The constructs permit fine-grained control of the input and output of those commands.Moreover, the shell allows control over the contents of commands’ environments.Shells also provide a small set of built-in commands ( builtins, among others, could be implemented in separate utilities, but they are more convenient to use as builtin commands.
The programming language features allow these utilities to be combined.
Files containing commands can be created, and become commands themselves.
These new commands have the same status as system commands in directories such as , allowing users or groups to establish custom environments to automate their common tasks.
Shells may be used interactively or non-interactively.
In interactive mode, they accept input typed from the keyboard.
When executing non-interactively, shells execute commands read from a file.A shell allows execution of commands, both synchronously and asynchronously.The shell waits for synchronous commands to complete before accepting more input; asynchronous commands continue to execute in parallel with the shell while it reads and executes additional commands.This text is a brief description of the features that are present in the Bash shell (version 4.4, 7 September 2016). This is Edition 4.4, last updated 7 September 2016, of ).The following menu breaks the features up into categories, noting which features were inspired by other shells and which are specific to Bash.This manual is meant as a brief introduction to features found in Bash.