getopt.h: Compiling Linux C-Code in Windows

Question

I am trying to get a set of nine *.c files (and nine related *.h files) to compile under Windows.

The code was originally designed in Linux to take command line arguments using the standard GNU-Linux/C library "getopt.h". And that library does not apply to building the C-code in Windows.

I want to ignore what my code does right now and ask the following question. For those of you familiar with this C-library "getopt.h": will it be possible to build and run my code in Windows if it depends on POSIX-style command-line arguments? Or will I have to re-write the code to work for Windows, passing input files differently (and ditching the "getopt.h" dependency)?

if MSVC support is not a hard requirement, there's always MinGW: I'm quite happy with the MinGW cross-compiler packages which come with Cygwin... — Christoph
– Christoph, Commented May 1, 2012 at 21:28
getopt.h discribes the API provided by methods from getopt.c. Pull it from somewhere, compile it and link the result to your app and your done. — alk
– alk, Commented May 1, 2012 at 21:40
Just a nit regarding alk's comment, it can be done, technically, but the legality depends entirely on the compatibility of the license(s) from the getopt sources (if any), and those of the project. Some getopt implementations say public domain, so that would likely be no problem. — user2895783
– user2895783, Commented Mar 18, 2017 at 15:56

jimifiki · Accepted Answer · 2014-07-29 08:29:12Z

getopt() is actually a really simple function. I made a github gist for it, code from here is below too

#include <string.h>
#include <stdio.h>

int     opterr = 1,             /* if error message should be printed */
  optind = 1,             /* index into parent argv vector */
  optopt,                 /* character checked for validity */
  optreset;               /* reset getopt */
char    *optarg;                /* argument associated with option */

#define BADCH   (int)'?'
#define BADARG  (int)':'
#define EMSG    ""

/*
* getopt --
*      Parse argc/argv argument vector.
*/
int
  getopt(int nargc, char * const nargv[], const char *ostr)
{
  static char *place = EMSG;              /* option letter processing */
  const char *oli;                        /* option letter list index */

  if (optreset || !*place) {              /* update scanning pointer */
    optreset = 0;
    if (optind >= nargc || *(place = nargv[optind]) != '-') {
      place = EMSG;
      return (-1);
    }
    if (place[1] && *++place == '-') {      /* found "--" */
      ++optind;
      place = EMSG;
      return (-1);
    }
  }                                       /* option letter okay? */
  if ((optopt = (int)*place++) == (int)':' ||
    !(oli = strchr(ostr, optopt))) {
      /*
      * if the user didn't specify '-' as an option,
      * assume it means -1.
      */
      if (optopt == (int)'-')
        return (-1);
      if (!*place)
        ++optind;
      if (opterr && *ostr != ':')
        (void)printf("illegal option -- %c\n", optopt);
      return (BADCH);
  }
  if (*++oli != ':') {                    /* don't need argument */
    optarg = NULL;
    if (!*place)
      ++optind;
  }
  else {                                  /* need an argument */
    if (*place)                     /* no white space */
      optarg = place;
    else if (nargc <= ++optind) {   /* no arg */
      place = EMSG;
      if (*ostr == ':')
        return (BADARG);
      if (opterr)
        (void)printf("option requires an argument -- %c\n", optopt);
      return (BADCH);
    }
    else                            /* white space */
      optarg = nargv[optind];
    place = EMSG;
    ++optind;
  }
  return (optopt);                        /* dump back option letter */
}

I have this included in my project, however when I try to use optarg it says that it is undeclared in Windows. The return value of getopt is always the opt. How can I use optarg?
The header file is missing extern char *optarg; and extern int optind, opterr, optopt;

Adam Rosenfield · Accepted Answer · 2012-12-18 22:53:06Z

28

You are correct. getopt() is POSIX, not Windows, you would generally have to re-write all command-line argument parsing code.

Fortunately, there is a project, Xgetopt, that is meant for Windows/MFC classes.

http://www.codeproject.com/Articles/1940/XGetopt-A-Unix-compatible-getopt-for-MFC-and-Win32

If you can get this working in your project, it should save you a fair bit of coding and prevent you from having to rework all parsing.

Additionally, it comes with a nice GUI-enabled demo app that you should find helpful.

Good luck!

edited Dec 18, 2012 at 22:53

Adam Rosenfield

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answered May 1, 2012 at 21:20

Cloud

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5 Comments

john_science Over a year ago

I will give that a try right now. But I cannot tell from the link you showed: is the API for this library the same as the old getopt API?

alk Over a year ago

Could you name any reason to do a re-write, but doing parsing exercises?

john_science Over a year ago

Well, the code I am porting over (for use in a much larger system) is a few months old. But the people developing it are as much scientists as engineers, so they don't usually use the newest compilers or even the newest versions of UNIX/LINUX. So if they are doing things in an old-fashioned way, that wouldn't surprise me.

alk Over a year ago

'a few month` :-) no issues with getopt being to young or even to mature... you might very well give it a try a pull the getopt sources from the links in my answer and use them.

john_science Over a year ago

@Dogbert That was almost the perfect solution. Except I am having a really annoying time trying to run the library you linked (which is C++) with the code base I currently have (which is C). I have not yet given up that this will be possible, but mixing the two language flavors seems to add some complexity to Visual Studio builds.

akks · Accepted Answer · 2013-06-10 09:38:02Z

8

There is a possibilty to use code from MinGW runtime (by Todd C. Miller):

http://sourceforge.net/apps/trac/mingw-w64/browser/trunk/mingw-w64-crt/misc

I have created a small library with these files and CMake script (can generate a VS project):

https://github.com/alex85k/wingetopt

answered Jun 10, 2013 at 9:38

akks

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3 Comments

john_science Over a year ago

It looks like your library would have been really helpful. I just wanted to say. But I saw Dogbert's comment about Xgetopt first and that did the trick. Thanks, though!

namezero Over a year ago

Thanks. That works copy and paste for a quick port to use a program really quick

Toby Speight Dec 16, 2024 at 22:24

Whilst this may theoretically answer the question, it would be preferable to include the essential parts of the answer here, and provide the link for reference.

