Build a check you can reuse

Goal

Your script is started with one argument, a path. Write a function that checks whether the path is a file, and use set -e so that the script prints OK: PATH for a file but prints nothing and stops with a failure status for anything else.

Example

If testdata/config.txt exists, then sh answer.sh testdata/config.txt prints:

OK: testdata/config.txt

and ends with status 0 (success).

If testdata/ghost.txt does not exist, then sh answer.sh testdata/ghost.txt prints nothing at all and ends with a non-zero status (failure).

Rules

• Edit answer.sh. The path is the first argument, $1.
• Start the script with set -e, so it stops at the first failed command.
• Define a function that checks the path with the -f test inside [ ]. A function hands back the status of its last command, so a function whose last command is a failed test counts as failed.
• Call your function with the path, then print the OK: line with printf. Do it in that order, so a failed check stops the script before anything is printed.
• Print exactly one line, OK: followed directly by the path, and only when the path is a file.
• Put double quotes around $1 everywhere you use it. A path can contain spaces.
• A folder is not a file. A folder path prints nothing and fails.
• Nothing may reach the screen when the check fails. Do not print missing or any other message.
• You do not need an else. set -e does the stopping for you.
• Do not edit any file. Your script only prints.

What you'll practice

Functions, set -e, exit statuses, the -f test, $1, and quoting.

Run it

gonomicon fetch week-1/04-05-shell-functions-and-exit-statuses
cd 04-05-shell-functions-and-exit-statuses
gonomicon test
gonomicon submit

Hints

1. A function is a named block: check() { ... }. Its status is the status of the last command inside it, and [ -f "$1" ] hands back 0 for a file and 1 otherwise.
2. Put set -e at the top. Then, if check "$1" fails, the script stops right there and the printf after it never runs.
3. set -e, then check() { [ -f "$1" ]; }, then check "$1", then printf 'OK: %s\n' "$1". Write it across several lines.