UNIX Shell-Scripting Basics

UNIX Shell-Scripting Basics

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Agenda

What is a shell? A shell script?

Introduction to bash

Running Commands

Applied Shell Programming


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What is a shell?


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What is a shell?

/bin/bash


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What is a shell?

#!/bin/bash


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What is a shell?

INPUT

shell

OUTPUT ERROR


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What is a shell?

Any Program

But there are a few popular shells


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Bourne Shells

/bin/sh

/bin/bash Bourne-Again Shell

Steve Bourne


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Other Common Shells

C Shell (/bin/csh)

Turbo C Shell (/bin/tcsh)

Korn Shell (/bin/ksh)


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An aside: What do I mean by /bin ?

C Shell (/bin/csh)

Turbo C Shell (/bin/tcsh)

Korn Shell (/bin/ksh)


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An aside: What do I mean by /bin ?

/bin, /usr/bin, /usr/local/bin

/sbin, /usr/sbin, /usr/local/sbin

/tmp

/dev

/home/borwicjh


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What is a Shell Script?

A Text File

With Instructions

Executable


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What is a Shell Script?

% cat > hello.sh

What is a Shell Script? A Text File

% cat > hello.sh

An aside: Redirection

cat > /tmp/myfile

cat >> /tmp/myfile

cat 2> /tmp/myerr

cat < /tmp/myinput

cat &1

INPUT

env

OUTPUT ERROR

0

1 2


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What is a Shell Script? How To Run

% cat > hello.sh

What is a Shell Script? What To Do

% cat > hello.sh

What is a Shell Script? Executable

% cat > hello.sh

What is a Shell Script? Running it

% cat > hello.sh

Finding the program: PATH

% ./hello.sh

echo vs. /usr/bin/echo

% echo $PATH /bin:/usr/bin:/usr/local/bin: /home/borwicjh/bin

% which echo /usr/bin/echo


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Variables and the Environment

% hello.sh

bash: hello.sh: Command not found

% PATH=$PATH:.

% hello.sh

Hello, world


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An aside: Quoting

% echo $USER $USER % echo $USER borwicjh % echo \ % echo deacnet\\sct deacnet\sct % echo \ \


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Variables and the Environment

% env [variables passed to sub-programs] % NEW_VAR=Yes % echo $NEW_VAR Yes % env [PATH but not NEW_VAR] % export NEW_VAR % env [PATH and NEW_VAR]


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Welcome to Shell Scripting!


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How to Learn

man man bash

man cat

man man

man k man k manual

Learning the Bash Shell, 2nd Ed.

Bash Reference Cards

http://www.tldp.org/LDP/abs/html/


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Introduction to bash


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Continuing Lines: \

% echo This \

Is \

A \

Very \

Long \

Command Line

This Is A Very Long Command Line

%


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Exit Status

$?

0 is True

% ls /does/not/exist

% echo $?

1

% echo $?

0


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Exit Status: exit

% cat > test.sh

Logic: test

% test 1 -lt 10

% echo $?

0

% test 1 == 10

% echo $?

1


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Logic: test

test

[ ] [ 1 lt 10 ]

[[ ]] [[ this string =~ this ]]

(( )) (( 1 < 10 ))


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Logic: test

[ -f /etc/passwd ]

[ ! f /etc/passwd ]

[ -f /etc/passwd a f /etc/shadow ]

[ -f /etc/passwd o f /etc/shadow ]


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An aside: $(( )) for Math

% echo $(( 1 + 2 ))

3

% echo $(( 2 * 3 ))

6

% echo $(( 1 / 3 ))

0


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Logic: if

if something

then

:

# elif a contraction of else if:

elif something-else

then

:

else

then

:

fi


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Logic: if

if [ $USER eq borwicjh ]

then

:

# elif a contraction of else if:

elif ls /etc/oratab

then

:

else

then

:

fi


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Logic: if

# see if a file exists

if [ -e /etc/passwd ]

then

echo /etc/passwd exists

else

echo /etc/passwd not found!

