Esteemed Monks,

Let me first try to describe the problem I am trying to solve:

I have a large file with many complex entries, each relating to a file in a Unix filestore tree.

I wish to extract a subset of these entries to match part of the current filestore tree; I can produce a list of the current filestore tree using the 'find' command.

So I have two files:

The true filestore list

/fred/myfile
/fred/myfile2
/bert/myfile

The large complex file

user ALLFILES /fred/myfile=/archive/dingbat/fred/myfile 3 6 9 thegoosedrankwine
user ALLFILES /fred/myfile2=/archive/dingbat/fred/myfile 3 6 9 thegoosedrankwine
user ALLFILES /fred/myfile3=/archive/dingbat/fred/myfile 3 6 9 thegoosedrankwine
user ALLFILES /bert/myfile=/archive/dingbat/fred/myfile 3 6 9 thegoosedrankwine
user ALLFILES /bert/myfile2=/archive/dingbat/fred/myfile 3 6 9 thegoosedrankwine

You will note that the third field (up to the '=') in the complex file is the filename in the real filestore tree.

My tentative plan is to set up the first file as a hash, indexed by the whole contents of each line, and then read serially through the second file, splitting out the file name component and matching it with the Hash.

If I get a hit, I then overwrite the matching entry in the Hash with the current line in my complex input file.

At the end I should have copied all the matching entries out of the complex file, and these should now be in the other file.

Any lines without a match will be unchanged.

So, the question:

Can I use 'Tie::File' to generate the Hash (which makes this scalable to work with large files and small memory), should I work in memory, or is there some other Perl feature which will make this so easy that I will be embarrased that I asked the question.

TIA

LGC

Nothing succeeds like a budgie with no teeth.

In reply to Tie::File to create a Hash? by LittleGreyCat

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