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Re: [nmh-workers] for me a useful script

From: Valdis Klētnieks
Subject: Re: [nmh-workers] for me a useful script
Date: Thu, 23 May 2019 14:20:57 -0400

On Thu, 23 May 2019 13:45:02 -0400, Jude DaShiell said:

> echo "first available message:"
> scan -width 6|head -1

scan -width 6 first     will be much faster.

> echo "last available message:"
> scan -width 6|tail -1

scan -width 6 last  will be much faster.

If you have 10,000 entries in a folder, scan first/last still has to read and
sort the directory, but it can find first and last without opening a file.

A quick test:

[~] strace -f scan -width 6 +inbox 2>| /tmp/inbox | head -1
[~] grep open /tmp/inbox | tail -1
openat(AT_FDCWD, "1171", O_RDONLY)      = 3

Yes, it reads that many files before the back-pressure SIGPIPE from 'head -1'
exiting catches up with it.

scan | tail will have to open and read all 10,000 files.....

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