The shell colon builtin: a no‑op that fuels safety and clean scripts
The colon (:) is the shell’s built‑in null command, but it can do much more: it lets you replace multi‑line argument checks with a single ${var:?msg} line, set default values, truncate files, test file permissions, and serve as a placeholder in traps. Using : shrinks boilerplate and makes scripts easier to read and debug.