Member Avatar for Barefootsanders

Hey everyone,

I'm attempting to write a program that will pipe and fork to have a parent and child process. Then the parent writes numbers to the pipe and the child either multiplies or divides the two numbers. For some reason my file I/O isn't working. It's supposed to keep a log of actions etc. Below is the bulk of my code. Any suggestions to get it working would be very much appreciated. What it does now is write the child log, but not the parent or output log.

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <time.h>
#include <string.h>
#include <signal.h>

void signalHandler(int);
void getTime(char*);
void addDot(char*);
int cFlag = 0, alarmFlag = 0, childFinishedFlag = 0;

int main() {
	char outputFileName[100], parentFileName[100], childFileName[100];
	int parentPID = getpid(), childPID, fd[2];
	char timeString[30];
	const int MAXLINE = 4096;
	char line[MAXLINE];

	//Set up signals
	signal(SIGINT, signalHandler);
	signal(SIGCHLD, signalHandler);
	signal(SIGALRM, signalHandler);
	
	//Populate timeString array with current time
	getTime(timeString);
	
	//Prompt user for output filename
	scanf("%100s", outputFileName);
	addDot(outputFileName);
	if(cFlag == 1) {
		strcpy(outputFileName, "Output.");
	}
	
	//Populate other filename strings
	strcpy(parentFileName, "ParentStatus.");
	strcat(parentFileName, timeString);
	strcpy(childFileName, "ChildStatus.");
	strcat(childFileName, timeString);
	
	//File pointers
	FILE *outputFile;
	FILE *parentLog;
	FILE *childLog;

	//Open outputfile
	if((outputFile = fopen(strcat(outputFileName,timeString), "w")) == NULL) {
		printf("Error opening output file.\n");
		return 1;
	}
	else {
		//Write output file info here
		fprintf(outputFile, "Opened: %s\n", timeString);
	}
	
	
	//Create pipe
	if (pipe(fd) < 0) {
		printf("Pipe Error, program closing");
		return 1;
	}
		
	//Fork returns the PID of the child process
	if ((childPID = fork()) < 0)	{
		printf("Fork Error");
		return 1;
	}	
	//Parent process
	else if (childPID > 0) {
		//Open parent log file
		if((parentLog = fopen(parentFileName,"w")) == NULL) {
			printf("Error opening output file.\n");
			return 1;
		}
		else {
			fprintf(parentLog, "Opened: %s\n", timeString);
			
			//Set standard output
			dup2(fd[1], STDOUT_FILENO);
			
			//Close the reading end of the pipe
			close(fd[0]);
			
			
			//Write output file info here
			fprintf(parentLog, "Parent Log\nPID: %i\n", parentPID);
			
			//Seed for random number
			srand((int)time(NULL));
			int num;
			
			//Wait for child to finish
			while(childFinishedFlag == 0) {
				//Generate new number
				num = (int)(5.0 * rand() / (RAND_MAX + 1.0));
				//Write to pipe
				write(STDOUT_FILENO, &num, 1);
			}
						
			//When child is finished, close parent log and output file
			getTime(timeString);
			fprintf(parentLog, "Parent finished at: %s", timeString);

		}
	}
	//Child process
	else {
		
		//Open child log file
		if((childLog = fopen(childFileName,"w")) == NULL) {
			printf("Error opening output file.\n");
			return 1;
		}	
		else {
			fprintf(childLog, "Opened: %s\n", timeString);
			
			//Set standard input
			dup2(fd[0], STDIN_FILENO);
			
			//Seed rand and set alarm
			srand((int)time(NULL));
			int randTime = 1 + (int)(10.0 * rand() / (RAND_MAX + 1.0));
			alarm(randTime);
			
			int n1, n2, num1, num2;
			while(alarmFlag == 0) {
				//Get 2 random numbers
				n1 = read(STDIN_FILENO, &num1, 1);
				n2 = read(STDIN_FILENO, &num2, 1);
				//DEBUG: printf("Number: %i, %i\n",num1, num2);
				
				//If the first number is greater than 2, multiply, otherwise divide
				if(num1 > 2) {
					int result = num1 * num2;
					fprintf(childLog, "%i * %i = %i\n", num1, num2, result);	
				}
				else {
					//int result = num1 / num2;
					//fprintf(childLog, "%i / %i = %i\n", num1, num2, result);
				}
				
			}
			
			//When alarm goes off close child log
			getTime(timeString);
			fprintf(childLog, "Child finished at: %s", timeString);
			fclose(childLog);
			
		}
	}
	
	
	fprintf(outputFile, "Output finished at: %s", timeString);	
	fclose(parentLog);
	fclose(outputFile);
	
	return 0;
}

/*
 * signalHandler(int) - Handles the signals generated by the program
 */ 
void signalHandler(int signo) {
	//Ctrl-C Handler
	if(signo == SIGINT) {
		cFlag = 1;
	}
	//Signal when child is finished
	if(signo == SIGCHLD) {
		childFinishedFlag = 1;
	}
	//Signal when alarm goes off in child program
	if(signo == SIGALRM) {
		alarmFlag = 1;
	}
}

/*
 * getTime(char*) - Gets the current time and populates the string
 * passed as a parameter.
 */
void getTime(char *timeString) {
	time_t clock;
	struct tm *theTime;
	time(&clock);
	
	theTime = localtime(&clock);
	strftime(timeString,29,"%T",theTime);
}

/*
 * addDot(char*) - A support function. Simply adds a dot to the filename.
 */
void addDot(char *string) {
	strcat(string, ".");
}
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  • 12 Hours Discussion Span
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Member Avatar for Barefootsanders

I'm pretty sure its getting stuck in one of the while loops for some reason but I cant tell why. Any help?

Member Avatar for WaltP

121 posts and you still can't make a proper title? And you should know by now most of us won't help without posting code, nor will we download it.

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