CODEWITHSUNDEEP
clinux
Keven Diuliy
Keven Diuliy

Reputation: 131

C Program to list files

I'm creating a very simple C program call open.c that will either:

1) List the files in the directory that will have the files text stored in an array

I have this code so far but it doesn't seem to work.

{ }

Upvotes: 0

Views: 217

Answers (3)

fvu
fvu

Reputation: 32953

The way you are trying to read command line arguments is wrong

Given

int main(int argc, const char * argv[])

the first argument to your program (eg "-ad") will get stored in argv[1]. You need to analyze that string to know what your program is expected to do.

Here's a basic intro to argc and argv. In real world programs there should be some protection as well: for example, the program should check whether it was actually called with a parameter by checking argc:

if (argc < 2) {
   printf("What do you want me to do?\n");
   return 3;
}

Alternatively - but try to get it working by handling the command line arguments manually at least once - you could delegate the entire command line handling to getopt.

Upvotes: 2

md5
md5

Reputation: 23699

You need to use argv to compare the command-line arguments with "-ah" and "-ad".

#include <string.h>

if (argc > 2)
{
  if (strcmp (argv[1], "-ah") == 0)
  {
    /* List hidden files */
  }
  else if (strcmp (argv[1], "-ad") == 0)
  {
    /* List files */
  }
  else
  {
    /* Unknown command-line argument */
  }
}
else
{
  /* No command-line arguments */
}

References:

C11 (n1570), § 5.1.2.2.1 Program startup

If they are declared, the parameters to the main function shall obey the following constraints:

— The value of argc shall be nonnegative.

— argv[argc] shall be a null pointer.

— If the value of argc is greater than zero, the array members argv[0] through argv[argc-1] inclusive shall contain pointers to strings, which are given implementation-defined values by the host environment prior to program startup. The intent is to supply to the program information determined prior to program startup from elsewhere in the hosted environment. If the host environment is not capable of supplying strings with letters in both uppercase and lowercase, the implementation shall ensure that the strings are received in lowercase.

— If the value of argc is greater than zero, the string pointed to by argv[0] represents the program name; argv[0][0] shall be the null character if the program name is not available from the host environment. If the value of argc is greater than one, the strings pointed to by argv[1] through argv[argc-1] represent the program parameters.

Upvotes: 3

Vaughn Cato
Vaughn Cato

Reputation: 64298

Instead of 

if (-ad)

you have to write something like

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

Same for if (-ah)

Upvotes: 2

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