shcompatible

Sh-compatible refers to software or scripts that are designed to be portable across POSIX-compliant shells that implement the Bourne shell standard. In practice, something described as sh-compatible aims to run under any POSIX sh, and particularly under commonly used shells such as dash, ash, or the POSIX mode of Bash. The term emphasizes adherence to the POSIX shell syntax and behavior rather than to extensions found in more feature-rich shells.

The POSIX standard defines a portable subset of shell language features, including control structures (if, case, for, while), quoting rules, variable expansions, tests, and a basic set of built-in commands. A sh-compatible script generally avoids non-POSIX constructs such as certain advanced test syntaxes, array variables, or non-POSIX arithmetic or globbing features. It commonly uses a standard shebang like #!/bin/sh, uses POSIX-compatible test or [ ... ] expressions, and sticks to portable forms of command substitution and quoting.

Practically, sh-compatibility is important for portability across Unix-like systems and in constrained environments (embedded systems, package managers, cross-distribution scripts). Some shells provide a strict posix mode to improve compatibility, and others implement sh as a separate, smaller shell (for example, dash or BusyBox sh). Developers may use tools such as shellcheck or posix-oriented linters to verify POSIX compliance and avoid shell-specific extensions.

In summary, sh-compatible denotes conformity to the POSIX shell standard, enabling broad portability of scripts and reducing reliance on non-portable features across diverse environments.