Get Date of Yesterday

----------------------------Ksh Shell Script--------------------------------

#! /usr/bin/ksh
# Get yesterday's date in YYYY-MM-DD format.
# With argument N in range 1..28 gets date N days before.
# Tapani Tarvainen January 2002
# This code is in the public domain.

OFFSET=${1:-1}

case $OFFSET in
  *[!0-9]* | ???* | 3? | 29) print -u2 "Invalid input" ; exit 1;;
esac

eval `date "+day=%d; month=%m; year=%Y`
typeset -Z2 day month
typeset -Z4 year

# Subtract offset from day, if it goes below one use 'cal'
# to determine the number of days in the previous month.
day=$((day - OFFSET))
if (( day <= 0 )) ;then
  month=$((month - 1))
  if (( month == 0 )) ;then
    year=$((year - 1))
    month=12
  fi
  set -A days `cal $month $year`
  xday=${days[$(( ${#days[*]}-1 ))]}
  day=$((xday + day))
fi

print $year-$month-$day
print $month/$day/${year#??}


------------------------Bash Shell Script------------------------------

#!/bin/bash

OFFSET=1;

eval `date "+day=%d; month=%m; year=%Y"`

# Subtract offset from day, if it goes below one use 'cal'

# to determine the number of days in the previous month.

day=`expr $day - $OFFSET`

if [ $day -le 0 ] ;then

month=`expr $month - 1`

if [ $month -eq 0 ] ;then

year=`expr $year - 1`

month=12

fi

set `cal $month $year`

xday=${$#}

day=`expr $xday + $day`

fi

echo $year-$month-$day


------------------------- Linux--------------------------

curdate=`date +%y%m%d -d "yesterday"`

Write Script with arithmetic Operations

#!/bin/sh
echo "enter two numbers"
read a b
c=$(($a+$b))
echo "$a + $b = $c"
# or
let c="$a+$b"
# or
c=`expr $a + 1`

echo "$a + $b is $c"
 

Useful monitoring command of Unix/Linux Vol.2

Change ownership of a directory: chown -Rv username somedir
Change usergroup or a directory: chgrp -Rv usergroup somedir
To set environment variable: setenv
To load the control file: source <filename> (Shell csh only)
To enable sqlplus/Oracle at the first run:

setenv ORACLE_HOME /opt/app/oracle/product/10.2.0/Db_1
setenv ORACLE_SID ASMDB003
setenv ORACLE_TRACE T
setenv ORAENV_ASK NO
setenv NLS_LANG American_America.we8iso8859p1

setenv LD_LIBRARY_PATH /usr/lib:/usr/ucblib:/usr/local/lib:/opt/SUNWspro/lib:$OR
ACLE_HOME/lib:$ORACLE_HOME/precomp/lib:$ORACLE_HOME/rdbms/lib:$ORACLE_HOME/jdbc/
lib:$ORACLE_HOME/dbjava/lib:/user/sfw/lib

setenv PATH /bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:/usr/cc
s/bin:/opt/SUNWspro/bin:${ORACLE_HOME}/bin
setenv PATH ${PATH}:${HOME}/bin

Useful monitoring command of Unix/Linux Vol.1

For Solaris Only:

check number of core: prtdiag -v 
create new user: useradd jsmith
get user information: finger jsmith
set password: passwd jsmith
set default home directory: usermod -d /path/to/new/homedir/ username
set default Shell: change permenently the SHELL at etc/passwd
check Solaris release: cat /etc/release
Check current shell: echo $SHELL
Check shell version: /bin/bash --version