Facing problem with Alias created through script.

Shell Programming and Scripting
1

Hi Guru's,

I am creating alias for db instance running on a server through script, am able to create them based on /etc/oratab entries and can use successfully with the below script.

#!/bin/bash

SCRIPT_PATH=${HOME}/scripts/db/script
LOG_FILE=${HOME}/scripts/db/log/database_instances_alias.log
CONN_DATABASE='sqlplus -s / as sysdba'
DB_INSTANCES=$(cat /etc/oratab | egrep -v '^#|^$' | grep -v '^+'|cut -d":" -f1,2)
sed -n '1,8p' ${HOME}/.bashrc > ${HOME}/.bashrc_bkp
echo " " >>${HOME}/.bashrc_bkp
printf "%s%20s%20s%20s%20s\n" "S.No" "DATABASENAME"  "ORACLE_HOME"  "DB_STATUS" "DB_MODE" > ${LOG_FILE}
SERIAL=0
for SINGLE_INSTANCE in ${DB_INSTANCES[@]}
do
##DATABASE NAMES
DATABASE_NAME=$(echo $SINGLE_INSTANCE | awk -F ":" '{print $1}')
##ORACLE HOME
DATABASE_HOME=$(echo $SINGLE_INSTANCE | awk -F ":" '{print $2}')
ps -ef | grep pmon | grep -q $DATABASE_NAME
  if [ $? -eq 0 ]; then
    DB_STATUS="UP"
    export ORACLE_SID=$DATABASE_NAME
    export ORACLE_HOME=$DATABASE_HOME
    DATABASE_MODE=$(echo "select open_mode from v\$database;" | $CONN_DATABASE | sed -n '4p')
       case $DATABASE_MODE in
             'MOUNT')
                                DATABASE_MODE_S=${DATABASE_MODE}
             ;;
             'READ WRITE')
                                DATABASE_MODE_S=${DATABASE_MODE}
             ;;
             'READ ONLY')
                                DATABASE_MODE_S=${DATABASE_MODE}
             ;;
             'NOMOUNT')
                                DATABASE_MODE_S='Instance Running Not Mounted'
             ;;
             *)
                                DATABASE_MODE_S='N/A'
             ;;
       esac

  else
    DB_STATUS="DOWN"
    DATABASE_MODE_S="N/A"
  fi
SERIAL=$(expr $SERIAL + 1)
printf "%s%20s%25s%15s%20s\n" "$SERIAL" "$DATABASE_NAME"  "$DATABASE_HOME"  "$DB_STATUS" "$DATABASE_MODE_S" >> ${LOG_FILE}
echo "alias $SERIAL='export ORACLE_SID="$DATABASE_NAME";export ORACLE_HOME="$DATABASE_HOME";PS1=\"[\\u\\h ] $DATABASE_NAME \$\"'" >> ${HOME}/.bashrc_bkp
echo "alias showdb='$SCRIPT_PATH/database_instances_alias_bkp.sh;cat $LOG_FILE;. $HOME/.bashrc'" >>${HOME}/.bashrc_bkp
done
mv -f $HOME/.bashrc_bkp $HOME/.bashrc
. $HOME/.bashrc

But i am facing problem when the number of entries changed
like
suppose there are 8 entries in oratab and the script will create 8 aliasis, if i delete 2 entries from oratab so script will create alias for 6 entries only, but am not able to unalias 7 and 8. so how can i unalias them

someone please help

Regard's
Venkat

2

If you know the alias count upfront, why don't you

for i in {1..8}; do unalias $i; done

as the first statement in the script?

3

Hi,

Thanks for the response RudiC,

yes, may someone have better idea around
when am checking length of an array it displays 1
echo ${DB_INSTANCES[*]}
so am following echo ${DB_INSTANCES[*]}|wc -l
is this a correct way to follow.

please help

Regard's
Venkat

---------- Post updated at 06:37 PM ---------- Previous update was at 05:15 PM ----------

Hi All,

Thank you RudiC driving me

I resolved my issue with snippet below

diff $HOME/.bashrc $HOME/temp_alias_compare_file >/dev/null 2>&1
  if [ $? -eq 1 ];then
    diff $HOME/.bashrc $HOME/temp_alias_compare_file | grep 'alias' | grep -v 'showdb' | while read line
         do
            unalias $(echo $line | awk -F"=" '{print $1}' | awk -F"alias" '{print $2}' | sed 's/^ //g')
         done
  fi
. $HOME/.bashrc

Regard's
Venkat

4

Please use code tags as required by forum rules!

As you are using awk anyhow in your solution, why not make the entire action an awk script?
Two thoughts:

  • when creating the aliases in the .bashrc script, why not add the respective unalias es in parallel?
  • as you are using bash , try unalias {1..20} and just accept/ignore the not found errors...
1 Like