“read” a single key gives an error

Question

This simple script should read one letter:

#!/bin/bash
read -n 1 key
echo $key

But it gives the following error

read: Illegal option -n

Executed by hand read -n 1 key works though.

Answer 1

The -n option to read is a bash extension, not found in some other shells. If you got the error read: Illegal option -n, it means you didn't run the script under bash. It's most likely that you ran the script under /bin/sh, and /bin/sh is not bash but dash (the error message is the one dash produces).

To run a script under bash, start it with a shebang line #!/bin/bash, make the script file executable, and call it by name. Since you have a shebang line, the problem may be that you ran . /path/to/script instead of /path/to/script from another script running under /bin/sh.