Re: dbmopen() test if file exists already?

Since I don't think there's a function to test for the existence of a dbm file you could either try a test dbmopen or a glob e.g

warn "dbm exists" if dbmopen(my %hash, "your_data");
warn "dbm_exists" if glob('your_data.{pag,db,dir}');
[download]

But since dbmopen doesn't clobber the data this test seems rather frivolous.
HTH

_________ broquaint

Comment on Re: dbmopen() test if file exists already? Download Code

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•Re: Re: dbmopen() test if file exists already? by merlyn (Sage) on May 28, 2003 at 11:42 UTC
`warn "dbm_exists" if glob('your_data.{pag,db,dir}');` [download] There's no promise that this syntax is portable, even to all Unix systems. On versions of Perl prior to 5.6, where `glob` was a callout to a separate shell process, and a csh-like shell was not available, the Bourne Shell was used, and this would definitely get a Bourne Shell upset. Of course, now that `glob` is internal, it's a lot more portable. -- Randal L. Schwartz, Perl hacker Be sure to read my standard disclaimer if this is a reply.	[reply] [d/l]
Re: Re: dbmopen() test if file exists already? by Cody Pendant (Prior) on May 28, 2003 at 12:53 UTC
`>since dbmopen doesn't clobber the data >this test seems rather frivolous.` [download] Didn't say it did. I was thinking about some data structure where, for example, user details could be stored in that kind of tied hash, and so you might want to check if you already had a "codypendant.db" or a "broquaint.db" when a new user came along, in case of duplication. I really should learn Tie::Hash shouldn't I? -- “Every bit of code is either naturally related to the problem at hand, or else it's an accidental side effect of the fact that you happened to solve the problem using a digital computer.” M-J D	[reply] [d/l]
Re: Re: Re: dbmopen() test if file exists already? by broquaint (Abbot) on May 28, 2003 at 13:13 UTC
I was thinking about some data structure where, for example, user details could be stored in that kind of tied hash, and so you might want to check if you already had a "codypendant.db" or a "broquaint.db" when a new user came along, in case of duplication. This sounds like a case for creating a single hash, where each user is a key, then it would just be a matter testing the existence of a user with `exists %user_db`. If however, you've decided to do it on a per file basis for whatever reason then it would just be a matter of testing the return status of `dbmopen` e.g `dbmopen(my %hash, "codypendant") and warn "codypendant already exists";` [download] HTH `_________ broquaint`	[reply] [d/l]