Handling scanf(reading values) in a program at once while executing the program

[chansra agnuru]

Hi,

I need some information regarding how to handle scanf values while executing the program itself.
For example:

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

char str[20];
printf("first argument: %s",__argv[1]);
printf("Second argument: %s",__argv[2]);

printf("Enter your name:");
gets(str);

)

suppose the program exe name is BYTE then in order to execute from command prompt we need to give:
BYTE 1arg 2arg ->ENTER
it asks to enter your name

My question is how can i give name at executing itself
like
BYTE 1arg 2arg << anna hazare

will it work???

[Peter Lesslie]

You could rewrite the program to check if argc had 3 arguments. If it did then use that as the name, if argc == 2 then ask for the name.

[chansra agnuru]

ya the program required two arguments like i mentioned, but how can i get rid of entering name after execution??..is their any facility to read vlues for scanf at execution time itself??

[Peter Lesslie]

This is what I mean:

#include <stdio.h>

int main(int argc, char* argv[])
{
if ( argc == 3 ) {
printf ("first argument: %s",__argv[1]);
printf ("second argument: %s",__argv[2]);
printf ("Name: %s",__argv[3]);
}
else {
char str[20];
printf("first argument: %s",__argv[1]);
printf("Second argument: %s",__argv[2]);

printf("Enter your name:");
gets(str);
}

return 0;

}

[chansra agnuru]

I agree with you in the first case (__argc==3) i am asking about else part which you have sent.From the command prompt we can execute a program by giving required arguments right.so how can i give values for a program during execution time(like arguments)inste ad giving at run time and press ENTER for scanf??.I hope this will clear :-)

[Peter Lesslie]

On a *nix system you could use something like

echo "What ever you want to pass" | a.out

where a.out is your program. Is that what you mean? (I'm not sure how/(if it exists) the pipe works on Windows.

[chansra agnuru]

Yes by using the above command we can pass value to only one scanf/gets. If the program is having multiple scanfs then how can we pass?For better understanding am sending the code..

int main( int argc, char* argv[])
{
char buf[20];
char bug[20];
printf("fisrt arg:%s\n",argv[1]);
printf("second arg:%s\n",argv[2]);

printf(" enter name1:");
gets(buf);

printf("Enter name2:");
gets(bug);

printf("\n First Scanf:\n");
puts(buf);
printf("second scanf: \n");
puts(bug);
printf("\n********* END*****");
return 0;
}

If I give: echo "Peter Lesslie" | ./a.out FIRST SECOND
The Output is: echo "Peter Lesslie great" | ./a.out FIRST SECOND
fisrt arg:FIRST
second arg:SECOND

enter name1:
Enter name2:
First Scanf:
Peter Lesslie great
second scanf:

But i want out put like:
First Scanf:
Peter
second scanf:
Lesslie great

Is this any seperator required in echo???

[Peter Lesslie]

#include <cstdio>

int main( int argc, char* argv[])
{
char buf[20];
char bug[20];
printf("fisrt arg:%s\n",argv[1]);
printf("second arg:%s\n",argv[2]);
 
printf(" enter name1:");
scanf("%s",buf);
 
printf("Enter name2:");
gets(bug);
 
printf("\n First Scanf:\n");
puts(buf);
printf("second scanf: \n");
puts(bug);
printf("\n********* END*****\n");
return 0;
}

This works for me. (gets is not delimited by spaces so it will take all the initial input while if you make the first one a scanf then it won't do that.

[chansra agnuru]

Hi,

I have tried
echo "peter\nLes slie great"| ./a.out FIRST SECOND

It worked.Thanks for the information you have given till now though i have squeezed you!!.. :-))