How can we delete space with a shell script? - bash

Question

I did a script in order to display different things, in different case.
The script is :
#!/usr/bin/env bash
# declare an array, to store stuff in
declare -a myArray
shopt -s nocasematch
# read the full file into the array
# This while loop terminates when pressing CTRL-D
i=1
while read -r line; do
myArray[i]="${line}"
((i++))
done < /dev/stdin
# Process the array
for ((j=1;j<i;++j)); do
# perform your actions here on myArray[j]
case "${myArray[j]}" in
bob)
echo "boy"
;;
alicia)
echo "girl"
;;
cookie)
echo "dog"
;;
*)
echo "unknown" "${myArray[j]}"
;;
esac
done
But I have a problem, when I execute the code with this command:
cat input.txt | ./prog.sh > file.txt
I have the following input:
bob
alicia
amhed
cookie
daniel
In this input I have so space, but when I run my program I don't obtain this right result. I need my code not to take into account spaces, but if it take care about the space, is wrote "unknown" on the OUTPOUT file.txt
and I obtain the result :
boy
girl
unknown amhed
dog
unknown
unknown
unknown daniel
So can I eliminate/delete the space without touching the input file?

Answer 1

why do this in bash?
with awk
$ awk 'BEGIN{n=split("bob boy alicia girl cookie dog",x);
for(i=1;i<n;i+=2) a[x[i]]=x[i+1]} # build the lookup table
{print $1 in a?a[$1]:"unknown "$1}' file
boy
girl
unknown amhed
dog
unknown
unknown
unknown daniel
you can externalize the lookup map to another file as well, so that the code doesn't need to be modified if either values change.

Answer 2

If you want to do nothing when the input line is empty, you can add that to your case:
#!/usr/bin/env bash
# declare an array, to store stuff in
declare -a myArray
shopt -s nocasematch
# read the full file into the array
# This while loop terminates when pressing CTRL-D
i=1
while read -r line; do
myArray[i]="${line}"
((i++))
done < /dev/stdin
# Process the array
for ((j=1;j<i;++j)); do
# perform your actions here on myArray[j]
case "${myArray[j]}" in
"") # This is an empty line, skip it
;;
bob)
echo "boy"
;;
alicia)
echo "girl"
;;
cookie)
echo "dog"
;;
*)
echo "unknown" "${myArray[j]}"
;;
esac
done
Alternatively, check whether the line you read was empty before adding it to the array.

Answer 3

You can read from stdin and process each line and avoid array creation.
Use && [[ -n $line ]] to make sure you process only non-empty lines.
By default read command reads it from /dev/stdin so you can omit < /dev/stdin from your code.
Code:
shopt -s nocasematch
while read -r line && [[ -n $line ]]; do
case "$line" in
bob)
echo "boy"
;;
alicia)
echo "girl"
;;
cookie)
echo "dog"
;;
*)
echo "unknown $line"
;;
esac
done
Run it as:
./prog.sh < input.txt
Output:
boy
girl
unknown amhed
dog