Process argc and argv outside of main()

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If I want to keep the bulk of my code for processing command line arguments out of main (for organization and more readable code), what would be the best way to do it?

void main(int argc, char* argv[]){
    //lots of code here I would like to move elsewhere
}

Either pass them as parameters, or store them in global variables. As long as you don't return from main and try to process them in an atexit handler or the destructor of an object at global scope, they still exist and will be fine to access from any scope.

For example:

// Passing them as args:
void process_command_line(int argc, char **argv)
{
    // Use argc and argv
    ...
}

int main(int argc, char **argv)
{
    process_command_line(argc, argv);
    ...
}

Alternatively:

// Global variables
int g_argc;
char **g_argv;

void process_command_line()
{
    // Use g_argc and g_argv
    ...
}

int main(int argc, char **argv)
{
    g_argc = argc;
    g_argv = argv;
    process_command_line();
    ...
}

Passing them as parameters is a better design, since it's encapsulated and let's you modify/substitute parameters if you want or easily convert your program into a library. Global variables are easier, since if you have many different functions which access the args for whatever reason, you can just store them once and don't need to keep passing them around between all of the different functions.

Process argc and argv outside of main(), Process argc and argv outside of main(). argc and argv in c c command line arguments string example what does argc and argv indicate in command line  We can also pass arguments to the main function and the main function can accept two arguments. One of these arguments is an integer and the second is an array of strings. Here, argc ( arg ument c ount) stores the number of the arguments passed to the main function and argv ( arg ument v ector)

One should keep to standards wherever practical. Thus, don't write

void main

which has never been valid C or C++, but instead write

int main

With that, your code can compile with e.g. g++ (with usual compiler options).

Given the void main I suspect a Windows environment. And anyway, in order to support use of your program in a Windows environment, you should not use the main arguments in Windows. They work in *nix because they were designed in and for that environment; they don't in general work in Windows, because by default (by very strong convention) they're encoded as Windows ANSI, which means they cannot encode filenames with characters outside the user's current locale.

So for Windows you better use the GetCommandLine API function and its sister parsing function. For portability this should better be encapsulated in some command line arguments module. Then you need to deal with the interesting problem of using wchar_t in Windows and char in *nix…

Anyway, I'm not sure of corresponding *nix API, or even if there is one, but google it. In the worst case, for *nix you can always initialize a command line arguments module from main. The ugliness for *nix stems directly from the need to support portability with C++'s most non-portable, OS-specific construct, namely standard main.

Process argc and argv outside of main() - c++ - android, int main(int argc, char **argv) { process_command_line(argc, argv); } Alternatively: // Global variables int g_argc; char **g_argv; void process_command_line()  int main( int argc, char* argv[], char* envp[]); int wmain( int argc, wchar_t* argv[], wchar_t* envp[]); The argument definitions are as follows: argc An integer that contains the count of arguments that follow in argv. The argc parameter is always greater than or equal to 1. argv

Simply pass argc and argv as arguments of the function in which you want to process them.

void parse_arg(int argc, char *argv[]);

Program Arguments (The GNU C Library), int main (int argc , char * argv []). The command line arguments are the whitespace-separated tokens given in the shell command used to invoke the program;  int main( int argc, char *argv[] ) { Here argc means argument count and argument vector. The first argument is the number of parameters passed plus one to include the name of the program that was executed to get those process running. Thus, argc is always greater than zero and argv[0] is the name of the executable (including the path) that was run to begin this process. For example, if we run

Check out the "getoptlong" family of functions and libraries. These offer a structured way of defining the arguments your program expects and can then parse them readily for you. Can also help with the generation of documentation / help responses.

It's an old library in the UNIX world, and there is a .Net implementation in C# too. (+ Perl, Ruby, & probably more. Nice to have a single paradigm usable across all of these! Learn once, use everywhere!)

C - Command Line Arguments, The command line arguments are handled using main() function arguments where argc refers to the number of arguments passed, and argv[] is a pointer array  int main (int argc, char *argv[]) Here, argc parameter is the count of total command line arguments passed to executable on execution (including name of executable as first argument). argv parameter is the array of character string of each command line argument passed to executable on execution.

Linux provides program_invocation_name and program_invocation_name_short.

C Language, argv[] outside of main()?, and *argv[] parameters of main) outside of the main function? Have main pass argc and argv to any other function you want. Is there process(); return 0; } However, if you can change the code in main() then doing this is >  The command line arguments are handled using main() function arguments where argc refers to the number of arguments passed, and argv[] is a pointer array which points to each argument passed to the program. When the above code is compiled and executed with single argument, it produces the following result.

ABC++ - Lesson 11 - Command Lines, ex11-1 hello testing one two argc=5 argv[1]=hello argv[2]=testing argv[3]=one as taking two arguments, one to hold the number of strings passed to main(), and Example ex11-3 is an extended example of command line argument processing. is accessible by all program functions, by declaring them outside the main  Basically argc and argv are not keywords, which is general impression. The function main() can take arguments, in the same way other functions take. So argc and argv are arguments, taken by the function main(). So from where one can send arguments to main function.

Command-line Arguments: main( int argc, char *argv[] ), In Unix, when you pass additional arguments to a command, those commands must be passed to the executing process. For example, in calling ls -al,  You should pass pointers to the main argc and argv variables so that GStreamer can process its own command line options, as shown in the following example. Initializing the gstreamer library int main (int argc, char *argv[]) { // initialize the GStreamer library gst_init (&argc, &argv);

Command line arguments in C/C++, To pass command line arguments, we typically define main() with two from outside instead of hard coding those values inside the code. argv[argc] is a NULL​  argc tells you how many command-line arguments there were. It is always at least 1, because the first string in argv (argv[0]) is the command used to invoke the program.argv contains the actual command-line arguments as an array of strings, the first of which (as we have already discovered) is the program's name.

Comments
  • I whole-heartedly agree with int main over void main. However, the other commentary leaves me … bemused. Which system other than Windows has a problem with the standard C++ convention for main()? I'm not aware of one, so castigating the standard convention as 'non-portable' and 'OS-specific' seems OTT.
  • @JonathanLeffler: I'm not aware of any commonly used system other than Windows where the main arguments don't work (other than for English alphabet pure ASCII text). Still, a feature that doesn't work in Windows is non-portable, and a feature designed for Unix-land is OS-specific. And the main arguments convention both doesn't work in Windows (i.e. is non-portable), and is designed for Unix-land (i.e. is OS-specific), and those two aspects are strongly connected. There's absolutely nothing amusing about it. I can only think of ugly political reasons for its persistence.