Handling command line flags in C/C++

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I am looking for a very simple explanation/tutorial on what flags are. I understand that flags work indicate a command what to do. For example:

rm -Rf test

I know that the rm command will remove the test folder and that the -Rf flags will force the command to erase not just the folder but the files in it.

But, where are the flags read/compiled??? What handles the flags? Can I, for example, write my own C/C++ program and designate different flags so that the program does different things? I hope I am asking the right questions. If not, please let me know.

This simple program should demonstrate the arguments passed to the program (including the program name itself.)

Parsing, interpreting and using those arguments is up to the programmer (you), although there are libraries available to help:

int main(int argc, char* argv[])
    int i;
    for(i=0; i<argc; ++i)
    {   printf("Argument %d : %s\n", i, argv[i]);
    return 0;

If you compile this program into a.out, and run it as:

prompt$>  ./a.out ParamOne ParamTwo -rf x.c

You should see output:

Argument 0 : a.out
Argument 1 : ParamOne
Argument 2 : ParamTwo
Argument 3 : -rf
Argument 4 : x.c

C Tutorial – Command Line Parameter Parsing � CodingUnit , Command-line parameters can be used for many things. Let's take a look at another example that will print different things depending on the flags given. If the –f� In your own C program you can process command line options in any way you see fit. Command line parameters in C come in the parameters of the main(int argc, char *argv[]) method as strings. And if you'd like to process command line parameters in a way similar to most UNIX commands, the function you're probably looking for is getopt()

getopt() function in C to parse command line arguments , The getopt() function is a builtin function in C and is used to parse command line arguments. Syntax: getopt(int argc, char *const argv[], const char *optstring)� Listed below are the command line available in Csound5 organized by categories. Various platform implementations may not react the same way to different flags! You can view the command line flags organized alphabetically in Command-line Flags (Alphabetically). The format of a command is either:

Actually you can write your own C++ programm which accepts commandline parameters like this:

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

The variable argc will contain the number of parameters, while the char* will contain the parameters itself.

You can dispatch the parameters like this:

for (int i = 1; i < argc; i++)
    if (i + 1 != argc)
        if (strcmp(argv[i], "-filename") == 0) // This is your parameter name
            char* filename = argv[i + 1];    // The next value in the array is your value
            i++;    // Move to the next flag

C - Command Line Arguments, C - Command Line Arguments - It is possible to pass some values from the The command line arguments are handled using main() function arguments where� The has_arg field can be set to no_argument, required_argument or optional_argument, which correlate to the values 0, 1, and 2. The flag pointer, will be set to val on a match and getopt_long () will return 0. If flag is NULL, val will be what getopt_long () returns when the long option is matched.

In your own C program you can process command line options in any way you see fit. Command line parameters in C come in the parameters of the main(int argc, char *argv[]) method as strings.

And if you'd like to process command line parameters in a way similar to most UNIX commands, the function you're probably looking for is getopt()

Good luck!

How to parse command line parameters., Adding the ability to parse command-line parameters to a program is very easy. Every C and C++ program has a main function. In a program� It may also contain the file name and line number of the file from which the options were parsed in case a list file or option file was specified on the command line and the OptionStyles.File flag was enabled in the parser. See the API documentation for more information on this. 5.4 Generating Usage Information

The easiest thing is to write your main() like so:

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

Then inside that main you decide what happens to the command line arguments or "flags". You find them in argv and their number is argc.

Parsing command line arguments from C - Yakking, command-line parser you can set optind back to the index of argv you want to parse, so set it to 1 to rewind back to the beginning. /* test.c */ #include <stdio.h> � Note. To enable command-line arguments in the Main method in a Windows Forms application, you must manually modify the signature of Main in program.cs.The code generated by the Windows Forms designer creates a Main without an input parameter.

CS 11: C track: processing command-line arguments, The C language has fairly standardized conventions about how to process command-line arguments, which I summarize here. I will also give some advice on� cc myfile.c. Compile the file myfile.c. Output will be written to the executable file a.out. cc myfile.c -o myexe. Compile the file myfile.c and name the compiled executable output file myexe. cc myfile.c -Wall -o myexe. Compile the file myfile.c and output the compiled executable as myexe, displaying warnings during compilation if they occur.

Parsing Program Arguments (The GNU C Library), 2 Parsing Program Arguments. If the syntax for the command line arguments to your program is simple enough, you can simply pick the arguments off� Command-line parameters are passed to a program at runt-time by the operating system when the program is requested by another program, such as a command interpreter ("shell") like cmd.exe on Windows or bash on Linux and OS X. The user types a command and the shell calls the operating system to run the program.

How to get command line flags or options in an executable , In C or C++ you can simply convert the first argument "10" or whatever it is, to an integer. All command line arguments are strings ( char arrays� CODE EXAMPLE You can access command-line arguments, including the program name and flags, through the os.Args variable.

  • Up till your last paragraph this didn't look like a Stack Overflow question, but it actually is. It's very basic, and you've tagged it wrong, but it's a valid question.
  • google "c command line arguments"
  • On the line 3, you are comparing pointers, not strings... It should rather be: if ( strcmp( argc[i], "-filename") == 0) {
  • getopt is pretty ancient. argp_parse is a reasonable replacement, and there are many option parsing libraries available (eg libpopt).