NullUserException · Accepted Answer · 2017-12-11 22:13:33Z

5

I did compile the getopt code under windows.

I did this as I wanted to explicilty use its command line parsing functionality in a windows (command line) app.

I successfully did this using VC2010.

As far as I remember I ran into no significant issues doing so.

getopt.c getoptl.c

edited Dec 11, 2017 at 22:13

NullUserException

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answered May 1, 2012 at 21:34

alk

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4 Comments

Michael Petrotta Over a year ago

A suggested edit added the sentence "Please note, that this specific code is covered by the GPLv3 and not by the LGPL." to this answer. I rolled that back, and include the comment here.

Victor Sergienko Over a year ago

Er, including getopt.in.h?

alk Over a year ago

@VictorSergienko: Sure some code out of getopt.in.h was necessary to compile getopt's sources. Anyway, my answer was not meant to be understood the way that compiling the files linked was possible without any (minor) modifications. Just feeding them "as is" to VC10 would not work.

jifb Over a year ago

There's also getopt.c in github.com/berkeleydb/libdb/blob/master/src/clib/getopt.c which is meant to compile for various operating systems. It has BSD 3-Clause license.

bowman han · Accepted Answer · 2014-09-09 09:06:33Z

2

if you just want getopt to be used in visual c++ without other dependences, I have port the getopt.c from latest gnu libc 2.12, with all new features.The only difference is you have to use TCHAR instead of char,but This is very common in windows.

simply download the source, make, copy libgetopt.lib and getopt.h getopt_int.h to your project.

you can also make it using CMakeList.txt in the root dir.

download the source from github

edited Sep 9, 2014 at 9:06

answered Sep 9, 2014 at 8:33

bowman han

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Comments

Conor Hyde · Accepted Answer · 2024-12-16 08:46:00Z

2

The latest getopt portable implementation written by mingw-w64 project is on:

https://sourceforge.net/p/mingw-w64/mingw-w64/ci/master/tree/mingw-w64-crt/misc/getopt.c https://sourceforge.net/p/mingw-w64/mingw-w64/ci/master/tree/mingw-w64-headers/crt/getopt.h

Just compile the getopt.c with your code's target object together. I've tried it on Visual Studio 2022 CMake Project and it works fine.

answered Dec 16, 2024 at 8:46

Conor Hyde

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Comments

rnordeen · Accepted Answer · 2014-01-15 19:49:30Z

You might try looking into glib-2.0 as an alternative. It would be a bit large for just needing an option parser. The up side would be having access to all the other wonderful toys in the glib.

Just to be honest, I haven't tried getting this to work (I stick mostly to Linux), so YMMV.

Getting glib to work in windows: HowTo

Oh, you might explore using mingw for the build environment, and visual studio for your IDE.

Glib for Win32: HowTo

Anywho, hope this helps.

Steven Fosdick · Accepted Answer · 2020-04-27 12:18:53Z

From my reading of the documentation the header file getopt.h is specific to the GNU C library as used with Linux (and Hurd). The getopt function itself has been standardised by POSIX which says it should be declared, along with optind optarg etc. in unistd.h

I can't try this on Visual Studio myself but it would be worth checking if unistd.h exists and declares this function as Visual Studio does provides some other POSIX functions.

If not, then I'd definitely grab an implementation of getopt rather than re-write the argument parsing to work without it. Getopt was written to make things easier for the programmer and more consistent for user of programs with command line arguments. Do check the license, though.

Benj · Accepted Answer · 2012-05-01 21:22:17Z

-1

From what I remember of getopt.h, all it does is provide a handy parser for processing argv from your main function:

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

Windows console programs still have a main method, so you can simply loop through your argv array and parse the parameters yourself. e.g.

for ( int i = 1; i < argc; i++ )
{
  if (!strcmp(argv[i], "-f"))
    filename = argv[++i];
}

answered May 1, 2012 at 21:22

Benj

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4 Comments

john_science Over a year ago

Thanks! I'm not sure if this will be practical for me. While I understand I could scroll through the ~5000 lines of code and re-write these bits, this is code that we are getting from other developers. So, what happens in 2 months when they give us a slightly newer version of the code? Will I have to redo the argument processing code every time we get an update? That sounds time consuming.

Benj Over a year ago

It sounds as though you need to get together with these other developers and agree an argument passing system which is portable. The solution provided by @theJollySin may well be the answer, but either way it's not difficult to write a portable argument parser.

alk Over a year ago

Over the time the getopt API looked quiet stable to me. @theJollySin

bobobobo Over a year ago

Why do it manually when the getopt function is available on the internet?

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