Basic practice of the if/then/else syntax for numerical comparators. Given a skeleton script to flesh out, you’ll practice how to use conditional expressions to change a program’s output depending on what arguments are passed into the script.
The basic-ifelse.sh, when run from the command-line with a set of given arguments, should return output exactly as specified in the Output section.
You can make a copy of the sample skeleton script and modify it.
You will want to be familiar with conditional branching with if/elif/else statements, how to write a reusable script, and how to test number of arguments and how to compare arguments
You are welcome to use the script below and fill in the parts needed to complete the assignment:
# skeleton basic-ifelse.sh
# if there are fewer than 1 arguments, i.e. 0
if [[ "$#" -lt 1 ]]; then
echo "You need at least one argument"
elif [[ "$#" -eq 1 ]]; then
# just one argument
echo "There is just one argument: $1"
elif [[ "$#" -eq 2 ]]; then
echo "(fix this line yourself)"
if [[ $1 -eq $2 ]]; then
echo "$1 is equal to $2"
## write the other conditions for less-than and
## greater-than yourself
fi
elif [[ "$#" -eq 3 ]]; then
echo "There are three arguments: $1, $2, and $3"
# There are a few ways to do this next part, I'm going with
# the strategy of having one string variable for dealing
# with comparing $1 to $2, and the other string for $1 vs $3,
# and then concatenating them at the end.
# You can fill out what I've done, or come up with
# your own branching logic
if [[ $1 -eq $2 ]]; then
str_a="is equal to $2"
elif [[ $1 -lt $2 ]]; then
str_a="is less than $2"
## and so forth
fi
if [[ $1 -eq $3 ]]; then
str_b="is equal to $3"
## and so forth
fi
# finally, echo the full comparison statement
echo "$1 $str_a and $str_b"
### Almost done
### You need to write in one last conditional branch to deal with
### more than 3 arguments, i.e.
### "You need fewer than 9 arguments"
fi
Here is what your basic-ifelse.sh script should return in each of the scenarios below:
# If no arguments are passed in
user@host:~$ bash basic-ifelse.sh
You need more than 0 arguments
# If more than 3 arguments are passed in
user@host:~$ bash basic-ifelse.sh 100 200 300 400
You need fewer than 4 arguments
# If more than 3 arguments are passed in
user@host:~$ bash basic-ifelse.sh 100 200 300 400 500
You need fewer than 5 arguments
# If only one argument is passed in
user@host:~$ bash basic-ifelse.sh 9
The only argument is 9
# If two arguments are passed in and they are equal
user@host:~$ bash basic-ifelse.sh 9 9
There are two arguments: 9 and 9
9 is equal to 9
# If two arguments are passed in and the first is less than the second
user@host:~$ bash basic-ifelse.sh 9 10
There are two arguments: 9 and 10
9 is less than 10
# If two arguments are passed in and the first is greater than the second
user@host:~$ bash basic-ifelse.sh 14 6
There are two arguments: 14 and 6
14 is greater than 6
# If three arguments are passed in and they are all equal
user@host:~$ bash basic-ifelse.sh 9 9 9
There are three arguments: 9, 9, and 9
9 is equal to 9 and is equal to 9
# If three arguments are passed in and the first is greater than the second
# and greater than the third
user@host:~$ bash basic-ifelse.sh 12 9 9
There are three arguments: 12, 9, and 9
12 is greater than 9 and is greater than 9
# If three arguments are passed in and the first is equal to the second
# and less than the third
user@host:~$ bash basic-ifelse.sh 12 12 40
There are three arguments: 12, 12, and 40
12 is equal to 12 and is less than 40
# If three arguments are passed in and the first is equal to the second
# and less than the third
user@host:~$ bash basic-ifelse.sh 12 12 40
There are three arguments: 12, 12, and 40
12 is equal to 12 and is less than 40
# If three arguments are passed in and the first is less than the second
# and less than the third
user@host:~$ bash basic-ifelse.sh 4 12 40
There are three arguments: 4, 12, and 40
4 is less than 12 and is less than 40
# etc etc
user@host:~$ bash basic-ifelse.sh 95 2 3
There are three arguments: 95, 2, and 3
95 is greater than 2 and is greater than 3