Basic Shell Scripting Practice - hpc.lsu.edu · Loop Exercise 1. Print out the contents of the current directory ... s substitution ... Use awk to print out the entire fields of uptime

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Basic Shell Scripting Practice

Quotation Exercise

1.  Printoutyour$LOGNAME2.  Printdate3.  Print`whoami`4.  Printyourcurrentdirectory

Basic Shell Scripting 2

Quotation Exercise

#!/bin/bash

echo "Hello, $LOGNAME"echo "Current date is `date`"echo "User is `who i am`"echo "Current directory `pwd`”

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Number Exercise

1.  a=5.66;b=8.672.  Printoutsumofa+b3.  z=54.  Printoutresultofz+5

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Number Exercise

#!/bin/bash

a=5.66b=8.67c=`echo $a + $b | bc`echo "$a + $b = $c"

z=5z=`expr $z + 3`echo "z=$z"z=$(($z+5))echo "z=$z”

5 Basic Shell Scripting

Loop Exercise

1.  Loopthroughalistofplanets(MercuryVenusEarthMarsJupiterSaturnUranusNeptunePluto)

2.  Printoutlistelementonebyone

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Loop Exercise

#!/bin/bash

for planet in Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Plutodo echo $planetdone

7 Basic Shell Scripting

Loop Exercise

1.  Printoutthecontentsofthecurrentdirectory

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Loop Exercise

#!/bin/bash

for file in `ls`do

echo $file

done

9 Basic Shell Scripting

Function Exercise

1.  Createa“hello”funcVonrequiringanameasparameterandprintout“helloname”

2.  CallthefuncVontwicewithdifferentparameters

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Function Exercise

#!/bin/bash# Passing arguments to a functionhello () { echo Hello $1}hello John hello James

11 Basic Shell Scripting

grep & egrep •  grep: Unix utility that searches through either information piped to it

or files. •  Usage: grep <options> <search pattern> <files> •  Options:

-i ignore case during search -r,-R search recursively -v invert match i.e. match everything except pattern -l list files that match pattern -L list files that do not match pattern -n prefix each line of output with the line number within its input file. -A num print num lines of trailing context after matching lines. -B num print num lines of leading context before matching lines.

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grep Examples •  Search files containing the word bash in current directory

•  Repeat above search using a case insensitive pattern match and print line number that matches the search pattern

grep bash *

grep -in bash *

•  Search files NOT containing the word bash in current directory grep -v bash *

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grep Examples

•  grep OR : find people either manager or in sales dept

100ThomasManagerSales$5,000200JasonDeveloperTechnology$5,500300RajSysadminTechnology$7,000500RandyManagerSales$6,000

grep ‘Manager\|Sales’ employee.txt -> 100ThomasManagerSales$5,000

500RandyManagerSales$6,000

•  grep AND: find people who is both sysadmin and in Tech dept

grep –i ‘sysadmin.*Technology’ employee.txt -> 100300RajSysadminTechnology$7,000

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sed commands and flags Flags Operation Command Operation -e combine multiple

commands s substitution

-f read commands from file g global replacement -h print help info p print -n disable print i ignore case -V print version info d delete -r use extended regex G add newline

w write to file x exchange pattern with hold

buffer h copy pattern to hold buffer ; separate commands

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sed Examples

#!/bin/bash

# My First Script

echo "Hello World!”

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sed Examples (1)

•  Add flag -e to carry out multiple matches. •  Replace bash with tcsh and Frist with Second

•  Alternate form with ; instead of -e

•  The default delimiter is slash (/), try : in place of /

cat hello.sh | sed -e ’s/bash/tcsh/g’ -e ’s/First/Second/g’

sed ’s/bash/tcsh/g; s/First/Second/g’ hello.sh

sed ’s:/bin/bash:/bin/tcsh:g’ hello.sh

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sed Examples (2)

•  Delete blank lines from a file

•  Delete line n through m in a file

sed ’/^$/d’ hello.sh

sed ’2,4d’ hello.sh

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awk Syntax awk pattern {action} pattern decides when action is performed Actions:•  Most common action: print •  Print file dosum.sh:

awk ’{print $0}’ dosum.sh

•  Print line matching files in all .sh files in current directory:

awk ’/bash/{print $0}’ *.sh •  $0 Print the entire line, use. •  NR #records (lines)

•  NF #fields or columns in the current line. •  By default the field delimiter is space or tab. To change the field

delimiter use the -F<delimiter> command.

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uptime 11:18am up 14 days 0:40, 5 users, load average: 0.15, 0.11, 0.17 Use awk to print out the entire fields of uptime results uptime | awk ’{print $0}’ Print out current time and #fields uptime | awk ’{print $1,NF}’ 11:18am 12 Print out # of users uptime | awk –F, ’{print $1}’ 5 users

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AwkExamples