Command line parameter for C program

Applications Programming
1

I am writing a C program that part of the idea is to using a command line parameter to control not to run certain part of the sub program.

I am totally new to C, I do not have any idea how to pass a command line arguments from a C program.

Can anyone help ?!

Thanks

2

You can try to declare main with arguments;

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

This program was used in an application, where a PC was controlling critical tasks. Lets call it PC_critical. Unfortunately, PC_critical occasionally stalled and had to be manually reset.

Thus, a second PC (PC_monitor) was used. PC_critical was to send a message to PC_monitor every five minutes to assure that it was "alive". If no message was received, PC_monitor forced a hard reset of PC_critical by applying a momentary relay closure across the manual reset switch on PC_critical. The operation of the relay was caused by outputting the pattern 0x0a on the Data Port.

You can try this as an example.


#include <stdio.h>
#include <conio.h>
#include <dos.h>
#include <process.h>

int main(int argc, char *argv[])
{
   unsigned int t_delay, Data;
   int tenths_sec;

   clrscr();

   if(argc != 3)
   {
      printf("Incorrect number of args\n");
      exit(-1);
   }
   if(sscanf(argv[1],"%d", &tenths_sec)!=1)
   {
      printf("Time scanf failed.\n");
      exit(-2);
   }
   if (sscanf(argv[2],"%x", &Data) != 1)
   {
      printf("Parallel port scanf failed.\n");
      exit(-3);
   }
   t_delay = tenths_sec * 100;
   outportb(Data, 0x0a); /* operate the relay */
   delay(t_delay);
   outportb(Data, 0x00); /* release it */
   exit(0);
}
3

Thanks Killerserv !!

4

Hi,

I have some additional infor for you. There is one more arg to main. It is the char *env[]. which is very similar to char *argv[]. This arg contains all the system variables set up in the environment. Also there is a workaround for the same. you also have a getenv function which can help you get these arguments.

Happy programming buddy

penguin