OracleDBAtalk: Shell Scripting

Shell Scripting Handy

User creation at OS level (usercreate_os.sh)

#!/bin/bash

#this script creates an account on the local system.

#you will be prompter for the account name and password

#Ask for username

read -p 'Enter the username: ' USER_NAME

#Ask for the real name

read -p 'Enter the name of the person who is this account for: ' COMMENT

#ask for the password

read -p 'Enter the password to use for the account: ' PASSWORD

#create the username

useradd -c "${COMMENT}" -m ${USER_NAME}

#set the password for the username

echo ${PASSWORD} | passwd --stdin ${USER_NAME}

#force password change on first login

passwd -e ${USER_NAME}

######################################################################

Script2:

RANDOM Each time this parameter is referenced, a random integer between 0 and 32767

is generated. The sequence of random numbers may be initialized by assign‐

ing a value to RANDOM. If RANDOM is unset, it loses its special properties,

even if it is subsequently reset.

[oracle@kolkata02 ~]$ echo ${RANDOM}

24092

[oracle@kolkata02 ~]$ echo ${RANDOM}

1748

[oracle@kolkata02 ~]$ echo ${RANDOM}

2398

[oracle@kolkata02 ~]$ !v ----> this will opens the last closed file

#!/bin/bash

#This scripts generates a list of random passwords

#A random number as a password

PASSWORD=${RANDOM}

echo "${PASSWORD}"

#Three random numbers together

PASSWORD="${RANDOM}${RANDOM}${RANDOM}"

echo "${PASSWORD}"

#use the current date/time as the basis for the password

PASSWORD=$(date +%s) ---->'+' is for format and %s is for seconds since 1970 UTC

echo "${PASSWORD}"

#use nano seconds to act as randomization

PASSWORD=$(date +%s%N) --->%N is the nano seconds

echo "${PASSWORD}"

# A better password

PASSWORD=$(date +s%N | sha256sum | head -c32)

echo "${PASSWORD}"

# An even better passsword

PASSWORD=$(date +s%N${RANDOME}${RANDOM} | sha256sum | head -c32)

echo "${PASSWORD}"

# An even better passsword

Special_character=$(echo '!@#$%^&*()_+' | fold -w1 | shuf | head -c1)

echo "${PASSWORD}${Special_character}" --->here special character will be appended

++++++++++++++++++++++++

[oracle@kolkata02 ~]$ echo "1" >> cheksumdata.txt ---->this will append the data in the next line

[oracle@kolkata02 ~]$ vi cheksumdata.txt

[oracle@kolkata02 ~]$ echo "2" >> cheksumdata.txt ---->this will append the data in the next line

[oracle@kolkata02 ~]$ vi cheksumdata.txt

asdfdsdfasdf34343434

++++++++++++++++++++++++

head -2 /etc/passwd

head -n1 /etc/passwd

head -n -1 /etc/passwd

head -c1 /etc/passwd

head -c2 /etc/passwd

echo "testing" | head -c2

date +%s%N | sha256sum | head -c32

++++++++++++++++++++++++

Parameter is the variable using inside the shell script

Argument is the value passing to the parameter

${0} ---> is the positional parameter, which takes filename itself

[oracle@kolkata02 ~]$ which head ---->which -a head

/usr/bin/head

${#} ---> it tells number of arguments you passed to the script

${@} ---> this will be used in for loop and we dont know how many user input will be passed as arguments

${*} ---> This is consider/combine all the user inputs/arguments into a single argument

[oracle@kolkata02 ~]$ for username in zameer naseer ayaan

> do

> echo hi ${username}

> done

hi zameer

hi naseer

hi ayaan

[oracle@kolkata02 ~]$

#!/bin/bash

echo 'you executed this command: '${0}

true

sleep

shift

while loop

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

#This script demonstrates I/O redirection

#standard input

#standard output

#standard error

#redirect STDOUT to a file

file="/tmp/data"

head -n1 /etc/passwd > ${file}

#redirect STDIN to a program

read LINE < ${file}

echo "the line contains : ${file}"

#we can change the password of the user by redirecting the output from password file to passwd

[oracle@kolkata02 ~]$ echo "secret" > password

[oracle@kolkata02 ~]$ cat password

secret

[root@kolkata02 oracle]# sudo passwd --stdin testuser1 < password

Changing password for user testuser1.

passwd: all authentication tokens updated successfully.

