./writer & # Run script1 in the background
./reader # Run reader in the foreground
wait # wait for writer to finish

#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h> // For strlen
#include <fcntl.h>
#include <limits.h>
#include <sys/types.h>
#include <sys/stat.h>

int main(int argc, char* argv [])
{
        int readfd, writefd;
        // If you're going to read PIPE_BUF bytes, you might as well have
        // a buffer big enough to hold PIPE_BUF bytes.
        // Otherwise, if you ever read more than 100, it'll crash!
        char buffer [PIPE_BUF];

        if(argc != 2)
        {
                // Error messages belong on standard error.
                fprintf (stderr, "Invalid number of argument. Enter an integer\n");

                // Instead of chaining if/else 99 deep, 
                // quit the program early.
                return(1);
        }

        // Good idea!
        if (access ("pipe1", F_OK) == -1)   //if pipe1 cannot be accessed
       {
                int res = mkfifo ("pipe1", 0660);
                if (res != 0)
                {
                        Error messages belong on standard error.
                        fprintf (stderr, "ERROR: Pipe cannot be created\n");
                        // Instead of chaining if/else 99 deep, 
                        // quit the program early.
                        return(1);

                }
        }

        writefd = open ("pipe1", O_WRONLY);

        //argv[1] is already a pointer, no need to take its address.
        // Don't write PIPE_BUF bytes unless you actually have PIPE_BUF bytes!
        // The string is exactly strlen() bytes long.
        //write (writefd, &argv[1], PIPE_BUF);
        write(writefd, argv[1], strlen(argv[1]));

        close (writefd);

        return (0);
}

 #include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <fcntl.h>
#include <limits.h>
#include <sys/types.h>
#include <sys/stat.h>

int main ()
{
        int readfd, value;
        ssize_t bytes;
        // If you're going to read PIPE_BUF bytes, you might as well have
        // a buffer big enough to hold PIPE_BUF bytes.
        // Otherwise, if you ever read more than 100, it'll crash!
        char buffer [PIPE_BUF];

        //mkfifo ("pipe2", 0660);

        readfd = open ("pipe1", O_RDONLY);
        bytes=read (readfd, buffer, PIPE_BUF);

        fprintf(stderr, "Read %d bytes\n", (int)bytes);

        // Put a NULL terminator on the end so printf/strlen/etc won't crash.
        buffer[bytes]='\0';        

        // buffer is a character array, not an integer.
        // You can't do math on it until you convert it.
        printf ("Buffer has %s\n", buffer);

        if(sscanf(buffer, "%d", &value) != 1)
        {
                fprintf(stderr, "string '%s' is not a number\n", buffer);
                return(1);
        }

        printf("value is %d\n", value);

        // convert back into a string
        sprintf(buffer, "%d", value+10);

        printf("buffer is now %s\n", buffer);
        close(readfd);
        return 0;
}