CODEWITHSUNDEEP
cstructprocesspipe
Horatiu
Horatiu

Reputation: 61

Sending structure through pipe without losing data

I have this structure:

typedef struct {
    int pid;
    char arg[100];
    int nr;
} Str;

The code is something like this:

int main() {
    int c2p[2];
    pipe(c2p);
    int f = fork();

    if (f == 0) { // child
        Str s;
        s.pid = 1234;
        strcpy(s.arg, "abcdef");
        s.nr = 1;

        close(c2p[0]);
        write(c2p[1], &s, sizeof(Str*));
        close(c2p[1]);
        exit(0);
    }

    // parent
    wait(0);
    close(c2p[1]);
    Str s;
    read(c2p[0], &s, sizeof(Str*));
    printf("pid: %d nr: %d arg: %s", s.pid, s.nr, s.arg);
    close(c2p[0]);
    return 0;
}

The output is something like this:

pid: 1234 nr: 0 arg: abc$%^&

pid is always right, nr is always 0 and the fist few characters from arg are right followed by some random characters.

I want to create a structure in the child process and then send the structure to the parent process through pipe.

How can I send correctly this structure through pipe?

Upvotes: 1

Views: 3530

Answers (1)

R Sahu
R Sahu

Reputation: 206637

write(c2p[1], &s, sizeof(Str*));

is not right. That would write only the number of bytes the size of a pointer. It should be

write(c2p[1], &s, sizeof(Str)); // -- without the `*`.

Similarly, you need to use:

read(c2p[0], &s, sizeof(Str));  // -- without the `*`.

Upvotes: 3

Related Questions