About `argv` and opening a file with command line

I have this code:

#include <stdio.h>

int main ( int argc, char *argv[] )
{    
     FILE *file;
     int x;

     if ( argc != 2 )
           printf( "Use: %s file name", argv[0] );
     else {
            if ((file=fopen( argv[1], "r" ))== 0 ) 
            printf( “Couldn't open the file.\n" );
             else {
                          while (( x = fgetc( file ) ) != EOF)  printf( "%c", x );
                          fclose( file );
              }
      }
      return 0;
}

Now, having this code, how do I execute a file from terminal (that is on the pic as well as my configuration of NetBeans). https://i.sstatic.net/6WRh3.png

Solution

First, better replace your statement (in your program above)

printf( “Couldn't open the file.\n" );

with

perror(argv[1]);

then, simply compile your program in your terminal, e.g. type there a shell command similar to

gcc -Wall -g mysource.c -o myprog

^{(Read more about invoking GCC: the -Wall option asks for nearly all warnings and is very useful -so never miss it-; you could even add -Wextra to get even more warnings; the -g is asking for DWARF debugging information in the ELF executable and enables you to use later gdb)}

assuming your source code is in a file named mysource.c in the current working directory (use pwd command to query that current directory, ls -al to list it, and cd builtin command to change it)

at last, run your program as

./myprog sometestfile.txt

You might want to use the debugger. Read first about GDB, and try perhaps

gdb ./myprog

^{(I am guessing you are on Linux or some other POSIX compliant operating system, and using GCC compiler)}

Later, you'll want to have some bigger program of yours made in several translation units, having some common header file (to be #included in all of them). Then you'll use a builder like GNU make. You could use a good editor like emacs, some version control like git, etc...

^{(you might realize that NetBeans is not very useful, because you can have even better developing comfort with your own collection of tools; having the freedom to choose your tools is worthwhile!)}

PS. Perhaps replace printf( "%c", x ); with the shorter and more efficient putchar(x); ...