Question

This is a small C program concerning pipes and processes, The Father process will create 2 child processes, the first will read the numbers out of a chain, the second will read the letters. I started by asking for the WORD, I didnt add protection this is just a test, so lets say about 20 letters, then the father process will write the numbers in the first pipe, and the letters in the second pipe, then he will create a child using fork(), if he’s the child , he will read the numbers from the first pipe, if he’s the father, then he will create another child, to read the letters.

# include <stdio.h>
# include <unistd.h>
# include <string.h>
# include <fcntl.h>

main()
{
    printf("I am the father, I will create 2 sons, the first will read the numbers , the second will read the letters\n");
    char * word;
    printf("please type the word: \n");
    scanf("%s",word);
    printf("Now 2 pipes will be created\n");
    int fd1[2];
    int fd2[2];
    pipe(fd1); pipe(fd2);
    printf("Now the father will write numbers in the first pipe, and letters in the second\n");
    int i;
    char numbers[20]; int j=0;
    char caracters[20]; int k=0;
    for (i=0;i<20;i++)
    {
        if(word[i]>='0' && word[i]<='9') //if number
        {
            close(fd1[0]); //closing reading
            write(fd1[1],word[i],2);

        }
        else
        {
            close(fd2[0]);  
            write(fd2[1],word[i],2);
        }

    }
    printf("The father has wrote in the 2 pipes, now its time for the sons\n");
    int f=fork();
    if(f==0) //first son
    {
        for(i=0;i<20;i++) {         
            close(fd1[1]); //closing writing
            read(fd1[0],numbers[j],strlen(numbers[j])+1);
            j++;

        }
        printf("first son read everything, he got %d Numbers\n", j);
    }
    else
    {
        f=fork();
        if(f==0)
        {
            for(i=0;i<20;i++) {         
            close(fd2[1]); //closing writing
            read(fd2[0],caracters[k],strlen(caracters[k])+1);
            k++;

        }   
        printf("second son read everything, he got %d caracters\n", j);
    }
}

after compiling :

In function 'main':
Line 25: warning: passing argument 2 of 'write' makes pointer from integer without a cast
Line 31: warning: passing argument 2 of 'write' makes pointer from integer without a cast
Line 41: warning: passing argument 1 of 'strlen' makes pointer from integer without a cast
Line 41: warning: passing argument 2 of 'read' makes pointer from integer without a cast
Line 54: warning: passing argument 1 of 'strlen' makes pointer from integer without a cast
Line 54: warning: passing argument 2 of 'read' makes pointer from integer without a cast
Line 60: error: expected declaration or statement at end of input

Answer 1

The prototype of write and read are

ssize_t write(int fd, const void *buf, size_t count);

ssize_t read(int fd, void *buf, size_t count);

Argument 2 to write/read should be a pointer. But what you are sending is a character (which is an integer in fact) word[i] and numbers[i]

Same problem even with your strlen

Also, declare word as an array instead of just a pointer. Else you would be writing to wherever random location the pointer is pointing to. Or if you wanna keep it as a pointer, malloc some memory for it.

After all this, just pass word, numbers instead of numbers[j] or words[i] to your functions which are complaining

EDIT: Also your last for statement for(i=0;i<20;i++) lacks a closing brace and hence the Line 60: error: expected declaration or statement at end of input error