SC2006.md

Pattern: Use of legacy `STATEMENT`

Issue: -

Description

Backtick command substitution `STATEMENT` is legacy syntax with several issues.

1. It has a series of undefined behaviors related to quoting in POSIX.
2. It imposes a custom escaping mode with surprising results.
3. It's exceptionally hard to nest.

$(STATEMENT) command substitution has none of these problems, and is therefore strongly encouraged.

Example of incorrect code:

echo "Current time: `date`"

Example of correct code:

echo "Current time: $(date)"

Further Reading

• ShellCheck - SC2006
• BashFAQ - Why is $(...) preferred over ... (backticks)?