Can ugrep.exe search files that another process on Windows has open for writing?

[hollymcr]

I have an application which writes log files whilst it runs.

I can search those files using (GNU) grep.exe whilst the app is still running but ugrep just reports "No such file or directory".

These files are large (1GB+) so I'd really prefer to use ugrep over grep. Also there is an option to generate them as gzip compressed files which saves loads of diskspace but grep can't handle them (and I haven't found a good zgrep for Windows - that search is what led me to ugrep).

Have used ag.exe in the past but really looking for something that is commandline compatible with grep as far as possible since I spend most of my time on Linux.

[genivia-inc]

Thank you for your feedback.

Read/write clashes between processes as not uncommon on Windows, whereas Unix/Linux it's never an issue.

I believe a small change to the Windows CreateFileW call in ugrep.exe should resolve this. Basically when opening a file for reading with CreateFileW:

CreateFileW(wfilename, GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_EXISTING, FILE_FLAG_SEQUENTIAL_SCAN, NULL)

should also allow FILE_SHARE_WRITE:

CreateFileW(wfilename, GENERIC_READ, FILE_SHARE_READ | FILE_SHARE_WRITE, NULL, OPEN_EXISTING, FILE_FLAG_SEQUENTIAL_SCAN, NULL)

I'll verify this and fold it into the next release.

[genivia-inc]

I've made a tiny update and recompiled the ugrep.exe v7.3 files located in the repo bin dirs: https://github.com/Genivia/ugrep/tree/master/bin/win64

Tested as follows in cmd.exe:

C:\Users\[...]> copy con testcon.txt
test
this
out

then leave that open and start new cmd.exe to search with ugrep.exe test testcon.txt which returns test.

So this should work. If an error occurs, then it the other process prevents the file from being read when it writes it, or it deleted the file, or other manipulations prevents read access.

[hollymcr]

That's fantastic, I can confirm this works as intended in my brief testing.