Count backwards with seq in Linux

Written by - 0 comments

Published on - Listed in Linux


Needed to manually create some basic web statistics using awstats (a one shot statistic). My approach was to get all the rotated logs and create one big access log. I wanted the lines of that access log in the correct order to avoid awstats tumbling.

First I unzipped all rotated logs:

gunzip *gz

Then I needed to get the log entries from rotated file 40 down to rotated file 9. But here's the catch: How do I count down without having to note every single number from 40 to 9 (that would be something like for i in 40 39 38 37, etc)? I know how to automatically count up using seq:

$ seq 1 5
1
2
3
4
5

So I needed to find a way to count backwards. The solution? seq again :-)

seq offers an optional parameter between the starting and the ending number. From the --help output:

$ seq --help
Usage: seq [OPTION]... LAST
  or:  seq [OPTION]... FIRST LAST
  or:  seq [OPTION]... FIRST INCREMENT LAST
Print numbers from FIRST to LAST, in steps of INCREMENT.
[...]

Example: Count up to 10 but increase with 2 numbers:

$ seq 1 2 10
1
3
5
7
9

The INCREMENT number can be negative, too:

$ seq 10 -1 1
10
9
8
7
6
5
4
3
2
1

And this is actually the way to count down. To put together all rotated logs in the correct order, I finally used the following command:

$ for i in $(seq 40 -1 9); do cat access.log.$i >> final.access.log; done


Add a comment

Show form to leave a comment

Comments (newest first)

No comments yet.

RSS feed

Blog Tags:

  AWS   Android   Ansible   Apache   Apple   Atlassian   BSD   Backup   Bash   Bluecoat   CMS   Chef   Cloud   Coding   Consul   Containers   CouchDB   DB   DNS   Database   Databases   Docker   ELK   Elasticsearch   Filebeat   FreeBSD   Galera   Git   GlusterFS   Grafana   Graphics   HAProxy   HTML   Hacks   Hardware   Icinga   Influx   Internet   Java   KVM   Kibana   Kodi   Kubernetes   LVM   LXC   Linux   Logstash   Mac   Macintosh   Mail   MariaDB   Minio   MongoDB   Monitoring   Multimedia   MySQL   NFS   Nagios   Network   Nginx   OSSEC   OTRS   Office   PGSQL   PHP   Perl   Personal   PostgreSQL   Postgres   PowerDNS   Proxmox   Proxy   Python   Rancher   Rant   Redis   Roundcube   SSL   Samba   Seafile   Security   Shell   SmartOS   Solaris   Surveillance   Systemd   TLS   Tomcat   Ubuntu   Unix   VMWare   VMware   Varnish   Virtualization   Windows   Wireless   Wordpress   Wyse   ZFS   Zoneminder