Shell Script Which Gets Executed With Greetings – The Moment User Logs In

in Categories Time and Date last updated April 5, 2008

Write shell script which gets executed the moment user logs in, it should greet user

Script first finds out current hour using date command

Depend upon time of the day, it will say Good morning or Good afternoon to user.

Open your bash / shell startup file i.e. profile file – ~/.bash_profile and put path to this script in file as follow:
/home/you/path/to/script

Sample shell script to greet user

#!/bin/bash
# Shell program which gets executed the moment the user logs in, it should
# display the message "Good morning", "Good Afternoon", or "Good Evening"
# depnding upon the time which the user logs in.
# =====================================================================
# Q. How to run this script as soon as user logs in?
# A. Open your bash startup file aka profile file - ~/.bash_profile
# and put path to this script in file as follow:
# . /path/to/greetings.sh
# -----------------------------------------------
# Copyright (c) 2005 nixCraft project <http://cyberciti.biz/fb/>
# This script is licensed under GNU GPL version 2.0 or above
# -------------------------------------------------------------------------
# This script is part of nixCraft shell script collection (NSSC)
# Visit http://bash.cyberciti.biz/ for more information.
# -------------------------------------------------------------------------
 
# get current hour (24 clock format i.e. 0-23)
hour=$(date +"%H")
 
# if it is midnight to midafternoon will say G'morning
if [ $hour -ge 0 -a $hour -lt 12 ]
then
  greet="Good Morning, $USER"
# if it is midafternoon to evening ( before 6 pm) will say G'noon
elif [ $hour -ge 12 -a $hour -lt 18 ] 
then
  greet="Good Afternoon, $USER"
else # it is good evening till midnight
  greet="Good evening, $USER"
fi
 
# display greet
echo $greet

Shell Script to read any year and find whether it is a leap year or not

in Categories Time and Date last updated April 5, 2008

A leap year comes once every four years. It is the year when an extra day is added to the Gregorian calendar used by most of the world.

An ordinary year has 365 days. A leap year has 366 days. The extra day is added to the month of February. In an ordinary year, February has 28 days. In a leap year, it has 29 days. This extra day is called a leap day.

How do I find out leap year?

A year is a leap year if it can be evenly divided by four. For example, 1996 was a leap year. But a year is not a leap year if can be evenly divided by 100 and not by 400. This is why 1700, 1800, 1900 were not leap years, but 2000 was.

Shell script to determine if entered year is leap or not…

#!/bin/bash
# Shell program to read any year and find whether leap year or not
# -----------------------------------------------
# Copyright (c) 2005 nixCraft project <http://cyberciti.biz/fb/>
# This script is licensed under GNU GPL version 2.0 or above
# -------------------------------------------------------------------------
# This script is part of nixCraft shell script collection (NSSC)
# Visit http://bash.cyberciti.biz/ for more information.
# -------------------------------------------------------------------------
 
# store year
yy=0
isleap="false"
 
echo -n "Enter year (yyyy) : "
read yy
 
# find out if it is a leap year or not
 
if [ $((yy % 4)) -ne 0 ] ; then
   : #  not a leap year : means do nothing and use old value of isleap
elif [ $((yy % 400)) -eq 0 ] ; then
   # yes, it's a leap year
   isleap="true"
elif [ $((yy % 100)) -eq 0 ] ; then
   : # not a leap year do nothing and use old value of isleap
else
   # it is a leap year
   isleap="true"
fi
if [ "$isleap" == "true" ];
then
   echo "$yy is leap year"
else
   echo "$yy is NOT leap year"
fi

Shell script to read a character (upper or lower), digit, special symbol and display message according to the character entered

in Categories Decision Making last updated April 5, 2008

This script uses sed command to find out all digits or upper characters. -z string (conditional expression) will return true if the length of string is zero.

Script logic

Read one character
[1] Use sed command to determine input character is digit or not (sed -e ‘s/[A-Z]//g’))

[2] Attempt to match regex [0-9] i.e. all digit against the pattern space

[3] If successful, replace that portion matched with replacement // i.e. do nothing.
If digits are in input, it will replace all those digit, and if input is only digit, nothing is left i.e. string is zero and that is what tasted with -z conditional expression.

#!/bin/bash
# Shell script to read a character (upper or lower), digit, special symbol and
# display message according to the character entered
# -----------------------------------------------
# Copyright (c) 2005 nixCraft project <http://cyberciti.biz/fb/>
# This script is licensed under GNU GPL version 2.0 or above
# -------------------------------------------------------------------------
# This script is part of nixCraft shell script collection (NSSC)
# Visit http://bash.cyberciti.biz/ for more information.
# -------------------------------------------------------------------------
 
char=""
echo -n "Enter a one character : "
read char
# use sed command to determine input character is digit or not
# -e : start script
# s/[0-9]// : Attempt to match regex [0-9] i.e. all digit against the pattern space (echo $char).
# If  successful,  replace  that  portion  matched  with replacement i.e. // do nothing. 
# g : Global replacement
# so if digit are in input it will replace all those digit, and if input is only digit, nothing
# is left i.e. string is zero and that is what tasted with -z
if [ -z $(echo $char | sed -e 's/[0-9]//g') ]
then
	echo "$char is Number/digit"
elif [ -z $(echo $char | sed  -e 's/[A-Z]//g') ] # find out if character is upper
then
        echo "$char is UPPER character"
 
elif [ -z $(echo $char | sed -e 's/[a-z]//g') ] # find out if character is lower
then
        echo "$char is lower character"
else
	echo "$char is Special symbol" # else it is special character
fi

Shell script to read 3 numbers and find the greaters of the three

in Categories Shell Math last updated April 4, 2008
#!/bin/bash
# Shell script to read 3 numbers and find the greaters of the three
# -------------------------------------------------------------------------
# Copyright (c) 2005 nixCraft project <http://cyberciti.biz/fb/>
# This script is licensed under GNU GPL version 2.0 or above
# -------------------------------------------------------------------------
# This script is part of nixCraft shell script collection (NSSC)
# Visit http://bash.cyberciti.biz/ for more information.
# ----------------------------------------------------------------------
echo -n "Please enter three numbers (separate number by space) : "
read a b c
# compare a with b and c. Note -a is logical and operator
if [ $a -gt $b -a $a -gt $c ]
then
   big=$a
elif  [ $b -gt $a -a $b -gt $c ] # compare b with a and c
then
   big=$b
elif  [ $c -gt $a -a $c -gt $b ] # compare c with a and b
then
   big=$c
elif [ $a -eq $b -a $a -eq $c -a $b -eq $c -a $c -eq $b ] # see if all of them are equal or not
then
   big="All three numbers are same (equal)"
else # something must be wrong if we are here, like one of number is character such as 'A'
   big="Can not guess greaters of three numbers"
fi
# display result 
echo "Result : $big"