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Build Status (Linux & macOS) FreeBSD Build Status (FreeBSD)

Shell script to filter logfiles for today's date in an Artificial Ignorance-compatible way

filter-other-days is careful to only throw away entries that we're sure aren't from today. This is implemented by using grep -v on other dates instead of grep on today's date. The rationale here is that it's better to receive irrelevant information than it is to miss relevant information.


Get the source, either by git clone or unpacked tarball. Change into the directory and run sudo make install.

make install uses /usr/local as the prefix by default; you may override this with make install PREFIX=/your/custom/prefix.

make uninstall also works as you'd expect.

See the FAQ for information on the difference between the FreeBSD tarballs and the pristine tarballs.


filter-other-days has four arguments besides --help and --version. -d <seconds> can be used to override the day filter-other-days uses as "today", specified in seconds since the epoch (although -d is not available on every platform; see "What are the system requirements?" below). -l <locales> can be used to load additional locales for filtering besides the system locale ($LANG in the environment) and the C locale. -L is like -l except that it replaces the default list instead of appending to it, and -a can be used to load all system locales but is very slow. See the FAQ for more information on locale support.

filter-other-days accepts input on stdin only.

Note that filter-other-days computes today's date at startup. If the time rolls over to a new day during execution, this will not be accounted for.




What are the system requirements?

This program is designed to require only a POSIX environment for its core functionality. GNU seq was required until version 1.1.0, but this has been fixed.

The -d option does not work under POSIX because it is impossible to implement without extensions. It is available on systems with GNU date -d or BSD date -r semantics; these are feature-tested at runtime. You can determine whether -d is available by examining the help output - it will not be shown if you can't use it. The -l, -L and -a options suffer from identical requirements and thus have identical feature-testing behavior.

That all being said, this program was tested on systems that include extensions to POSIX, so there may be lingering dependencies on these extensions. If you find any such dependencies, they will be considered bugs. Please report these in the bug tracker.

If you want to run the test suite, you also need Bash and either faketime or a system where -d is available.

How does the localization support work?

filter-other-days is able to extract information from the locales installed on the system and use this information for filtering. By default, it will load the C locale and the system default locale, as defined by $LANG in the environment. You can add to this list with the -l option or replace this list with the -L option.

filter-other-days does not automatically load all available locales because this operation is extremely slow (it is on the order of seconds, sometimes tens of seconds), but if you really want to do this you can pass -a. -l and -L cannot be used at the same time as -a.

What's with the "FreeBSD" release tarballs?

I discovered a bug in FreeBSD's POSIX support that prevented filter-other-days' localization support from working. It later turned out that NetBSD is also affected by this same bug.

The FreeBSD tarballs contain a version of filter-other-days that has been patched to work around this problem. You need it on FreeBSD 12 and below, and current versions of NetBSD - NetBSD 8.1, as of this writing. FreeBSD 12.1 fixes this bug so you do not need the patched version.

When all operating system versions with this bug are obsoleted by their developers, the filter-other-days FreeBSD release tarballs will be dropped.

What systems has filter-other-days successfully been tested on?

filter-other-days with the -d option has successfully been tested on the following systems:

  • GNU/Linux
  • FreeBSD 12.1-RELEASE
  • Cygwin
  • OpenIndiana Hipster 20191106
  • OmniOSce r151032

filter-other-days with FreeBSD patches has successfully been tested on the following systems:

  • GNU/Linux
  • FreeBSD 11.3-RELEASE
  • FreeBSD 12.0-RELEASE
  • FreeBSD 12.1-RELEASE
  • NetBSD 8.1
  • Cygwin

filter-other-days does NOT run on the following systems because they do not conform to POSIX:

  • OpenBSD 6.3 and 6.6

filter-other-days has not been tested on any systems where -d is unavailable because I was unable to find any other freely available, widely used Unix systems that were significantly different from those on this list. If you successfully test filter-other-days on a new system with or without -d, please report back your findings.

I'm passing a file but it says "unrecognized option 'filename'".

Unlike many Unix programs, filter-other-days does not accept files on the commandline. This is because it makes the argument parsing code more complicated and your shell can accomplish the same thing just as well:

$ filter-other-days < filename

Besides, usually you'd want to use cat on multiple files before piping to filter-other-days anyway.

How can I filter output from systemd's journal?

Use journalctl --output=short. That will output journal entries one per line, with a date format filter-other-days supports.

I'm seeing entries from other days!

filter-other-days is intentionally designed to only filter out what it already knows about. This is because it is dangerous to throw away information you don't understand. This point is particularly salient when one is considering implementing an Artificial Ignorance system based on filter-other-days.

That being said, it's obviously unideal that filter-other-days is not doing its job. Please file a bug and be sure to include some sample input and any interesting variations. When in doubt, include more. Your samples will be added to the test suite and additional filtering will be added to make those tests pass.


Affero GPL 3.0 or later


AJ Jordan