On 05/05/2015 01:43 PM, Vale Cofer-Shabica wrote:

Hello all,

Punchline first: What's the "best practice" way of doing unix-style command line argument and file input processing in Haskell?

Background: I'm using Haskell to write programs that act like well-behaved, pipe-friendly unix tools. i.e., the following are all equivalent:

% ./prog file % ./prog < file % cat file | ./prog

Thus far, I've done this by directly inspecting the first element of System.Environment.getArgs, which has been fine thus far.

I use CmdArgs for this. I think the simplest example is, https://hackage.haskell.org/package/email-validator And one with multiple modes: https://hackage.haskell.org/package/hath It's not *quite* what you asked for: I use e.g. `hath -i file` to mean the same thing as `hath < file`, but that's as close as I got.

Hi there, I've had fun using cmdargs[1]. Here are several sites that I found to be very helpful in learning how to use the package: - This was probably the single most helpful bit of example code[2] that I found because it illustrates how to have multiple modes that take different option flags better than other tutorials. - Neil Mitchell, the author of cmdargs, has some nice example[3] code[4] that is also useful for seeing how the library works. - Here is another an example[5] that shows how to make Hello World take a few basic command arguments. Hope this helps, -- Rianna Morgan rmorgan@trystero.is On Tue, May 5, 2015, at 10:43 AM, Vale Cofer-Shabica wrote:

Hello all,

Punchline first: What's the "best practice" way of doing unix-style command line argument and file input processing in Haskell?

Background: I'm using Haskell to write programs that act like well-behaved, pipe-friendly unix tools. i.e., the following are all equivalent:

% ./prog file ./prog < file cat file | ./prog

Thus far, I've done this by directly inspecting the first element of System.Environment.getArgs, which has been fine thus far.

I'd also like to be able to take simple command line arguments (boolean flags and numeric parameters) and the above doesn't adapt well to that case. I'd like to do this in the idiomatic, "standard" way (a la getopt() in C). Browsing through the wiki page on command line argument parsers [1] gave me a bewildering array of options. I'm not really sure where to start, though I remember reading a blanket endorsement of optparse-applicative somewhere.

Any pointers or examples that address my use-case would be much appreciated.

-vale

[1]: https://wiki.haskell.org/Command_line_option_parsers _______________________________________________ Beginners mailing list Beginners@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners

Links: 1. https://hackage.haskell.org/package/cmdargs 2. https://zuttobenkyou.wordpress.com/2011/04/19/haskell-using-cmdargs-single-a... 3. http://neilmitchell.blogspot.com/2010/08/cmdargs-example.html 4. http://community.haskell.org/~ndm/cmdargs/ 5. http://spin.atomicobject.com/2012/12/13/using-haskells-cmdargs-package/