unix for dba

8/14/2019 Unix for DBA

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Oracle Center of Excellence

Unix For DBA’s

Oracle CoE

TCS - GDC , SEEPZ




Variables we need in .profile

PATH Variable : • set in .profile

• Sequence of directories that the shell will search to look for a command

• The ORACLE_HOME must be added to PATH

ORACLE_SID variable : Must be set in the shell, can be set in .profile or atcommand prompt.Identifies the oracle instance you are currently working on.

$echo ORACLE_SID

This variable will identify the Oracle instance you are currently working in.




Perform Searches in Unix:

grep : Searches for a pattern in a file• grep -i ‘pattern’ filename

find : to search for files on the filesystem

find / -name <filename> -print

Monitoring Background Processes running on Unix

ps : Displays the processes on the system

• ps -ef • ps -ef | grep ora : Shows the oracle background processes running. Can be used

to determine whether an instance is running or not.




Cron (Contd.)

• First Field specifies the no. of minutes after the hour when the command is to beexecuted (legal values 00 to 59)

• Second filed specifies the hour in 24 hour format (1 to 24)

• Third field is day of the month (1 to 31) .The * on this field means it is to beexecuted daily

• Fourth field specifies the month (1-12)

• Fifth field is the day of the week (0-6 Sunday being 0)

A user can add a command to his file by

crontab <commands>




Running a process in the background

sort -o emp.lst emp.lst & - runs the sort as a background process

nohup : will continue running the background process even if the user logsout

nohup sort emp.lst &




Monitoring Disk usage

df : reports free space available on disk df -k : will show all the mount points and their sizes in Kilo Bytes

du : reports the disk usage

compress : compresses file and generates the filename.Z

compress filename : give a compressed file as filename.Z




Backing up operating system files:

dd : Used mainly for copying media like floppy and tapedd if=/dev/rdsk/f0q18t of=temp bs=147456

if=(input filename)

of=(output filename)

bs=(blocksize)

cpio : used to copy files to and from a backup device

ls | cpio -ov >/dev/rmt/0m

ls generates the list of files (find too can be used for this)

-o creates an archive which is to be redirected to the backup device

cpio -iv < /dev/rmt/0m restores the files from backup device




Backing up operating system files (contd.):

tar : creates archives on tapes and floppies. Older cousin of cpiotar cvf /dev/rmt/0m /Oracle/dbs/initTest.ora

tar cvfkb /dev/rmt/0m 1440 18 index.sql : multi-volume backup

tar xvf /dev/rmt/0m

tar uvf /dev/rmt/0m index.sql




What is Mounting ?

Mounting is the process of attaching a filesystem to the root filesystem. The point atwhich a directory/filesystem is attached is called the mount point.

Mount /dev/charlie /oracle :mounts the ‘/dev/charlie’ at mount point ‘/oracle’.

Mount -f HS, lower /dev/cd0 /cdrom

-f is used to specify the type of filesystem to be mounted

HS is the type of CD-ROM format

lower keyword ensures lowercase files are displayed in lowercase only

-r option if used will mount the filesystem in read-only mode

Umount can be used to dismounting the file system, either the filesystem or themount point is the argument. Dismounting/unmounting makes the filesysteminaccessible.

umount /oracle : mount point

umount /dev/charlie : device name of filesystem




How do I change the access rights to a file?

Chmod is used to set the permissions for all three categories of users (owner,group, others)

chmod u+x initTEST.ora : adds(+) executable(x) permission on initTEST.ora toowner(u)

chmod category operation permission filename(s)

category : u(owner), g(group), o(others), a(all, is the default)

permission : r(read), w(write), x(executable)

chmod 764 initTEST.ora : gives rwx(7) to owner, rw(6) to group, r(4) to others

r(read) = 4, w(write) = 2, x(executable) = 1




How do I change the access rights to a file? (contd.)

Chown is used to change the ownership of a file.

Chown oracle initTEST.ora : now oracle is the owner of the file

Chgrp changes the group ownership of the file

chgrp dba initTEST.ora : the group dba has the group ownership of the file, whichmeans all the users belonging to the group dba will have same rights to the file asthe group permissions.




