Debian Almquist shell

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Debian Almquist shell (dash) is a POSIX-compliant Unix shell, much smaller than bash. It requires less disk space but is also less feature rich. dash is a direct descendant of the NetBSD version of the Almquist Shell (ash). It was ported to Linux by Herbert Xu in early 1997. It was renamed to dash in 2002. dash executes scripts faster than bash and depends on fewer libraries. It is believed to be more reliable in case of upgrade problems or disk failures. dash may be used as:

• shell on the installation floppy disks.
• root user shell.
• /bin/sh replacement.
• a testing environment for shell scripts to verify their compatibility with POSIX syntax.

dash is a modern replacement for ash in the Debian project, and (as of the 6.10 release) is the default /bin/sh in Ubuntu. However, the transition in Ubuntu to making dash /bin/sh has broken numerous shell scripts that relied upon Bash-specific functionality, also known as Bashisms.[1] [2] To avoid this problem, scripts should explicitly declare their use of Bashisms with the line:

#!/bin/bash

Sources

• dash home
• Debian package overview
• Ubuntu feature specification: Dash as /bin/sh