Does anyone know a good reference to cite for this information? Like the details of TCP, I think this is something better explained by an external reference than in the Racket reference manual.
Meanwhile, I'll look into smoothing the path from functions like `with-output-to-file' to information about the `exists' values. At Wed, 24 Aug 2011 17:23:52 +0200, Stephan Houben wrote: > Hi Marijn, > > At least on Unix/Linux, a file (inode) has some distinct identity > apart from its content. > > If a file is truncated, this is observed by all processes which have the file > open. In addition, all hard-links to the file are also truncated (since > these are just references to the same inode). > > If a file is replaced, the old inode is unaffected: processes which > had the file open continue to see the old data, other hard links > keep referring to the old file. > > If you don't care about these subtleties you can use truncate/replace. > > must-truncate is, I think, mostly useful if the file is to be used > for some form of inter-process communication. must-replace doesn't seem > useful in any way to me and moreover cannot be implemented reliably > without introducing a race condition between checking for existence of > the file and overwriting it with a new one. > > Stephan > > On 08/24/2011 03:01 PM, Marijn wrote: > > -----BEGIN PGP SIGNED MESSAGE----- > > Hash: SHA1 > > > > Hi, > > > > In the reference in section 12.1.5 File Ports[1], open-output-file is > > defined as having an optional keyword argument #:exist which can have > > one of 8 different values. The same options are used for a number of > > wrapper functions, among which with-output-to-file[2]. > > If you go to [2] you need to follow 3 internal links to similar > > functions to get to open-output-file[1] to find out what the different > > values of the #:exists argument mean. I think it would be good if a link > > was inserted such that you can go straight there. > > Unfortunately I find some of the explanations not so clear. I will > > comment on the explanation of each option in the order they appear in > > the docs. > > 1) error: this one is clear > > 2) replace: how is this different from 3) truncate? > > 3) truncate: see 2) > > 4) must-truncate: what about must-replace? > > 5) truncate/replace: clear if 2) and 3) are clarified > > 6) update: what is the current read/write position (this is hinted at in > > 8), but should really be explained fully here) and what happens when you > > write to the file (does it overwrite, insert, either depending on some > > other option)? > > 7) can-update: clear if 6) clarified > > 8) append: why is it only equivalent to update on Windows? > > > > Marijn > > > > > > > [1]:http://docs.racket-lang.org/reference/file-ports.html?#%28def._%28%28lib._ra > cket/private/base..rkt%29._open-output-file%29%29 > > > [2]:http://docs.racket-lang.org/reference/file-ports.html?#%28def._%28%28lib._ra > cket/private/base..rkt%29._with-output-to-file%29%29 > > -----BEGIN PGP SIGNATURE----- > > Version: GnuPG v2.0.17 (GNU/Linux) > > Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ > > > > iEYEARECAAYFAk5U9jIACgkQp/VmCx0OL2wy8ACbBPOVfHYF53NTCkY/9qXnbeyP > > AIAAn3J0URrJsIIZZiVIh/EOGqOBBJrX > > =rLk7 > > -----END PGP SIGNATURE----- > > _________________________________________________ > > For list-related administrative tasks: > > http://lists.racket-lang.org/listinfo/users > > > _________________________________________________ > For list-related administrative tasks: > http://lists.racket-lang.org/listinfo/users _________________________________________________ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
