Shell Debugging Prompt String

$PS4 defines the prompt string of your shell, which is printed during shell debugging. It’s printed when line tracing is enabled, e.g. by calling set -x.

Links

• Bash manual
• Bash manual on “Controlling the Prompt
• POSIX specification

Examples

1
2
3
4

# Print a command's line number before executing it
PS4='[${LINENO}]+ '
set -x
echo Hello