Using strcmp() on STDIN_FILENO

Question

        char buf[BUF_SIZE + 1];
        printf("[Enter Command]: \n");
        num_read = read(STDIN_FILENO, buf, BUF_SIZE);
        if (num_read == 5) {
            exit(0);
        }

I want to check if the user input is the string "exit" and exit the program if it is. The snippet above works but it will exit on all 4 letter strings. I only want it to exit on the string "exit".

I don't understand why the code below doesn't work:

if (strcmp("exit", buf) == 0) {
    exit(0);
}

What is `exit_call`? You haven't defined it anywhere. You can expect help only if you show all relevant parts of code. — Binarus, Apr 03 '18 at 08:09
You simply need to add the null byte after `read` call: `if (num_read > 0) buf[num_read] = '\0';`. — P.P, Apr 03 '18 at 08:17
just add '\0' at the end replacing '\n' buf[strcspn(buf, "\n")] = '\0' — Nick S, Apr 03 '18 at 08:23
@static To understand what happens just use printf("[%s]\n", buf); after read and you will see that string contains line feed at the end. As you know all string should contains null terminator char at the end. So all magic is to replace '\n' to '\0'; — Nick S, Apr 03 '18 at 08:33

score 0 · Answer 1 · answered Apr 03 '18 at 08:11

0

The strcmp() isn't working since read() is not 0-terminating the input, it's not doing string input.

Use e.g. fgets() to read a full line, then check if it starts with exit (remember that it will contain the linefeed).

answered Apr 03 '18 at 08:11

unwind

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https://pastebin.com/rHQmRUtg – static Apr 03 '18 at 08:17
I just receive a `Segmentation fault (core dumped)` with this. – static Apr 03 '18 at 08:18

Using strcmp() on STDIN_FILENO

1 Answers1