How could I write a C program that takes an integer from command line?

Question

I want to write a C program that takes positive integer n from standard input, and outputs n+1. It is supposed to work like this

./myprog 3   
--> returns 4

./myprog -2
--> crashes

I tried using scanf. But it does not take standard input from the command line. Any code template to help me out? Thanks.

Earlier, I also tried

#include <stdio.h>
int main( ) {

   int c;

   printf( "Enter a value :");
   c = getchar( );

   printf( "\nYou entered: ");
   putchar( c );

   return 0;
}

It does not give a command-line solution neither.

Look at argv and argc. You get arguments from the command line. Minimal solution: int main(int argc, char *argv[]) { int cmdval = atoi(argv[1]); if (cmdval < 0) return 1; printf("%d\n",cmdval); return 0; } — LambdaBeta
– LambdaBeta, Commented Oct 5, 2016 at 19:20
Thanks. Please help and do not downvote or I 'll be kicked out from the forum. — wad
– wad, Commented Oct 5, 2016 at 19:22
I didn't downvote, but I can guess why someone did. People don't like wasting their time. On the surface your question looks like a copy-pasted homework assignment. Only your description of your research into scanf identified that your problem was with terminology (input vs arguments). Next time try posting a short program that doesn't work, but is close, and you'll probably have more success. Good Luck. — LambdaBeta
– LambdaBeta, Commented Oct 5, 2016 at 19:24
It works, but is terrible. Easy to break, no checks, no formatting, abuses return value, etc. But good enough for an example. :) — LambdaBeta
– LambdaBeta, Commented Oct 5, 2016 at 19:36

lolololol ol · Accepted Answer · 2016-10-05 21:00:59Z

1

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

int main(int argc, char * argv[])
{
     int n = atoi(argv[1]); // n from command line
     n = n + 1; // return n + 1
     printf("%d", n);

     return 0;
}

answered Oct 5, 2016 at 21:00

lolololol ol

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