How to Access Command Line Arguments

How do I access command line arguments?

Python tutorial explains it:

import sys

print(sys.argv)

More specifically, if you run python example.py one two three:

>>> import sys
>>> print(sys.argv)
['example.py', 'one', 'two', 'three']

How can I access command line parameters in Rust?

You can access the command line arguments by using the std::env::args or std::env::args_os functions. Both functions return an iterator over the arguments. The former iterates over Strings (that are easy to work with) but panics if one of the arguments is not valid unicode. The latter iterates over OsStrings and never panics.

Note that the first element of the iterator is the name of the program itself (this is a convention in all major OSes), so the first argument is actually the second iterated element.

An easy way to deal with the result of args is to convert it to a Vec:

use std::env;

fn main() {
    let args: Vec<_> = env::args().collect();
    if args.len() > 1 {
        println!("The first argument is {}", args[1]);
    }
}

You can use the whole standard iterator toolbox to work with these arguments. For example, to retrieve only the first argument:

use std::env;

fn main() {
    if let Some(arg1) = env::args().nth(1) {
        println!("The first argument is {}", arg1);
    }
}

You can find libraries on crates.io for parsing command line arguments:

• docopt: you just write the help message, and the parsing code is generated for you.
• clap: you describe the options you want to parse using a fluent API. Faster than docopt and gives you more control.
• getopts: port of the popular C library. Lower-level and even more control.
• structopt: built on top of clap, it is even more ergonomic to use.

Accessing command line arguments in C

The first argument to the program is the name of the program itself. Try using the following instead.

int a = atoi(argv[1]); 
int b = atoi(argv[2]); 

How to access command line arguments in .csx script?

Environment.GetCommandLineArgs() returns ["csi", "script.csx", "2000"] for that example.

MS Access, How to determine the command line parameters that the current instance of application has started with?

I don’t believe you can get the full command line used to start Access. However, you can certainly add a /cmd option to the startup swtichs, and VBA "command()" will return these values.

thus:
The VBA function command() will return the values after the /cmd

Thus:

A typical startup command line would look like:

"C:\Program Files (x86)\Microsoft Office\Office14\MSACCESS.EXE"
"c:\MyCoolProgram\MyApp.accde" /runtime /cmd "Parm1" "Parm2"

The above would be all one line (with a space between). To grab the two passed parms, then

Debug.Print Split(Command(), " ")(0)
Debug.Print Split(Command(), " ")(1)

You can also test if the application was launched with /runtime switch, or that you using the runtime version with this:

If syscmd(acSysCmdRuntime) = true then
   ' runtime version

So you can specify and pass startup parameters with the /cmd startup swtich

How to access command line arguments of the caller inside a function?

My reading of the Bash Reference Manual says this stuff is captured in BASH_ARGV,
although it talks about "the stack" a lot.

#!/bin/bash

shopt -s extdebug

function argv {
  for a in ${BASH_ARGV[*]} ; do
    echo -n "$a "
  done
  echo
}

function f {
  echo f $1 $2 $3
  echo -n f ; argv
}

function g {
  echo g $1 $2 $3
  echo -n g; argv
  f
}

f boo bar baz
g goo gar gaz

Save in f.sh

$ ./f.sh arg0 arg1 arg2
f boo bar baz
fbaz bar boo arg2 arg1 arg0
g goo gar gaz
ggaz gar goo arg2 arg1 arg0
f
fgaz gar goo arg2 arg1 arg0

How can I access the command line arguments in a console application using IHostedService?

I don't believe there's a built-in DI method to get command-line arguments - but probably the reason that handling command-line arguments is the responsibility of your host application and that should be passing host/environment information in via IConfiguration and IOptions etc.

Anyway, just define your own injectables:

public interface IEntrypointInfo
{
    String CommandLine { get; }

    IReadOnlyList<String> CommandLineArgs { get; }

    // Default interface implementation, requires C# 8.0 or later:
    Boolean HasFlag( String flagName )
    {
        return this.CommandLineArgs.Any( a => ( "-" + a ) == flagName || ( "/" + a ) == flagName );
    }
}

/// <summary>Implements <see cref="IEntrypointInfo"/> by exposing data provided by <see cref="System.Environment"/>.</summary>
public class SystemEnvironmentEntrypointInfo : IEntrypointInfo
{
    public String CommandLine => System.Environment.CommandLine;

    public IReadOnlyList<String> CommandLineArgs => System.Environment.GetCommandLineArgs();
}

/// <summary>Implements <see cref="IEntrypointInfo"/> by exposing provided data.</summary>
public class SimpleEntrypointInfo : IEntrypointInfo
{
    public SimpleEntrypointInfo( String commandLine, String[] commandLineArgs )
    {
        this.CommandLine = commandLine ?? throw new ArgumentNullException(nameof(commandLine));
        this.CommandLineArgs = commandLineArgs ?? throw new ArgumentNullException(nameof(commandLineArgs));
    }

    public String CommandLine { get; }

    public IReadOnlyList<String> CommandLineArgs { get; }
}

//

public static class Program
{
    public static async Task Main( String[] args )
    {
        await Host.CreateDefaultBuilder( args )
            .UseContentRoot(Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location))
            .ConfigureServices((context, services) =>
            {
                services.AddHostedService<ConsoleHostedService>();
                services.AddSingleton<IEntrypointInfo,SystemEnvironmentEntrypointInfo>()
            })
            .RunConsoleAsync();
    }

For automated unit and integration tests, use SimpleEntrypointInfo.

---

Related Topics