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
++++++++++++++++++++++++
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}" >> ${file}
echo "${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 ~]$ head -n1 /etc/passwd /etc/hosts /fakefile > head.out 2>>head.err
[oracle@kolkata02 ~]$ head -n1 /etc/passwd /etc/hosts /fakefile > head.out 2>>head.err
[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
head: cannot open ‘/fakefile’ for reading: No such file or directory
head: cannot open ‘/fakefile’ for reading: No such file or directory
head: cannot open ‘/fakefile’ for reading: No such file or directory
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
do
#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
========================================================
