CODEWITHSUNDEEP
c
JohnHoulderUK
JohnHoulderUK

Reputation: 679

C program not reading arguments correctly

I'm writing a program and I want to accept commandline arguments but when I pass any args, it acts as if start is always called. My code is below. Any help is appreciated.

//compile to iservices
// Ilkotech Services - C Core
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main(int argc, char *argv[]) {
    if (argc < 2) {
        printf("Usage: %s start|shutdown|reload\n",argv[0]);
    }
    else {
        if (strcmp(argv[1],"start") != 0) {
            services_start();
        }
        else if (strcmp(argv[1],"shutdown") != 0) {
            services_shutdown();
        }
        else if (strcmp(argv[1],"reload") != 0) {
            services_reload();
        }
        else {
            printf("%s is not a valid argument\n",argv[1]);
            printf("Usage: %s start|shutdown|reload\n",argv[0]);
            exit(1);
        }
    }
    return 0;
}
int services_start() {
    printf("Started.\n");
    return 0;
}
int services_shutdown() {
    printf("Shutting down!\n");
    return 0;
}
int services_reload() {
    printf("Reloading services configuration.\n");
    return 0;
}

Upvotes: 2

Views: 168

Answers (2)

John R. Strohm
John R. Strohm

Reputation: 7667

According to the online C++ reference, strcmp() returns zero if the strings are equal. That being the case, your code would be saying, essentially, if the first argument is NOT "start", run services_start().

Upvotes: 0

md5
md5

Reputation: 23699

strcmp returns 0 if the both strings are equals.

C11 (n1570), § 7.24.4.2 The strcmp function
The strcmp function returns an integer greater than, equal to, or less than zero, accordingly as the string pointed to by s1 is greater than, equal to, or less than the string pointed to by s2.

Some programmers used to call the following macro:

#include <string.h>
#define cmp_strings(a, b) (strcmp(a, b) == 0)

Upvotes: 7

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