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Re: Bare Bones Backup Button

  • To: mathgroup at smc.vnet.net
  • Subject: [mg111480] Re: Bare Bones Backup Button
  • From: Albert Retey <awnl at gmx-topmail.de>
  • Date: Tue, 3 Aug 2010 06:34:54 -0400 (EDT)
  • References: <i368lp$r56$1@smc.vnet.net>

Am 02.08.2010 13:03, schrieb Murray Eisenberg:
> An exchange reported in  between DrMajorBob and Selwyn Hollis 
> culminated, in essence, in the code below for creating a saveable 
> palette with a button to back up the InputNotebook.
> 
> If the target directory for the backup (fixed in the code that creates 
> the palette) already exists, then each time I click the button, I get an 
> unwanted message
> 
>    CreateDirectory::filex : ... already exists
> 
> in the Messages window.
> 
> What is the best way to modify the code so as avoid that message? I can 
> think of two methods:
> 
> (1) Include a separate test as to whether that directory already exists 
> and, if so, by-pass the CreateDirectory phase; or
> 
> (2) Somehow trap the CreateDirectory so as to eliminate the message.
> 
> For Method (1), how does one tell whether a directory exists? I don't 
> find a single function that does it. All I can see is to use first 
> FileExistsQ to see if there's some file with the target directory's name 
> and second, if the file exists, FileType to check that it's a directory. 
>   That seems to be getting unduly complicated.

I would just use FileType, the result can be Directory, File or None,
but you would just have to discriminate between None (create directory)
Directory (don't do anything) or everything else (issue warning):

Switch[FileType[dirname],
 None,CreateDirectory[dirname],
 Directory,Null,
 _, Message[...];Abort[]
]

> Method (2) in principle seems simpler, and perhaps wrapping Quiet around 
> the entire body of the Module (which is an extended If expression) would 
> do the trick. But this would also suppress other messages that one might 
> want to see, such as when the directory does not already exist but for 
> some reason cannot be created; or that the directory exists but for some 
> reason is not writable; etc.

Quiet accepts a second argument so you will see every message except the
ones mentioned in the second argument. This will only suppress the
CreateDirectory::filex-Messages:

Quiet[CreateDirectory[dirname],CreateDirectory::filex]

hth,

albert





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