[GHC] #3199: System.Environment provides no access to argv[0]

[GHC]

#3199: System.Environment provides no access to argv[0]
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Reporter:  guest             |          Owner:                  
    Type:  bug               |         Status:  new             
Priority:  normal            |      Component:  libraries/base  
 Version:  6.10.2            |       Severity:  normal          
Keywords:                    |       Testcase:                  
      Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
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 The docs for `getProgName` say:

   Computation getProgName returns the name of the program as it was
 invoked.

   However, this is hard-to-impossible to implement on some non-Unix OSes,
 so instead, for maximum portability, we just return the leafname of the
 program as invoked. Even then there are some differences between
 platforms: on Windows, for example, a program invoked as foo is probably
 really FOO.EXE, and that is what getProgName will return.

 I think the "just return the leafname" part is stupid, because it means
 there is no way for me to get at C's `argv[0]`. How does mangling
 `argv[0]` increase portability? It just makes Haskell incompatible with
 everything else out there. Also, if your platform has `argv[0]`, you might
 as well return it as-is.

 Why do I want `argv[0]` at all? Well, the ability to write a drop-in
 replacement for a C program that does something like `fprintf(stderr, "%s:
 %s: %s\n", argv[0], filename, strerror(errno))` would be nice (where
 "drop-in" = character for character the same output). My current project
 is an IRC bot that can restart itself via `exec()`, preserving state in
 its command line arguments. However, I usually don't "install" the bot, I
 just run it from some directory. In this case `argv[0]` would be perfect:
 if it contains slashes, the bot was run from some directory (and `exec()`
 will find it there); if it doesn't, the executable was found in the path
 (and `exec()` will find that too).

 To summarize: I think the inability to get at argv[0] from Haskell is a
 bug. If you don't want to change `getProgName`, please consider adding
 another function (`getNativeProgName`?).

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/3199>
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