C : String comparing - c

Question

bool done;
done = false;
while (!done) {
/* read the message */
bzero(msg, 100);
printf("[client]Type something: ");
fflush(stdout);
read(0, msg, 100);
if (strcmp(msg, "/done") == 0) {
done = true;
/* sending the message to the server */
if (write(sd, msg, 100) <= 0) {
perror("[client]Error sending the message to the server.\n");
return errno;
}
} else {
/* sending the message to the server */
if (write(sd, msg, 100) <= 0) {
perror("[client]Error sending the message to the server.\n");
return errno;
/* reading the answer given by the server*/
if (read(sd, msg, 100) < 0) {
perror("[client]read() error from server.\n");
return errno;
}
/* printing the received message */
printf("[client]The received message is: %s\n", msg);
}
}
Here's the code that i have problem with. So i want to send messages to the server until I send the message "/done", the code works, I send messages continuously but even when i type and send "/done" the process doesn't end.
I think there's a problem with the bzero function that "clears" the msg or maybe i don't understand it so good.
I also tried to wrote my own function to check if two strings are the same, but no effect also.
So how should i write the condition or "clear" the msg so i can send messages continuously and after i send "/done" the execution ends?
P.S. the msg is declared earlier in the code as char msg[100];

Answer 1

When you read from 0, you're reading from stdin. If that is a terminal that you are typing into (you don't say), you likely have it set up in normal (canonical) mode, so you'll read a line, which probably includes a newline (\n) character. So when you enter /done, the string you get in your msg buffer is "/done\n" which doesn't match "/done"...

Answer 2

read(2) is including the '\n' at the end of the string. When you use low-level read you get everything. When trying to debug strings, it can be helpful to put quotes in your print statement, like
printf("[client]The received message is: '%s'\n", msg);
as this immediately shows invisible whitespace.

Answer 3

TCP is not a message protocol. It does not glue bytes together into messages. If you want to use TCP to send and receive messages, you'll need to implement functions that send and receive messages.
I must strongly caution you not to fail into the trap of thinking that changing your code from happening not to work when you tried it to happening to work when you try it means that you've fixed it. Your code fails if read returns 1. You need to implement a sensible function to receive a message or your code will only be working by luck, and I can tell you from painful experience that one day your luck will run out.