unix shell-scripting basics

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UNIX Shell-Scripting Basics



Agenda

What is a shell? A shell script?

Introduction to bash

Running CommandsApplied Shell Programming



What is a shell?



What is a shell?

/bin/bash



What is a shell?

#!/bin/bash



What is a shell?

INPUT

shell

OUTPUT ERROR



What is a shell?

Any Program But there are a few popular shells…



Bourne Shells

/bin/sh

/bin/bash“Bourne- Again Shell”

Steve Bourne



Other Common Shells

C Shell (/bin/csh)

Turbo C Shell (/bin/tcsh)

Korn Shell (/bin/ksh)



An aside: What do I mean by /bin ?

C Shell (/bin/csh)

Turbo C Shell (/bin/tcsh)

Korn Shell (/bin/ksh)



An aside: What do I mean by /bin ?

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

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

/tmp

/dev /home/borwicjh



What is a Shell Script?

A Text File

With Instructions

Executable



What is a Shell Script?

% cat > hello.sh <<MY_PROGRAM

#!/bin/sh

echo „Hello, world‟ MY_PROGRAM

% chmod +x hello.sh

% ./hello.shHello, world



What is a Shell Script? A Text File


#!/bin/sh


% chmod +x hello.sh




An aside: Redirection

cat > /tmp/myfile

cat >> /tmp/myfile

cat 2> /tmp/myerr

cat < /tmp/myinput cat <<INPUTSome inputINPUT

cat > /tmp/x 2>&1

INPUT

env

OUTPUT ERROR

0

1 2



What is a Shell Script? How To Run


#!/bin/sh


% chmod +x hello.sh




What is a Shell Script? What To Do


#!/bin/sh


% chmod +x hello.sh




What is a Shell Script? Executable


#!/bin/sh


% chmod +x hello.sh




What is a Shell Script? Running it


#!/bin/sh


% chmod +x 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



Variables and the Environment

% hello.sh

bash: hello.sh: Command notfound

% PATH=“$PATH:.”

% hello.sh

Hello, world



An aside: Quoting

% echo „$USER‟ $USER% echo “$USER”

borwicjh% echo “\”” ” % echo “deacnet\\sct”

deacnet\sct% echo „\”‟ \”



Variables and the Environment

% env[…variables passed to sub-programs…] % NEW_VAR=“Yes”

% echo $NEW_VARYes% env[…PATH but not NEW_VAR…]

% export NEW_VAR% env[…PATH and NEW_VAR…]



Welcome to Shell Scripting!



How to Learn

manman bash

man cat

man man man –kman –k manual

Learning the Bash Shell , 2nd Ed.

“Bash Reference” Cards

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



Introduction to bash



Continuing Lines: \

% echo This \

Is \

A \

Very \

Long \

Command Line

This Is A Very Long Command Line

%



Exit Status

$?

0 is True

% ls /does/not/exist

% echo $?

1

% echo $?

0



Exit Status: exit

% cat > test.sh <<_TEST_

exit 3

_TEST_% chmod +x test.sh

% ./test.sh

% echo $?3



Logic: test

% test 1 -lt 10

% echo $?

0% test 1 == 10

% echo $?

1



Logic: test

test

[ ]

[ 1 –lt 10 ]

[[ ]]

[[ “this string” =~ “this” ]]

(( ))

(( 1 < 10 ))



Logic: test

[ -f /etc/passwd ]

[ ! –f /etc/passwd ]

[ -f /etc/passwd –a –f /etc/shadow ]

[ -f /etc/passwd –o –f /etc/shadow ]



An aside: $(( )) for Math

% echo $(( 1 + 2 ))

3

% echo $(( 2 * 3 ))6

% echo $(( 1 / 3 ))

0



Logic: if

if something

then

:

# “elif” a contraction of “else if”:

elif something-else

then

:

else

then

:

fi



Logic: if

if [ $USER –eq “borwicjh” ]

then

:

# “elif” a contraction of “else if”:

elif ls /etc/oratab

then

:

else

then

:

fi



Logic: if

# see if a file exists

if [ -e /etc/passwd ]

thenecho “/etc/passwd exists”

else

echo “/etc/passwd not found!” fi



Logic: for

for i in 1 2 3

do

echo $idone



Logic: for

for i in /*

do

echo “Listing $i:” ls -l $i

read

done



Logic: for

for i in /*

do

echo “Listing $i:”

ls -l $i

read

done



Logic: C-style for

for (( expr1 ;

expr2 ;

expr3 ))

do

listdone



Logic: C-style for

LIMIT=10

for (( a=1 ;

a<=LIMIT ;

a++ ))

do

echo –n “$a ” done



Logic: while

while something

do

:

done



Logic: while

a=0; LIMIT=10

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

do

echo -n "$a ”

a=$(( a + 1 ))

done



Counters

COUNTER=0

while [ -e “$FILE.COUNTER” ]

do

COUNTER=$(( COUNTER + 1))

done

Note: race condition



Reusing Code: “Sourcing”

% cat > /path/to/my/passwords <<_PW_

FTP_USER=“sct”

_PW_

% echo $FTP_USER

% . /path/to/my/passwords

% echo $FTP_USER

sct

%



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



It takes a long time to become a bash guru…



Running Programs



Reasons for Running Programs

Check Return Code

$?

Get Job Output

OUTPUT=`echo “Hello”`

OUTPUT=$(echo “Hello”)

Send Output Somewhere

Redirection: <, >

Pipes



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!



Email Notification

% echo “Message” | \

mail –s “Here‟s your message” \

[email protected]



Dates

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

% echo $DATESTRING

20060125

% man date



FTP the Hard Way

ftp –n –u server.wfu.edu <<_FTP_

user username password

put FILE

_FTP_



FTP with wget

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

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



FTP with curl

curl –T upload-file \

-u username:password \

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



Searching: grep

% grep rayra /etc/passwd

% grep –r rayra /etc

% grep –r RAYRA /etc

% grep –ri RAYRA /etc

% grep –rli rayra /etc



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



Searching: locate

% locate .lis

[files with .lis in path]

% locate log

[also finds “/var/log/messages”]



Applied Shell Programming



Make Your Life Easier

TAB completion

Control+R

history

cd -

Study a UNIX Editor



pushd/popd

% cd /tmp% pushd /var/log

/var/log /tmp

% cd ..% pwd

/var

% popd/tmp



Monitoring processes

ps

ps –ef

ps –u oracle

ps –C sshd

man ps



“DOS” Mode Files

#!/usr/bin/bash^M

FTP transfer in ASCII, or

dos2unix infile > outfile



sqlplus

JOB=“ZZZTEST”

PARAMS=“ZZZTEST_PARAMS”

PARAMS_USER=“BORWICJH”

sqlplus $BANNER_USER/$BANNER_PW << _EOF_

set serveroutput on

set sqlprompt ""

EXECUTE WF_SATURN.FZ_Get_Parameters('$JOB','$PARAMS', '$PARAMS_USER');

_EOF_



sqlplus

sqlplus $USER/$PASS @$FILE_SQL \$ARG1 $ARG2 $ARG3

if [ $? –ne 0 ]then

exit 1fiif [ -e /file/sql/should/create ]then[…use SQL- created file…]

fi

Ask Amy Lamy!



Passing Arguments

% cat > test.sh <<_TEST_

echo “Your name is \$1 \$2”

_TEST_

% chmod +x test.sh

% ./test.sh John Borwick ignore-this

Your name is John Borwick



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



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



Other Questions?

Shells and Shell Scripts

bash

Running Commands

bash and Banner in Practice

unix shell-scripting basics

Documents