Re: [Tcllib-devel] More file utilities ?

[Joe E. <jen...@fl...>]

Andreas Kupries wrote:

> 	touch PATH
> 		Creates empty file at PATH. Deletes any pre-existing
> 		file in this location.

For Unix users, "touch" would be a _very bad_ name for this operation --
the shell command `touch` only updates the modification time
of existing files, it doesn't truncate them.


> 	getfile PATH
> 		Returns contents of file. Assumes that file is text,
> 		and in system encoding.
> 	putfile PATH TEXT
> 		Writes text as the new content of the file.
> 		Note: Does _not_ add a traling \n to the data.

I usually call these "readFile" and "writeFile", after
the analogous Haskell Standard Prelude functions.


> 	insertat PATH AT DATA
> 		Inserts data at offset AT into the file.
>
> 	removeat PATH AT N
> 		Removes N characters from the file, starting at
> 		offset AT.

No comment on the names, but these operations would be
very useful to have in tcllib just so we'd have a short
answer when newbies ask how to do this (which seems to
come up once a month or so on c.l.t. :-)


> 	hack_file PATH KEY VAL ...
> 		Takes the list of keys and values and applies them to
> 		the contents of the file, via [string map].
>
> 	hack_file_copy PATHin PATHout KEY VAL ...
> 		Like hack_file, but writes the result to a different
> 		file.

These seem rather special-purpose.  A useful factor of the
first one might be:

	updateInPlace $filename $cmdPrefix --
	    Reads the contents of file $filename and passes it
	    as an additional argument to $cmdPrefix.  Overwrites
	    the original file with the return value of the command.
	    If the command raises an error, the original file
	    is not modified.

Then 'hack_file' could be expressed as:

	updateInPlace PATH [list string map [list KEY VAL...]]



--Joe English

  jen...@fl...