How to properly compare command-line arguments?

问题

I am trying to write a C code which takes arguments in main; thus when I write some strings in cmd, the program doing somethings inside it. But I am doing something wrong and I can't find it.

This is the code:

#include <stdio.h>
#include <stdlib.h>

int main(int argc, char * argv[]){   //File name is main.c
    if(argc != 3)
        printf("Wrong!!!!!!!!!");
    else
        if (argv[1] == "-s")
            girls();  //Prints "Girls"
        else if(argv[1] == "-k")
            boys();   //Prints "Boys"
        else
            printf("OMG!!");
}

In the cmd;

gcc -o gender main.c

gender -s pilkington

I enter that commands. Bu the output is always

"OMG!!"

Which part is wrong?

回答1:

In your code, argv[1] == "-s" is the erroneous part. comparison of strings cannot be done with == operator.

To compare strings, you need to use strcmp().

Your code should look like

if ( ! strcmp(argv[1], "-s")) { //code here }

if you want to check if argv[1] contains "-s" or not.

回答2:

Compare the two strings using the strcmp(s1,s2) function.

            if (strcmp(argv[1],"-s")==0)
                    girls();  //Prints "Girls"
            else if(strcmp(argv[1],"-k")==0)
                    boys();   //Prints "Boys"
            else
                    printf("OMG!!");

回答3:

if you check the argv[1] == "-s" the condition will not be true. since it is a string you can use the strcmp function.

     if(( strcmp(argv[1],"-s")) == 0)
     girls();
     else if ((strcmp(argv[1],"-k")) == 0)
     boys();

Try this..

回答4:

You have to compare the string using the strcmp function. You cannot simply check the string in equality operator.

  int strcmp(const char *s1, const char *s2);

Try this in your code.

if ((strcmp(argv[1],"-s")==0)

来源：https://stackoverflow.com/questions/27525617/how-to-properly-compare-command-line-arguments

标签

string

command-line-arguments

string-comparison

strcmp