Reading multiple messages using pipe in C?

Question

I understand that I can send a message from parent and receive it using read() from child using pipes, but what if I want to send multiple messages of different types (int, array..) to the child process? Is it possible to let the child process read them separately?

Answer 1

You can define various data types in enum and then append this enum in the beginning of your message.

typedef enum 
{
INT,
CHAR,
FLOAT,
LONG
//other data types
} data_type_t;

Say, your message is:

stackoverflow

and you need to indicate to the reciever to read it as a string, so you can append it like:

1stackoverflow //here 1 indicates CHAR

So, that one the child reads it, it can extract the 1st character to see that it has to be interpreted as string (CHAR). Use it as:

#define READ 0 /* Read end of pipe */
#define WRITE 1 /* Write end of pipe */
. . .

int fd[2];
char *message = "some random message";
char modified_message[40];

data_type_t type = CHAR; // Say for this message you define the data type as char

sprintf(modified_message, "%d%s", type,  message);
write(fd[WRITE], message, strlen(message)+1);
. . .

The receiving end will extract the 1st bit of the message and knowing the 1st bit you'll be able to interpret the type of the data contained.