Examples are programs like sed, tr and awk. Utilities commonly implemented as shell builtins are described in this section, such as test and kill. No fixed startup files are defined, either the standard does not mention .profile. Basic Bash features Since the Bourne shell provides Bash with most of its philosophical underpinnings, Bash inherits most of its features and functionality from sh. Shell functions, introduced in the SVR2 version of the Bourne shell, are similar to shell scripts, but are defined using a special syntax and are executed in the same process as the calling shell.
Bash has shell functions which behave in a fashion upward-compatible with sh functions.
Bash implements essentially the same grammar, parameter and variable expansion semantics, redirection, and quoting as the Bourne shell. Bash includes features from the Korn Shell for both interactive use and shell programming. The typeset builtin is used to define variables and give them attributes such as readonly. Bash arithmetic allows the evaluation of an expression and the substitution of the result. Shell variables may be used as operands, and the result of an expression may be assigned to a variable.