Can I log in as a different user without disconnecting the currentsession?

su -u oracle : will attempt to log you in as user oracle

O l C f E ll




Miscellaneous

rlogin: Unlike telnet does not prompt for username. Logs into remotemachine as the user of the current machine.So entry for this user mustbe in /etc/passwd in remote m/c.

rlogin 192.168.0.2

lpstat : status of the printer lpstat -p pr1 : status of print job on printer pr1

.exrc file : All sets, maps and abbreviations for vi can be stored. At startup

vi looks for the commands in this file.Set ignorecase

/etc/passwd file : Has all the users in the system with their passwords

O l C t f E ll




Miscellaneous (contd.)

Umask : The value of this variable decides the default permissions which a file will

have when created by a user. Is normally declared in .profile.

Umask 000 : will create files with 777 permissions.

ln is used to give files several filenames. Its like a shortcut in Windows.

ln emp.sql employee : now emp.sql can also be accessed as employee.

O l C t f E ll



Shell Programming

Basics


O l C t f E ll




Shell Programming

• when a group of UNIX command to be executed regularly ,then they arestored in a file , such files are called Shell Script , Shell Programs or Shell Procedure

• no restriction on the extension but it is a common practice to use “.sh” extension for shell script program.

O l C t f E ll




Example of Simple Shell Script

• $cat script.sh

# This is a comment line

date # command

cal ̀date “+%m 20%y” ̀ # command echo ‘Calendar for the current month shown above’ # command

• “vi” editor is use to create file and have to make executable by using:

chmod +x filename ( or) chmod 755 filename

• to execute the shell program just have to type the name of the file at thecommand prompt.

O l C t f E ll




read : Making Shell InteractiveThe “read ” statement is shell’s internal tool for taking input from the user.

• $ cat emp1.sh

# Script: emp1.sh – Interactive version

# The pattern and filename is to be supplied by the user

echo “\n Enter the pattern to be searched : \c “

read pname

echo “ Enter the file to be used: \c”

read flname

echo “\n Searching for $pname for file $filename\n”

grep “$pname” $flname

echo “\n Selected record shown above\n” (contd…)

O l C t f E ll




Example of Simple Shell Script

• $cat script.sh

# This is a comment line

date # command

cal ̀date “+%m 20%y” ̀ # command echo ‘Calendar for the current month shown above’ # command

• “vi” editor is use to create file and have to make executable by using:

chmod +x filename ( or) chmod 755 filename

• to execute the shell program just have to type the name of the file at thecommand prompt.





read : Making Shell InteractiveThe “read ” statement is shell’s internal tool for taking input from the user.

• $ cat emp1.sh

# Script: emp1.sh – Interactive version

# The pattern and filename is to be supplied by the user

echo “\n Enter the pattern to be searched : \c “

read pname

echo “ Enter the file to be used: \c”

read flname

echo “\n Searching for $pname for file $filename\n”

grep “$pname” $flname

echo “\n Selected record shown above\n” (contd…)





read : Making Shell Interactive (Contd…)

• The script pauses at two points –

• First ask for pattern to be entered . Inputing the string for ‘ pname’

• And assign its value to ‘ pname’ .

• Next it ask for filename ,entry the string assigns the value for it.





Command Line Arguments:

Positional Parameters

• Shell program accepts arguments in another situation too – whenspecified in the command line itself.

• This non-interactive method of specifying arguments is quite useful for script requiring few inputs.

• When arguments are specified with shell procedure, they are assignedto certain “special variables” or rather “ positional-parameters”

• First argument to $1, second to $2 ,third to $3 and so on….





Example

$ cat emp2.sh

echo “Program: $0

The number of argument specified is $#

The arguments are $* ” grep “ $1” $2

echo “\n job is over”

where $* : stores the complete set of positional parameter

$# : numbers of arguments

$0 : program name.Example:

$ emp2.sh director emp2.lst

Maximum upto 9 arguments can be passed.





Exit Status of a Command

$? - gives the status of the latest command

If the output is :

- 0 , if the command is successful- non-zero if it fails ,

- 2 if the file is unreadable (in dealing with files)

Example :

$ grep director emp.lst > /dev/null ; echo $?Output: $ 0

$ grep manager emp.lst > /dev/null ; echo $?

Output: $ 1 .





The Logical Operators $$ and ||

Conditional Execution

&& operator is used in the same sense as C.

Example :

$ grep ‘director’ emp1.lst && echo “pattern found in file “

Output :

$ 1006|chanchal singhvi| director|sales|7/09/73|6700

pattern found in file

The ‘||’ operator is used to execute the command following only if when theprevious command fails.

