Shell Scripts (Linux) Code so far (bottom of page): Write a script called \'pars

Question

Shell Scripts (Linux)

Code so far (bottom of page):

Write a script called 'parser' with the following usage:

There are two forms for the script.

The first form simply displays the usage statement, -h is a flag for help. Unacceptable syntax or -h should display the usage statement.

The second form must contain a mandatory username with an optional -h or -f argument. The script will display whether or not the username is logged on. One way to do this is to use the following command and do a comparison on the resulting count (assuming you created the username variable in your script):

When the -h option is specified, show the usage statement as above. When the -f option is specified, it must be followed by a filename. The -f option will display the number of lines in filename, if the file exists.

The script should allow for all optional and mandatory command line arguments to be in any order. The script must trap for the following fatal errors, display an appropriate message and exit:

1) A filename does not follow the -f switch

2) The filename passed does not exist in the current directory

3) An illegal switch is passed

4) The mandatory username is not given when the -f switch is given, even if a filename is given

5) Too many arguments are given

6) Too few arguments are given (i.e. the user does not give at least 'parser -h' or 'parser <username>')

Code so far:

#!/bin/bash

show_help () {
echo "$0 [-h]"
echo "$0 [-h] [-u username] [-f filename]"
}
user_proc () {
num=$(ps -u $1 | wc -l)
echo "user $1 owns $num processes"
}
file_type () {
if [ -f "$1" ]
then
echo "$1 exists and is a regular file"
elif [ -d "$1" ]
then
echo "$1 exists and is a directory"
elif [ -e "$1" ]
then
echo "$1 exists but is something else"
else
echo "$1 does not exist"
fi
}
is_flag () {
if [[ $1 == -* || -z "$1" ]]
then
echo "Invalid argument $1"
exit 3
fi
}

if [ $# -eq 0 ]
then
show_help
exit 1
fi

while [ $# -gt 0 ]
do
case $1 in
"-h")
show_help
shift
;;
"-f")
is_flag $2
file_type $2
shift;shift
;;
"-u")
is_flag $2
user_proc $2
shift 2
;;
*)
echo "Unexpected argument"
exit 2
;;
esac
done

USAGE: parser [-h] parser [-f filename] [-h] username

Explanation / Answer

#!/bin/bash

show_help () {

echo "$0 [-h]"

echo "$0 [-h] [-u username] [-f filename]"

}

file_type () {

if [ -f "$1" ]

then

echo "$1 exists and is a regular file"

elif [ -d "$1" ]

then

echo "$1 exists and is a directory"

elif [ -e "$1" ]

then

echo "$1 exists but is something else"

exit -1

else

echo "$1 does not exist"

exit -1

fi

}

is_flag () {

if [[ $1 == -* || -z "$1" ]]

then

echo "Invalid argument $1"

exit 3

fi

}

is_uname () {

t=`echo $1 | egrep "([a-zA-Z0-9_-]+)" | wc -l`

if [[ t -gt 1 ]]

then

echo "$1 is uname"

exit -1

fi

tmp=`who | grep $1 | wc -l`

if [[ tmp -gt 0 ]]

then

echo "$1 is logged on"

exit -1

fi

}

if [ $# -eq 0 ]

then

show_help

exit 1

fi

if [ $# -gt 4 ]

then

echo "Too many arguments"

exit 1

fi

while [ $# -gt 1 ]

do

case $1 in

"-h")

show_help

shift

;;

"-f")

is_flag $2

for last; do true; done

  

  

is_uname $last

file_type $2

echo "No of lines in the file"

wc -l $2 | awk ' {print $1} '

shift;shift

;;

  

*)

echo "Unexpected argument"

exit 2

;;

esac

done

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