Program displays strange characters on the screen - c

Question

I'm developing a client-server program, and this is my server_2 file, who will comunicate with the main server.
The program displays on the screen these lines when is running. I think that those lines after the mkfifo are causing this.
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Structures
typedef struct request req;
struct request
{
char str[256];
int client_pid;
int login; // In case of client, to identify if is logged
int whois; // To identify who is the client and the server
};
typedef struct answer ans;
struct answer
{
char str[256];
int server_pid;
int type;
int login;
int num_users;
};
Main:
#include "header.h"
int main(int argc, char *argv[])
{
int fifo_1, fifo_2;
struct request req;
struct answer ans;
if(argc == 2) // Check if the command was well prompted
{
if(strcasecmp(argv[1], "show") == 0 || strcasecmp(argv[1], "close") == 0)
{
if(fifo_2 = open("FIFO_SERV", O_WRONLY) == -1)
{
perror("[SERVER_2] Error: on the FIFO_SERVER opening!\n");
sleep(2);
exit(EXIT_FAILURE);
}
if(mkfifo("FIFO_SERV_2", 0777) == -1)
{
perror("[SERVER_2] Error: on the FIFO_SERVER_2 creation!\n");
sleep(2);
exit(EXIT_FAILURE);
}
strcpy(req.str, argv[1]); // Copy the argumento to the structure
write(fifo_2, &req, sizeof(req)); // Write a request to the server
strcpy(req.str,""); // Clean the string
fifo_1 = open("FIFO_SERV_2", O_RDONLY);
read(fifo_1, &ans, sizeof(ans)); //Read an answ
}
//close(fifo_1);
unlink("FIFO_SERVER_2");
sleep(2);
exit(EXIT_SUCCESS);
}

Answer 1

The precedence rules of operators = and == make the line
if(fifo_2 = open("FIFO_SERV", O_WRONLY) == -1)
equivalent to
if(fifo_2 = (open("FIFO_SERV", O_WRONLY) == -1))
which essentially assigns 0 to fifo_2 if open succeeds and 1 if open fails. The values 0 and 1 also happens to be the respective values of the standard input and output file descriptor in POSIX standard library implementations (see File descriptor on wikipedia), so later when you execute
write(fifo_2, &req, sizeof(req)); // Write a request to the server
you are either trying to write to standard input (undefined behavior), or to standard output depending on whether the file could be opened rather than to the server. To fix this, you can replace the open expression with:
if((fifo_2 = open("FIFO_SERV", O_WRONLY)) == -1)
Then, you may have to figure out why you can't open the file (since you are presumably writing to standard output, which means open failed).