I'm trying to use simple commands to extract data from a log file.

Here's a sample line from the file - - [23/Mar/2008:00:03:10 +0000] "GET /javascript/email.js HTTP/1.1" 200 359 "http://www.cs.ucd.ie/Staff/AcademicStaff/bsmyth/"; "Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv: Gecko/20080201 Firefox/"

How can I get the date and time of the first and last log entry to the file displayed in the following format:


with no other characters?


Try this to get the timestamps from the first and last lines in your log file:

{ head -n 1 my_log_file; tail -n 1 my_log_file; } | awk '{print $4}' | tr -d '['

As an aside, this looks like an Apache log, and you may wish to look into using Logstash to parse your structured logs.

  • 1
    Nice, but you might replace the head; tail bit with sed -n '1p;$p' for greater simplicity and speed. It will only open the file once instead of twice, and doesn't need shell braces to combine commands. – Wildcard Nov 15 '16 at 7:21
  • 1
    @Wildcard: it only runs one process, but it reads the whole file whereas tail seeks to the last block-or-so; this is faster if the logfile is very large, and logfiles sometimes are very large, especially the ones you need to look at when there's a problem. – dave_thompson_085 Nov 15 '16 at 10:17
awk -F"[][]" 'NR==1{sub(" .*","",$2);print $2}END{sub(" .*","",$2);print $2}' logfile

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