topic Checking using an external file in use in SAS Programming

Checking using an external file in use

LineMoon — Wed, 08 Jun 2016 22:22:48 GMT

Hello Experts,

In action 1 : I zip a file toto in toto.zip

In action 2: I unzip a file toto.zip in test

Before doing the action 2, I would to check if the file toto.zip is not in use.

Thank you

Re: Checking using an external file in use

ChrisNZ — Thu, 09 Jun 2016 05:00:39 GMT

The easiest way to do this is to try and rename the file. If the rename action works, then the file is not locked.

Another way is try and FOPEN() or MOPEN() the file.

Re: Checking using an external file in use

Kurt_Bremser — Thu, 09 Jun 2016 05:52:10 GMT

@ChrisNZ wrote:

The easiest way to do this is to try and rename the file. If the rename action works, then the file is not locked.

Another way is try and FOPEN() or MOPEN() the file.

Won't work on UNIX. Since in UNIX, file metadata (location on disk, permissions, timestamps) is stored in the inode, and the filename(s) in the directories, a rename can be done while a file is in use. One can even remove (unlink) a file that is in use, something I use to avoid "file is locked by another user" issues.

In UNIX, one should use the fuser commandline tool to determine if processes have a file handle on the file (inode) in question.

Re: Checking using an external file in use

ChrisNZ — Thu, 09 Jun 2016 06:25:13 GMT

@Kurt_Bremser I assume we have a windows user here, but you are right, Unix is different. The functions should work on unix too though, shouldn't they?

Re: Checking using an external file in use

Kurt_Bremser — Thu, 09 Jun 2016 07:18:43 GMT

The functions will work on UNIX, but you would need to specify at least APPEND mode for FOPEN/MOPEN to force an error if the file is opened by another process.