Example :

$ grep ‘manager’ emp2.lst || echo “pattern not found”





exit : Script Termination

• The exit statement is used to permanently terminates the program.• When this statement is encountered in a script, execution is halted and control is

returned to the calling program in most cases the shell.

• Need not to be included , shell understand the end of the program.

• Quite often used with a command when it fails.

• Example :$ grep “$1” $2 || exit 2

echo “pattern found – job over”

• The default argument is zero which implies success

• Non-zero values are used to indicates varies errors.





The “if” Condition

• In the shell, the statement uses the following forms, much like the one used inother languages

if (condition) is true

then

Execute command

elseExecute command

fi

• Example :

$ if grep “director” emp.lst

then echo “Pattern found – Job Over”

else echo “Pattern not found”

fi

( contd..)





The “if” Condition ( Contd.. . )

$ 9876 | jai sharma | director | production | 12/03/80|7000Pattern found – Job Over

• Relational operator used by “if” :

Operator Meaning

-eq Equal to

-ne Not equal to

-gt Greater than

-ge Greater than or equal to

-lt Less than

-le Less than or equal to





The “Case” Condition

• Syntax :

case expression in

pattern1) execute commands ;;

pattern2 ) execute commands ;;

pattern3) execute commands ;;esac





The “Case” Condition

$ cat menu.sh

echo “ MENU\n

1.List of files\n 2.Process of user\n 3. Today’s Date 4.Uses of the system\n5. Quit to Unix\n Enter your option: \c”

read choice

case “$choice” in

1)ls –l ;;

2 ) ps –f ;;

3 )date ;;

4)who ;;

5 )exit ;;

esac





expr : Computation

It perform arithmetic operation on integer, and also manipulate strings to a limitedextent.

For $ x=3 y=5

$ expr 3 + 5

Output: $8

$ expr $x - $y

Output: $-2

$ expr 3 \* 5

Output: $15

$ expr $y / $x

Output: $1

$ expr 13 % 5

Output: $3





Sleep And Wait

• Is used in order to introduce some delay in a shell script

For example: If the user needs to see some messages on screen before thescript starts doing something else.

• You may like to make a check regularly (say, once a min) for an event to occur

(say ,for a file to spring into existence)

• Sleep is a UNIX command that introduces this delay.

• Example : sleep 100 ; echo “ 100 seconds have been elapsed”

• O/P 100 seconds have been elapsed





Wait: Command

• wait is a shell built-in command that checks whether all background processhave been completed

• Useful when you have to run a job in the background, and to make sure thecommand is completed so that you can run yet another program.

• Example :

• $ wait # waits for all background command

• $ wait 138 # waits for completion of process PID 138





While : Looping

• Syntax :

while condition is true

do

executedone





Example:$ cat emp5.sh

# Program : emp5.sh - - shows the use of while loop

answer=y

while [‘$answer” = “y” ] # Must it to y first to enter the loop

do

echo “Enter the code and description: \c”

read code description # Read both together echo “$code | $description” >> newlist #Append a line to file

echo “Enter any more (y/n)? \c”

read anymore

case $anymore in

y*|Y*) answer=y ;; #Also accept yes, YES etc.n*| N*)answer=n ;; #Also accept no, NO etc.

*) answer=y ;; #Any other reply means y

esac

done





Setting up an Infinite loop

Example :

while true ; do

df –t

sleep 300

done &

• This is useful if you want to see the free space available on your disc every fivemin.




O ac e Ce te o ce e ce

for : Looping with a List

• The for loop is different in structure from other one used in other programminglanguage

• No next , no step but it uses ‘list ’ instead

• Syntax :

for variable in list

do

execute commands

done

• Additional parameters are variable and list .

• Executes as many times as the items in the list .




Example 1:$ for x in 1234

do

echo “The value of x is $x”

done

Output :

The value of x is 1

The value of x is 2

.

4




Example 2

$ cat test_files.sh

#Checking for particular changes in files

set -x

cd

rm test_result_240.log echo "Checking pattern in files replaced in code control"

for tmpl in `cat ksagar/0004/data/tmpl_lis_240.tpl`

do

echo $tmpl >> test_result_240.log

grep"ABI 02008, CAB 03242, C/C 10280-00" $R_DATA/$tmpl >>test_result_240.log

done

echo "Process completed..."

unix for dba

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