Operating Systems and Systems Integration

SOLUTIONS Shell Programming—an Introduction
1. This is hello1: #! /bin/sh echo Hello $@ or (here is hello2): #! /bin/sh echo -n "Hello " for i do echo -n "$i " done echo 2. Here is some typical output: $ sh hello1 Nick Urbanik Hello Nick Urbanik $ sh -x hello1 Nick Urbanik + echo Hello Nick Urbanik Hello Nick Urbanik $ sh -x hello2 Nick Urbanik + echo -n ’Hello ’ Hello + echo -n ’Nick ’ Nick + echo -n ’Urbanik ’ Urbanik + echo $ sh -v hello1 Nick Urbanik #! /bin/sh echo -n "Hello " $ sh -v ./hello2 Nick Urbanik #! /bin/sh echo -n "Hello " Hello for i do echo -n "$i " done Nick Urbanik echo

From the manual page of bash:
Nick Urbanik <nicku(at)vtc.edu.hk> ver. 1.1

SOLUTIONS Shell Programming—an Introduction Operating Systems and Systems Integration

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-v Print shell input lines as they are read. -x After expanding each simple command, display the expanded value of PS4, followed by the command and its expanded arguments.
PS4 is a prompt used in tracing execution, which as you can see above, is normally set to “+ ”. 3. #! /bin/sh [ $# -ne 2 ] && echo $0 start finish && exit start=$1 end=$2 i=$start while [ $i -le $end ] do echo -n "$i " i=$(expr $i + 1) done echo The question asks for a while loop, so let’s use easier arithmetic evaluation notation: #! /bin/sh [ $# -ne 2 ] && echo $0 start finish && exit start=$1 end=$2 i=$start while (( i <= end )) do echo -n "$i " (( ++i )) done echo Let’s see an answer using the alternative for loop syntax with arithmetic evaluation: #! /bin/sh [ $# -ne 2 ] && echo $0 start finish && exit start=$1 end=$2 for (( i = start; i <= end; ++i )) do echo -n "$i " done echo 4. #! /bin/sh for file in *.rpm
Nick Urbanik <nicku(at)vtc.edu.hk> ver. 1.1

SOLUTIONS Shell Programming—an Introduction Operating Systems and Systems Integration

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do rpm -K $file echo done 5. #! /bin/sh # for file in r*.rpm emacs*.rpm for file in *.rpm do OUT=$(rpm -K $file) > /dev/null 2>&1 if echo $OUT | grep -v ’md5 gpg OK’ > /dev/null 2>&1 then echo BAD $OUT else : # echo GOOD $OUT fi done 6. #! /bin/sh if ! grep admins /etc/group > /dev/null 2>&1 then groupadd admins done

Nick Urbanik <nicku(at)vtc.edu.hk>

ver. 1.1