				fsync(fd);
			}
 
			TELL_PARENT(ppid);
 
			WAIT_PARENT();
		}
 
		counter = -1;
		if(lseek(fd, 0, SEEK_SET) != 0)
			err_sys("Child: lseek error");
		if(read(fd, rbuf, sizeof(int)) < 0)
			err_sys("Child: read error");
		if(sscanf(rbuf, "%d", &counter) == EOF)
			err_sys("Child: sscanf error");
		printf("\nChild: read counter from the file: %d\n", counter);
 
		close(fd);
		exit(0);
	}else{ //parent
		for(j = 0; j < round; j++){
			TELL_WAIT(); //set up signal handler
 
			WAIT_CHILD();
			printf("\nParent: round %d\n", j+1);
			counter = -1;
 
			if(lseek(fd, 0, SEEK_SET) != 0)
				err_sys("Parent: lseek error");
			if(read(fd, rbuf, sizeof(int)) < 0)
				err_sys("Parent: read error");
			if(sscanf(rbuf, "%d", &counter) == EOF)
				err_sys("Parent: sscanf error");
			printf("Parent: read counter from the file: %d\n", counter);
 
			counter++;
			printf("Parent: increase counter to: %d\n", counter);
 
			if(lseek(fd, 0, SEEK_SET) != 0)
				err_sys("Parent: lseek error");
			if(sprintf(wbuf, "%d", counter) < 0)
				err_sys("Parent: sprintf error");
 
			if(write(fd, wbuf, sizeof(int)) > 0 ){
				printf("Parent: Write counter to the file: %s\n", wbuf);
				fsync(fd);
			}
 
			TELL_CHILD(pid);
		}
	}
 
	close(fd);
	return 0;
}
Categories: 书山有路 Tags: , , ,