All these years I was using *all dirty shell script hacks* to create my own date manipulation utilities for backups and other admin task. Thanks to this project no more dirty work.

Recently our site visitor Milton left a comment about this nice utility. This utility is very good if you would like to do lots of date manipulation or to crate report/log file names with date in filename.

From the project home page:
yest is a command line date/time manipulation and formatting program, very useful in scripts. You can easily add or subtract days, hours and/or minutes from a specified date. It supports all date command output formats plus more.

This program is called “yest” because the default is to output yesterday’s date. This utility knows about leap year, aylight savings time, and such variations.

Task: Install yest

Download yest from project home page. Or use wget command as follows:
$ cd /tmp
$ wget http://easynews.dl.sourceforge.net/sourceforge/yest/yest-2.7.0.3.tgz

Untar the source code:
$ tar -zxvf yest-2.7.0.3.tgz

Compile and install binary
$ su -
# gcc -o /usr/bin/yest yest-2.7.0.3.c

Install man page:
# cp yest-2.7.0.3.man1 yest.1
# gzip yest.1
# cp yest.1.gz /usr/share/man/man1/


How do I use yest?

Following command will display yesterdays date (default):
$ date
Thu Oct 12 23:45:24 IST 2006
$ yest
10/11/2006

Display the date ten days ago (-10 or +10 next 10 days)
$ date
Thu Oct 12 23:46:23 IST 2006

$ yest -10
10/02/2006

$ yest +10
10/22/2006

Format date in dd-mm-yyyy:
$ yest -10 "%d-%m-%Y"
02-10-2006

Get more help
$ yest --help
$ man yest


yest in action

So to executing a script/command on the last day of a month, I was using following script:
#! /bin/bash
TOM=$(TZ=MST-24 date +%d)
if [ $TOM -eq 1 ]; then
# commands or script on the last day of a month
/path/to/mytask
fi

But with yest it is just one line shell script 😀
[ $(yest +0 "%d") -eq $(yest "%L") ] && /path/to/mytask || :

=> yest Download is highly recommended tool for all seasoned UNIX admin.