# ">" overwrite the existing content in a file

head -n3 /etc/passwd > ${file}

echo contents of the file ${file} is:

cat ${file}

#redirect STDOUT to a file, appending to the file

echo "${RANDOM} ${RANDOM}" >> ${file}

echo

echo "contents of the file: ${file}"

cat ${file}

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

[oracle@kolkata02 ~]$ read x < /etc/redhat-release

[oracle@kolkata02 ~]$ echo ${x}

Red Hat Enterprise Linux Server release 7.9 (Maipo)

[oracle@kolkata02 ~]$ read x 0< /etc/redhat-release

[oracle@kolkata02 ~]$ echo ${x}

Red Hat Enterprise Linux Server release 7.9 (Maipo)

[oracle@kolkata02 ~]$

[oracle@kolkata02 ~]$ head -n1 /etc/passwd /etc/hosts /fakefile > head.out --->this will not redirect the error to the file head.out

head: cannot open ‘/fakefile’ for reading: No such file or directory

[oracle@kolkata02 ~]$ cat head.out

==> /etc/passwd <==

root:x:0:0:root:/root:/bin/bash

==> /etc/hosts <==

127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4

[oracle@kolkata02 ~]$

[oracle@kolkata02 ~]$ head -n1 /etc/passwd /etc/hosts /fakefile > head.out 2>head.err ---> this will write the error into the file head.err

[oracle@kolkata02 ~]$ cat head.err

head: cannot open ‘/fakefile’ for reading: No such file or directory

the below 2>>head.err will append the error

[oracle@kolkata02 ~]$ head -n1 /etc/passwd /etc/hosts /fakefile > head.out 2>>head.err

[oracle@kolkata02 ~]$ cat head.err

head: cannot open ‘/fakefile’ for reading: No such file or directory

[oracle@kolkata02 ~]$

What if we wanted to send the standard output and standard error to the same file, we will see the old syntax and new syntax for that

[oracle@kolkata02 ~]$ head -n1 /etc/passwd /etc/hosts /fakefile > head.both 2>&1

[oracle@kolkata02 ~]$ cat head.both

==> /etc/passwd <==

root:x:0:0:root:/root:/bin/bash

==> /etc/hosts <==

127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4

head: cannot open ‘/fakefile’ for reading: No such file or directory

[oracle@kolkata02 ~]$

The new syntax for the same above operation is as below

[oracle@kolkata02 ~]$ head -n1 /etc/passwd /etc/hosts /fakefile &> head.both

[oracle@kolkata02 ~]$ cat head.both

==> /etc/passwd <==

root:x:0:0:root:/root:/bin/bash

==> /etc/hosts <==

127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4

head: cannot open ‘/fakefile’ for reading: No such file or directory

[oracle@kolkata02 ~]$

&>> ---> will append the output

===============Below is to display the abended process logs================

#!/bin/bash

BASE_DIR=/u01/app/oracle/scripts

log_dir=$BASE_DIR/log_dir

gg_processes=$BASE_DIR/log_dir/gg_processes.log

gg_process_Detail=$BASE_DIR/gg_process_Detail.txt

Abended_ggprocess=$BASE_DIR/Abended_ggprocess.txt

gg_process_log_output=$BASE_DIR/gg_process_log_output.txt

rm ${gg_process_log_output}

echo $ORACLE_HOME

echo $GG_HOME

cd $GG_HOME

pwd

$GG_HOME/ggsci <<EOF > ${gg_processes}

info all

exit

EOF

cat ${gg_processes} | grep ABENDED | awk '{ print $3 }' > ${Abended_ggprocess}

while read line

#echo -e "\n"

#echo -e "The below is the output of last four lines of ${line} GG Process log, please check\n" >>${gg_process_log_output}

echo -e "The below is the output of last four lines of `echo -e "\e[1;31m ${line} \e[0m"` GG Process log, please check\n" >>${gg_process_log_output}

tail -4 /u01/app/oracle/product/ogg/dirrpt/${line}.rpt >> ${gg_process_log_output}

echo -e "\n" >> ${gg_process_log_output}

done <${BASE_DIR}/Abended_ggprocess.txt

========================================================

OracleDBAtalk

Monday, August 23, 2021

Shell Scripting

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