fi


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Logic: for

for i in 1 2 3

do

echo $i

done


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Logic: for

for i in /*

do

echo Listing $i:

ls -l $i

read

done


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Logic: C-style for

for (( expr1 ;

expr2 ;

expr3 ))

do

list

done


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Logic: C-style for

LIMIT=10

for (( a=1 ;

a

Logic: while

while something

do

:

done


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Logic: while

a=0; LIMIT=10

while [ "$a" -lt "$LIMIT" ]

do

echo -n "$a

a=$(( a + 1 ))

done


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Counters

COUNTER=0

while [ -e $FILE.COUNTER ]

do

COUNTER=$(( COUNTER + 1))

done

Note: race condition


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Reusing Code: Sourcing

% cat > /path/to/my/passwords

Variable Manipulation

% FILEPATH=/path/to/my/output.lis

% echo $FILEPATH

/path/to/my/output.lis

% echo ${FILEPATH%.lis}

/path/to/my/output

% echo ${FILEPATH#*/}

path/to/my/output.lis

% echo ${FILEPATH##*/}

output.lis


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It takes a long time to

become a bash

guru


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Running Programs


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Reasons for Running Programs

Check Return Code $?

Get Job Output OUTPUT=`echo Hello`

OUTPUT=$(echo Hello)

Send Output Somewhere Redirection:

Pipes


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Pipes

Lots of Little Tools

echo Hello | \

wc -c

INPUT

echo

OUTPUT ERROR

0

1 2

INPUT

wc

OUTPUT ERROR

0

1 2

A Pipe!


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Email Notification

% echo Message | \

mail s Heres your message \

[email protected]


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Dates

% DATESTRING=`date +%Y%m%d`

% echo $DATESTRING

20060125

% man date


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FTP the Hard Way

ftp n u server.wfu.edu

FTP with wget

wget \ ftp://user:[email protected]/file

wget r \ ftp://user:[email protected]/dir/


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FTP with curl

curl T upload-file \

-u username:password \

ftp://server.wfu.edu/dir/file


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Searching: grep

% grep rayra /etc/passwd

% grep r rayra /etc

% grep r RAYRA /etc

% grep ri RAYRA /etc

% grep rli rayra /etc


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Searching: find

% find /home/borwicjh \

-name *.lis

[all files matching *.lis]

% find /home/borwicjh \

-mtime -1 name *.lis

[*.lis, if modified within 24h]

% man find


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Searching: locate

% locate .lis

[files with .lis in path]

% locate log

[also finds /var/log/messages]


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Applied Shell Programming


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Make Your Life Easier

TAB completion

Control+R

history

cd -

Study a UNIX Editor


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pushd/popd

% cd /tmp

% pushd /var/log

/var/log /tmp

% cd ..

% pwd

/var

% popd

/tmp


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Monitoring processes

ps

ps ef

ps u oracle

ps C sshd

man ps


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DOS Mode Files

#!/usr/bin/bash^M

FTP transfer in ASCII, or

dos2unix infile > outfile


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sqlplus

JOB=ZZZTEST

PARAMS=ZZZTEST_PARAMS

PARAMS_USER=BORWICJH

sqlplus $BANNER_USER/$BANNER_PW

sqlplus

sqlplus $USER/$PASS @$FILE_SQL \ $ARG1 $ARG2 $ARG3 if [ $? ne 0 ] then exit 1 fi if [ -e /file/sql/should/create ] then [use SQL-created file] fi Ask Amy Lamy!


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Passing Arguments

% cat > test.sh

INB Job Submission Template

$1: user ID

$2: password

$3: one-up number

$4: process name

$5: printer name

% /path/to/your/script $UI $PW \

$ONE_UP $JOB $PRNT


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Scheduling Jobs

% crontab -l

0 0 * * * daily-midnight-job.sh

0 * * * * hourly-job.sh

* * * * * every-minute.sh

0 1 * * 0 1AM-on-sunday.sh

% EDITOR=vi crontab e

% man 5 crontab


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Other Questions?

Shells and Shell Scripts

bash

Running Commands

bash and Banner in Practice


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UNIX Shell-Scripting Basics

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Transcript of UNIX Shell-Scripting Basics