Summary shell script for DBA

Arithmetic Operators
Operator	Description
-eq	True if two integers are equal
-ne	True if two integers are not equal
-lt	True if operand1 is less than operand2
-le	True if operand1 is less than or equal to operand2
-gt	True if operand1 is greater than operand2
-ge	True if operand1 is greater than or equal to operand2

String Operators
String Operator	Description
-z string	True if the string is empty
-n string	True if the string is not empty
string1 = string2	True if the strings are equal
string1 != string2	True if the strings are not equa
string1 < string2	True if string1 sorts before string2
string1 > string2	True if string1 sorts after string2

Files Operators
File Operator	Description
-a	True if file exists
-b	True if file is a block device file
-c	True if file is a character device file
-d	True if file is a directory
-e	True if file exists
-f	True if file exists and is a regular file
-g	True if file has set-group-id permission set
-h	True if file is a symbolic link
-L	True if file is a symbolic link
-k	True if file’s sticky bit is set
-p	True if file is a named pipe
-r	True if the file is readable (by current user)
-s	True if file exists and is not empty
-S	True if file is socket
-u	True if file is set-user-id
-w	True if file is writable (by current user)
-x	True if file is executable
-O	True if file is effectively owned by current user
-G	True if file is effectively owned by current user’s group
-N	True if file has been modified since it was last read
file1 -nt file2	True if operand1 is greater than or equal to operand2
file1 -ot file2	True if operand1 is greater than or equal to operand2
file1 -ef file2	True if file1 is a hard link to file2

Common Character Matching Patterns
Parttern	Description
a|b	Matches either an a or a b
*	Matches any string of characters, often used for a catchall
[abc]	Matches any character a, b, or c
[a-c]	Matches any character a, b, or c
[0-9]	Matches any character 0 through 9
"<string>"	Matches the string enclosed in the quotes

Special Shell Variables
Name	Description
$1 - $n	Positional parameters that hold values for parameters passed to the script.
$?	The exit status of the last command. Contains a 0 for successfully executed commands.   Contains a nonzero value for commands that failed.  This nonzero value depends on what the command actually returned.
$0	Within a shell script, contains the name of the shell script being executed.
$#	The number of positional parameters passed to a script.
$$	The process number of the shell. Can be used to generate unique file names.
$!	The process number of the most recently executed background process.
$*	Contains all the positional parameters passed to the script.

Testing a Condition

[ operand1 operator operand2 ]

Control Structures

if/then/else statement

Syntax	Examples
if condition ; then     commands else     commands if if condition ; then     commands elsif condition     commands elsif condition     commands if	#!/bin/bash thresh=1048576 totMem=$(grep MemTotal /proc/meminfo | awk '{print $2}') if [ $totMem -lt $thresh ]; then   echo "Total Memory $totMem is less than: $thresh"   exit 1 else   echo "Total Memory is: $totMem" fi

case statement

Syntax

Examples

case expression in     pattern1)         commands ;;     pattern2)         commands ;; esac

#!/bin/bash archLoc=/dev/sdb2 usedSpc=$(df -h $archLoc | awk '{print $5}' | grep -v Use | cut -d "%" -f1 - ) case $usedSpc in   [0-9])     arcStat="relax, lots of disk space: $usedSpc"   ;;   [1-7][0-9])     arcStat="disk space okay: $usedSpc"   ;;   [8][0-9])     arcStat="gulp, space getting low: $usedSpc"   ;;   [9][0-9])     arcStat="red alert, running out of space: $usedSpc"   ;;   [1][0][0])     arcStat="update resume, no space left; $usedSpc"   ;;   *)     arcStat="huh?: $usedSpc" esac BOX=$(uname -a | awk '{print $2}') echo "archive space on: $BOX $arcStat" exit 0

for loop

Syntax

Examples

for name [in list] do   commands can use $name done

#!/bin/bash LOC_LIST="/backup /u01 /u02 /u03" msg="" for curLoc in $LOC_LIST do   usedSpc=$(df -h $curLoc | awk '{print $5}' | grep -v Use | cut -d "%" -f1 - )   case $usedSpc in     [0-8][0-9])       msg="Space getting low: $curLoc on $(uname -a | awk '{print $2}') is used ${usedSpc}%"     ;;     [9][0-9])       msg="Running out of space: $curLoc on $(uname -a | awk '{print $2}') is used ${usedSpc}%"     ;;     [1][0][0])       msg="No space left: $curLoc on $(uname -a | awk '{print $2}') is used ${usedSpc}%"     ;;   esac done if [ -n "$msg" ] ; then   echo $msg fi exit 0

Command substitution

There are two techniques for archiving command substitution in shell script:
variable=$(shell commands)
variable=`shell commands`

$BOX=$(uname -a | awk '{print$2}')
$BOX=`uname -a | awk '{print$2}'`

Either technique is a valid method. Depending on which shell you use, the $(command) command substitution might not be available.

Other example:

Pgm=$(basename $0)
if [ $# -ne 1 ]
then
  echo "Wrong number of parameters passed to script."
  echo "Usage: $Pgm ORACLE_SID"
  exit 1
fi

.