Unix Shell Scripting Basics

Agenda What is a shell? A shell script? Introduction to bash Running Commands Applied Shell Programming

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.sh Hello, world

What is a Shell Script? A Text File % cat > hello.sh <<MY_PROGRAM #!/bin/sh echo ‘Hello, world’ MY_PROGRAM % chmod +x hello.sh % ./hello.sh Hello, world

An aside: Redirection cat > /tmp/myfile cat >> /tmp/myfile cat 2> /tmp/myerr cat < /tmp/myinput cat <<INPUT Some input INPUT cat > /tmp/x 2>&1 0 1 2 INPUT env OUTPUT ERROR

What is a Shell Script? How To Run % cat > hello.sh <<MY_PROGRAM #!/bin/sh echo ‘Hello, world’ MY_PROGRAM % chmod +x hello.sh % ./hello.sh Hello, world

What is a Shell Script? What To Do % cat > hello.sh <<MY_PROGRAM #!/bin/sh echo ‘Hello, world’ MY_PROGRAM % chmod +x hello.sh % ./hello.sh Hello, world

What is a Shell Script? Executable % cat > hello.sh <<MY_PROGRAM #!/bin/sh echo ‘Hello, world’ MY_PROGRAM % chmod +x hello.sh % ./hello.sh Hello, world

What is a Shell Script? Running it % cat > hello.sh <<MY_PROGRAM #!/bin/sh echo ‘Hello, world’ MY_PROGRAM % chmod +x hello.sh % ./hello.sh Hello, world

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 not found % 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_VAR Yes % env […PATH but not NEW_VAR…] % export NEW_VAR % env […PATH and NEW_VAR…]

Welcome to Shell Scripting! Shebang! The Environment PATH Input, Output, and Error chmod

How to Learn man man bash man cat man man man –k man –k manual Learning the Bash Shell , 2 nd Ed. “ Bash Reference” Cards http://www.tldp.org/LDP/abs/html/

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 ] then echo “/etc/passwd exists” else echo “/etc/passwd not found!” fi

Logic: for for i in 1 2 3 do echo $i done

Logic: for for i in /* do echo “Listing $i:” ls -l $i read done

Logic: C-style for for (( expr1 ; expr2 ; expr3 )) do list done

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…

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_address]

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:pass@server.wfu.edu/file wget –r \ ftp://user:pass@server.wfu.edu/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”]

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 1 fi if [ -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

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