Question

UNIX QUESTION

Exercise #1. [8 Marks] Create a script that does the following:

a. Takes 4 input parameters b. Using the shell special variables print the following:

i. The command you executed

ii. First input

iii. Second input

iv. Third input

v. Fourth Input

vi. Process Id

vii. Total number of input parameters [ by querying the system for it ]

Exercise #2. [8 Marks] Creates a script that does the following:

a. Takes two input parameters

b. Using the numeric comparison syntax, it tests and prints whether the first input in relation to the second input is

: i. Greater than

ii. Greater than or equal

iii. Less than

iv. Less than or equal

v. Equal

vi. Not equal

c. Using the string comparison syntax, it tests and prints whether the first input in relation to the second input is

i. Greater than

ii. Greater than or equal

iii. Less than

iv. Less than or equa

l v. Equal vi. Not equal

b. Use the following pairs to test your code:

i. 123 14

ii. 55 55

iii. Bad Band

iv. bad Band

v. chaos banana

Exercise #3 [4 Marks] Creates a script that explores the content of a directory, and does the following:

a. Takes as an input the name of a folder at your current working directory

b. Prints the time and date to a file called dirLog which is located at your current working directory

c. Loops through the content of the directory and appends the name of each file found to a file called dirLog

Answer 1

script1.sh

#! /bin/bash

# this can be used to check the number of arguments passed
# but it is not required as part vii. asks for total number of input parameters
if [[ $# -ne 4 ]]; then
exit 1
fi

# you can also use just 1 echo command to display each parameter required as
# echo $0 $1 $2 $3 $4 $$ $#
echo $0
echo $1
echo $2
echo $3
echo $4
echo $$
echo $#

script2.sh

#! /bin/bash

if [[ $# -ne 2 ]]; then
exit 1
fi

# Uncomment the following code for a somewhat smarter comparison rather than checking all
# if [[ $1 -eq $2 ]]; then
# echo "$1 = $2"
## you can also add statements for greater than or equal to
## but that seems redundant
# else
# echo "$1 != $2"
# if [[ $1 -gt $2 ]]; then
# echo "$1 > $2"
# else
# echo "$1 < $2"
# fi
# fi

# Using numeric comparison
# use the following regular expression to check if the input parameters are numbers
re='^[0-9]+$'
if [[ $1 =~ $re && $2 =~ $re ]]; then
if [[ $1 -gt $2 ]]; then
echo "$1 > $2"
fi

if [[ $1 -ge $2 ]]; then
echo "$1 >= $2"
fi

if [[ $1 -lt $2 ]]; then
echo "$1 < $2"
fi

if [[ $1 -le $2 ]]; then
echo "$1 <= $2"
fi

if [[ $1 -eq $2 ]]; then
echo "$1 = $2"
fi

if [[ $1 -ne $2 ]]; then
echo "$1 != $2"
fi
fi

# Using string comparison
if [[ $1 > $2 ]]; then
echo "string \"$1\" > string \"$2\""
fi

if [[ $1 > $2 || $1 == $2 ]]; then
echo "string \"$1\" >= string \"$2\""
fi

if [[ $1 < $2 ]]; then
echo "string \"$1\" < string \"$2\""
fi

if [[ $1 < $2 || $1 == $2 ]]; then
echo "string \"$1\" <= string \"$2\""
fi

if [[ $1 == $2 ]]; then
echo "string \"$1\" = string \"$2\""
fi

if [[ $1 != $2 ]]; then
echo "string \"$1\" != string \"$2\""
fi

script3.sh

#! /bin/bash

if [[ $# -eq "1" && -d "$1" ]]; then
date > dirLog
# No need to loop, we can use the output of the ls command for this
# uncomment the following if you need to use a loop
# for file in "$1/*"; do
# echo $file
# done
ls $1 >> dirLog
else
exit 1
fi

OUTPUT:

Contents of dirLog after executing script3.sh. Note that date -u can be specified for utc time

Script Screenshots:

script1.sh

script2.sh

script3.sh