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Mario Domgörgen
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dategrep - print lines matching a date range


  dategrep --start "12:00" --end "12:15" --format "%b %d %H:%M:%S" syslog
  dategrep --end "12:15" --format "%b %d %H:%M:%S" syslog
  dategrep --last-minutes 5 --format "%b %d %H:%M:%S" syslog
  dategrep --last-minutes 5 --format rsyslog syslog
  cat syslog | dategrep --end "12:15"


Do you even remember how often in your life you needed to find lines in a log file falling in a date range? And how often you build brittle regexs in grep to match entries spanning over a hour change?

dategrep hopes to solve this problem once and for all.

If dategrep works on a normal file, it can do a binary search to find the first and last line to print pretty efficiently. dategrep can also read from stdin and compressed files, but as it can't do any seeking in those files, we have to parse every line until we find the first falling in our date range. But at least we don't have to wait for the pipe to be closed. As soon as we find the first date not in the range, dategrep terminates.


But just let me show you a few examples.

The only parameter dategrep really needs is format to tell it how to reckognize a timestamp. In this case dategrep matches all lines from epoch to the time dategrep started. In this case it's just a glorified cat that knows when to stop.

  dategrep --format "%b %d %H:%M:%S" syslog

Besides the format specifiers, which are very similar to the ones used by strptime, dategrep knows about a few named formats like rsyslog or apache.

  dategrep --format apache access.log

But things start to get interesting if you add the start and end options.

  dategrep --start 12:00 --end 12:15 --format rsyslog syslog

If you leave one out it again either defaults to epoch or now.

  dategrep --end 12:15 --format rsyslog syslog

If your like me, you often need to call dategrep from cron and need to get all lines from the last five minutes. So there's an easy shortcut for that.

  dategrep --last-minutes 5 --format rsyslog syslog

Pipes or zipped files can also be handled, but those will be slower to filter. It's often more efficient to just search on an unzipped file or redirect the lines from the pipe to file first. But nothing is stopping you to just call dategrep directly.

  cat syslog | dategrep --end 12:15
  dategrep --end 12:15 syslog.gz


--start|--from DATESPEC

Print all lines from DATESPEC inclusively. Defaults to Jan 1, 1970 00:00:00 GMT. See VALID-DATE-FORMATS for a list of possible formats for DATESPEC.

Additional it's possible to express offsets against dates by using the special syntax $delta from $date, for example

  --from "1 hour ago from -17:00" --to "-17:00"

would search entries from 16:17 to 17:17 if we had now 17:30.

--end|--to DATESPEC

Print all lines until DATESPEC exclusively. Default to the current time. See --start for a list of possible formats for DATESPEC.

--last-minutes MINUTES

Print all lines from MINUTES minutes ago until the beginning of the current minute. So if we have 19:25:43 and MINUTES is five, dategrep will print all lines from 19:20:00 to 19:24:59.

--format FORMAT

Defines a strftime-based FORMAT that is used to parse the input lines for a date. The first date found on a line is used. The list of possible escape sequences can be found under PRINTF DIRECTIVES.

This is a required parameter. Alternatively you can supply the format via the environment variable DATEGREP_DEFAULT_FORMAT.

Additionally, dategrep supports named formats:

  • rsyslog "%b %e %H:%M:%S"

  • apache "%d/%b/%Y:%T %z"

  • iso8601 "%O%Z"


Print all lines between the start and end line even if they are not timestamped.


Ignore all lines without timestamp. Disables --multiline.

--blocksize SIZE

SIZE of the intervals used in the binary search. Defaults to the native blocksize of the file's filesystem or 8129.


Print lines sorted by timestamp even if the timestamps in the input files are overlapping.


Sort files in the order of the first line with a timestamp. For example: If you have a common logrotate configuration, you probably have files like syslog, syslog.1, syslog.2 etc. For dategrep to work we need those files in reverse order: syslog.2, syslog.1, syslog. This options handles that for you.

--configfile FILE

Reads configuration from FILE instead of ~/.dategreprc.


Shows a short help message


Shows the complete man page in your pager.


On startup dategrep reads a configuration file from $HOME/.dategreprc or the file specified by --configfile.

The file consists of sections and variables. A section begins with the name of the section in square brackets and continues until the next section begins. Section names are not case sensitive. Empty lines and lines with comments are skipped. Comments are started with a hash character. dategrep recognizes only one sections: Under formats you can list additional named formats.


  time = %H:%M:%S



Default for the --format parameter. The syntax is described there.


dategrep has only minimal support for compressed files. If any file in ARGV has an extension like .z,.gz,.bz2,.bz, dategrep will call zcat or bzcat respectively and read from it like from stdin.


dategrep expects the files to be sorted. If the timestamps are not ascending, dategrep might be exiting before the last line in its date range is printed.

Compressed files are just piped into dategrep via bzcat or zcat.




It is possible to install this script via perl normal install routines.

  perl Makefile.PL && make && make install

Or via CPAN:

  cpan App::dategrep

You can also install one of the two prebuild versions, which already include all or some of dategrep's dependencies. Which to choose mainly depends on how hard it is for you to install Date::Manip. The small version is just 22.3KB big and includes all libraries except Date::Manip. The big one packs everything in a nice, neat package for you, but will cost you almost 10MB of disk space. Both are always included in the latest release.

So, to install the big version you could just type:

  wget https://github.com/mdom/dategrep/releases/download/$release/dategrep-standalone-big
  cp dategrep-standalone-big.pl ~/bin/dategrep
  chmod +x ~/bin/dategrep

And for the small one (with the apt-get for Debian):

  wget https://github.com/mdom/dategrep/releases/download/$release/dategrep-standalone-small
  cp dategrep-standalone-small.pl ~/bin/dategrep
  chmod +x ~/bin/dategrep
  apt-get install libdate-manip-perl


Copyright 2014 Mario Domgoergen <mario@domgoergen.com>

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see <http://www.gnu.org/licenses/>.