Thread: Need some help with pipes please.

I've been beating myself over the head for days now on this project, and I can't seem to find any kind of possible resolution.

To put it simply, the program is supposed to fork a process for each regular file in a directory specified at the command line (which each will enter a loop waiting for data from the parent), and use pipes to communicate with the parent.

The parent then askes the user for a character to search for, and pipes this to each one of the children. The children then search the files they have open and pipe a count back to the parent, who then totals these counts up and prints the sum.

For some reason, I cannot get the parent process to execute at all. I tried the program on a test directory with two files, and it seems that I get 2 processes forked, but then the parent never executes afterwards, leaving my program in kind of a deadlock.

Any help would be apperciated!

Code:

 #include <stdio.h>
#include <sys/types.h>
#include <dirent.h>
#include <unistd.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/uio.h>

char searchChar;
int searchCharNum = 0, checkedFileCount=0, numFiles = 0;
/***********************************************************/

void die(const char*errmsg);
void* search(void* fileName, pid_t writeHandle, pid_t readHandle);


int main(int argc, char *argv[])
        {
        if (argc != 2)
          die("Only accepts one arguement, a directoryname\n");

        DIR *dirp = opendir(argv[1]);
        if(!dirp)
          die("The directory name you provided is an invalid directory.\n");
	
	if(chdir(argv[1]) !=0)
		die("Error changing directory");
	pid_t pid;
	char Buffer[1];
	int c2p[256][2], p2c[1];     /* child to parent pipe */
        struct dirent *dp;
        pipe(p2c);

	while((dp = readdir(dirp)) != NULL)
                {
                struct stat sb;
		if(stat(dp->d_name, &sb) != -1)
		  {
		  if(S_ISREG(sb.st_mode))
		    {
		    numFiles = numFiles + 1;
		    if((pid = fork()) == 0)
		    	{
		    	pipe(c2p[numFiles]);
			close(c2p[numFiles][0]); // close write end of the pipe
			close(p2c[1]); // close write end
		    	search(dp->d_name, c2p[numFiles][1], p2c[0]);
			_exit(0);
		        }
		    }
		  }
		}
	while(1)
		{
		close(p2c[0]); 
		int i = 0;
		while(i < numFiles)
			close(c2p[i][1]);
		int total = 0;
		printf("Enter a character to search for(Ctrl+D and [enter] to stop): ");
		searchChar = getchar(); //get the first char.
		while(getchar() != '\n'); /* clear out anything else */
		searchCharNum++;          /* that may be in stdin    */
		
		if (searchChar == (char)EOF)
			{
			printf("Goodbye\n");
			break;
			}
		write(p2c[1], Buffer, 1);
		while(checkedFileCount != numFiles); 
			// do nothing
		int j = 0;
		printf("%d\n",numFiles);
		while(j < numFiles)
			{
			read(c2p[j][0], Buffer, 1);
			printf("%c\n",Buffer[0]);
			total += (int)Buffer[0];
			i++;
			} 
		printf("\nThere where %d occurances of %c found in %d files listed in the directory %s\n", total, searchChar, numFiles, argv[1]);
		searchCharNum = 0;
		}
		
        (void)closedir(dirp);
        
        return 0;
        }

void die(const char*errmsg)
    {
    printf("%s\n",errmsg);
    exit(1);
    }

void* search(void* fileName, pid_t writeHandle, pid_t readHandle)
	{
	char Buffer[1]; // we only need one character
	while(1)
		{
		char x;
		while(searchCharNum == 0)
			sleep(1); // take a nap
		
		read(readHandle, Buffer, 1);
		int count = 0;
		FILE *fd;
		if((fd = fopen(fileName,"r")) !=NULL)
			{
			while((x = fgetc(fd)) != EOF)
				if (x == Buffer[0])
					count++;
			}
		 else
			die("error opening file");
		Buffer[0] = count;
		write(writeHandle, Buffer, 1); 	 
		}
	}

Here's a couple of things:

What terminates this loop:

Code:

    while (i < numFiles)
    {
      close(c2p[i][1]);
    }

>>int p2c[1]
How many elements in that array? Don't you need two?

>>printf("Enter ...
Use fflush(stdout); after this line to force the text to the screen.

>>searchChar == (char) EOF)
Don't use a cast here. Make searchChar an int. See:
http://faq.cprogramming.com/cgi-bin/...&id=1043284351

>>write(p2c[1], Buffer, 1);
Which child are you intending to write to? I'm not sure that the data will go to all children (have to look that one up).