使用来自命令行参数的输入将整数与非整数类型进行比较。 C

Question

I am looking to compare a users input to an integer once they enter some type whether that be a string or float etc. into the command line. If the input is not an integer, i want to produce an error message. I have tried using isdigit() and if(atoi(argv[i])>=0) but have had no luck. How do i go about doing this? Thanks in advance.

if( argc != 4 )
{
    printf("invalid.\n");
    error();
}
else if(atoi(argv[1]) >= 1 && atoi(argv[2]) >= 1 && atoi(argv[3]) >= 0){
    N = atoi(argv[1]);
    M = atoi(argv[2]);
    seed = atoi(argv[3]);

    mult(N,M,mat1,mat2,seed);
}
else
{
    printf("invalid argument.\n");
    error();

}

command line input:

$./filename 1 2 e

this still runs my program but i want it to exit when there's a non integer input.

Answer 1

Your program treats the third argument differently from the other two because you have atoi(argv[3]) >= 0 whereas the other two atoi() outputs are tested >= 1 . A return value of 0 can mean EITHER "I parsed that successfully and got an integer value of 0" OR "I couldn't parse that successfully" so the interpretation is conflated there if you wish to allow value 0 but don't perform additional checks.

Note also that ./filename 1x 2 3 is considered "valid" by your program. You may wish to take additional steps to ensure that the complete argument is a valid integer representation.

A better approach to both of these problems would involve switching to strtol or strtoul instead of atoi .