temporary file name, with a twist

temporary file name, with a twist

[nobrowser]

Hello,

in my lisp code, I need to get a unique temporary file name, but _with
a specific suffix_.  There doesn't seem to be a built-in or an easy
lispy way of doing this.  As for devious ways, on Debian there is the
tempfile program but I don't think this generalizes even to other Linux
distros.  Or I could use the maildir scheme:
${hostname}_${emacs_pid}_${timestamp}.${suffix}, but how to portably
get the hostname?  mail-host-name can't be used because the very point
is to distinguish between distinct host at the same site.

This must have been done before ...

Thanks,
i

Re: temporary file name, with a twist

[Miles Bader]

nobrowser@gmail.com writes:
> ${hostname}_${emacs_pid}_${timestamp}.${suffix}, but how to portably
> get the hostname?  mail-host-name can't be used because the very point
> is to distinguish between distinct host at the same site.

(system-name)

?

-Miles
-- 
Yo mama's so fat when she gets on an elevator it HAS to go down.

Re: temporary file name, with a twist

[nobrowser]

Miles Bader wrote:
> nobrowser@gmail.com writes:
> > ${hostname}_${emacs_pid}_${timestamp}.${suffix}, but how to portably
> > get the hostname?  mail-host-name can't be used because the very point
> > is to distinguish between distinct host at the same site.
>
> (system-name)
> 

Thanks.  One would think "apropos host" would work, but nooooooo ...

Re: temporary file name, with a twist

[Reiner Steib]

On Thu, Sep 07 2006, nobrowser@gmail.com wrote:

> in my lisp code, I need to get a unique temporary file name, but
> _with a specific suffix_.

`make-temp-file' or `make-temp-name'?

Bye, Reiner.
-- 
       ,,,
      (o o)
---ooO-(_)-Ooo---  |  PGP key available  |  http://rsteib.home.pages.de/

Re: temporary file name, with a twist

[nobrowser]

Reiner Steib wrote:
> On Thu, Sep 07 2006, nobrowser@gmail.com wrote:
>
> > in my lisp code, I need to get a unique temporary file name, but
> > _with a specific suffix_.
>
> `make-temp-file' or `make-temp-name'?
>

Nope, that's what I started with.  Doesn't do the suffix part.

I'll do the maildir thing, I suppose.

Re: temporary file name, with a twist

[David Kastrup]

nobrowser@gmail.com writes:

> Reiner Steib wrote:
>> On Thu, Sep 07 2006, nobrowser@gmail.com wrote:
>>
>> > in my lisp code, I need to get a unique temporary file name, but
>> > _with a specific suffix_.
>>
>> `make-temp-file' or `make-temp-name'?
>>
>
> Nope, that's what I started with.  Doesn't do the suffix part.

Emacs CVS has

make-temp-file is a compiled Lisp function in `files.el'.
(make-temp-file PREFIX &optional DIR-FLAG SUFFIX)

Create a temporary file.
The returned file name (created by appending some random characters at the end
of PREFIX, and expanding against `temporary-file-directory' if necessary),
is guaranteed to point to a newly created empty file.
You can then use `write-region' to write new data into the file.

If DIR-FLAG is non-nil, create a new empty directory instead of a file.

If SUFFIX is non-nil, add that at the end of the file name.

-- 
David Kastrup, Kriemhildstr. 15, 44793 Bochum

Re: temporary file name, with a twist

[Reiner Steib]

On Fri, Sep 08 2006, nobrowser@gmail.com wrote:

> Reiner Steib wrote:
>> On Thu, Sep 07 2006, nobrowser@gmail.com wrote:
>>
>> > in my lisp code, I need to get a unique temporary file name, but
>> > _with a specific suffix_.
>>
>> `make-temp-file' or `make-temp-name'?
>>
>
> Nope, that's what I started with.  Doesn't do the suffix part.

In addition to David's comment, I'd say it's not exactly hard to
append a suffix when using `make-temp-name'; at least easier than
creating maildir-like[1] names.

Bye, Reiner.

[1] BTW, maybe `gnus/nnmaildir.el' provides a function or code for
    this?
-- 
       ,,,
      (o o)
---ooO-(_)-Ooo---  |  PGP key available  |  http://rsteib.home.pages.de/

Re: temporary file name, with a twist

[nobrowser]

Reiner Steib wrote:
> On Fri, Sep 08 2006, nobrowser@gmail.com wrote:
>
> > Reiner Steib wrote:
> >> On Thu, Sep 07 2006, nobrowser@gmail.com wrote:
> >>
> >> > in my lisp code, I need to get a unique temporary file name, but
> >> > _with a specific suffix_.
> >>
> >> `make-temp-file' or `make-temp-name'?
> >>
> >
> > Nope, that's what I started with.  Doesn't do the suffix part.
>
> In addition to David's comment, I'd say it's not exactly hard to
> append a suffix when using `make-temp-name'; at least easier than
> creating maildir-like[1] names.

At the slight risk of further insulting a deceased equine, let me
explain:

either way, with make-temp-name or with handcrafted names, I have,
theoretically, the classic tmpnam(3) race condition.  The difference is
that with my own, I control the algorithm so I can be confident that
the race won't actually happen in practice.  I don't have that
confidence with the Emacs names, which for all I know are generated
with tmpnam.  The doc says only that "The Emacs process number forms
part of the result".  But how unique are they actually, what's the
length of the cycle?

Thanks,
i