Issue with running a shell script without using 'sh' on macOS Monterey

Question

I'm new to shell scripting and generally the usage of Terminal. I recently made a script.sh that I want to use by just typing its name without the full path. So, I wrote the path of the directory into .zprofile as:

export "PATH=$PATH:/path/to/scriptdirectory"

and changed the file permissions with:

% chmod +x script.sh

If I use the script with:

% sh myscript.sh

everything run smoothly as intended. But if I try to omit the sh and type:

% myscript.sh

the script start running its first part, which is just reading a variable, but as soon as I insert the value, the follow line pops:

/path/to/scriptdirectory/script.sh:11: = not found

This is the script:

#!/bin/zsh
echo "Do you want to set or change the backup location? (type y/n)"
read SET_BACKUP
while [ "$SET_BACKUP" != "y" ] && [ "$SET_BACKUP" != "n" ]
do
    echo "Please, write y or n:"
    read SET_BACKUP
done
if [ "$SET_BACKUP" == "y" ]
then
    echo "Write the absolute path of the desired backup location:"
    read BACKUP_FOLDER
    echo "Starting backup..."
    cp -R "/fileslocation" "$BACKUP_FOLDER"
    echo "Backup completed."
else
    echo "Starting backup..."
    cp -R "/fileslocation" "$BACKUP_FOLDER"
    echo "Backup completed."
fi

Answer 1

The difference is that you're running the script with two different shell interpreters.

When you use sh myscript.sh, you're running /bin/sh and not zsh. When sh runs it reads your script myscript.sh and uses sh/bash shell rules for its syntax.

When you use just myscript.sh, the command used to run the script is determined by the first line: #!/bin/zsh (also known as the shebang). So it's run using zsh and uses its rules for syntax.

I see two solutions to get this working:

1. change the first line to use bash instead, so it'd be #!/bin/bash
2. read more about how conditionals work in zsh and fix the line that's broken (it looks like it's the line with if [ "$SET_BACKUP" == "y" ])

Answer 2

This is not really an answer, more of a formatted question.

3 things come to mind:

1. variable assignments must not have spaces around the =: answer=42
2. $ is only used to de-reference a variable, not to assign: don't do $answer=42
3. quote your variables: if [ "$answer" = 42 ]

This is me trying to read your mind. Put some code in your question.

Also, use https://shellcheck.net to validate your shell code.