Evaluating serial replies with if statement

Question

I am trying to read network statuses from a modem using an atmel MCU, and then debug/restart based on certain status replies. I do so with the following code (and this works):

scanf("%s", state);
printf_P(PSTR("%s\n%d\n"),state,tempstate);

    if (*state=='4'|| *state=='7' || *state == '9' || *state == '11' || *state == '12' || *state == '13' ||*state == '19' || *state == '30' || *state == '31')
    {
        count++;
        if(count == 5)
            {
                send_string("ATZ\r");
                _delay_ms(10000);
                count = 0;
            }
        else{}
    }

However, when trying to do something similar in a pin change interrupt (used for a door switch) I can read the modem reply 'OK', but when trying to confirm that reply with an if statement, the reply is not recognized. See below.

    send_string("AT\r\n");
    scanf("%s", reply);
    printf_P(PSTR("\n%s"),reply);

    if (*reply == 'OK')
    {
    printf_P(PSTR("\nWill text contact now."));
    send_string("AT*SMSM2M=\"15555555TESTING\"\r");
    scanf("%s", reply);
    }

I cannot manage to get my code to enter that if statement after the 'OK' is received. Any help is appreciated.

This `'OK'` is probably not what you think it is. `'` is for single chars(possibly multibyte). — Yunnosch, May 02 '18 at 18:27
`*reply == "OK"` this does also not what you think it does. For comparing strings use the appropriate string compare function, otherwise you compare pointers which are guaranteed to be different. — Yunnosch, May 02 '18 at 18:31

Yunnosch · Accepted Answer · 2018-05-02T18:48:08.327

1

See http://en.cppreference.com/w/c/string/byte/strcmp

For comparing the string "OK" (note the different quotes than in your code)
with what a char* reply points to, use

strcmp(reply, "OK")

Note that this returns 0 for identity.
Hence, an if similar to what you seem to try would be

if(!strcmp(reply, "OK"))

As mentioned by dbush in comment:
Note that you need to do this for the number comparisons as well, since you have strings containing numbers and not actual numbers.
Some of them (those comparing to a single character) misleadingly work, because you accidentally compare the first character of your reply string with a single-character char literal.

(As usual for "string" read "null-terminated sequence of chars.)

edited May 02 '18 at 18:48

answered May 02 '18 at 18:34

Yunnosch

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@masebee Note that you need to do this for the number comparisons as well since you have strings containing numbers and not actual numbers. – dbush May 02 '18 at 18:42
@dbush Good point. Thought it obvious but will add it to the answer, if you do not mind. – Yunnosch May 02 '18 at 18:44
1

@Yunnosch Go ahead. – dbush May 02 '18 at 18:44

Evaluating serial replies with if statement

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