# Optional Features (Bash Reference Manual)

The Bash `configure` has a number of --enable-feature options, where feature indicates an optional part of Bash. There are also several --with-package options, where package is something like ‘bash-malloc’ or ‘purify’. To turn off the default use of a package, use --without-package. To configure Bash without a feature that is enabled by default, use --disable-feature.

Here is a complete list of the --enable- and --with- options that the Bash `configure` recognizes.`--with-afs`

Define if you are using the Andrew File System from Transarc.`--with-bash-malloc`

Use the Bash version of `malloc` in the directory lib/malloc. This is not the same `malloc` that appears in GNU libc, but an older version originally derived from the 4.2 BSD `malloc`. This `malloc` is very fast, but wastes some space on each allocation. This option is enabled by default. The NOTES file contains a list of systems for which this should be turned off, and `configure` disables this option automatically for a number of systems.`--with-curses`

Use the curses library instead of the termcap library. This should be supplied if your system has an inadequate or incomplete termcap database.`--with-gnu-malloc`

A synonym for `--with-bash-malloc`.`--with-installed-readline[=PREFIX]`

Define this to make Bash link with a locally-installed version of Readline rather than the version in lib/readline. This works only with Readline 5.0 and later versions. If PREFIX is `yes` or not supplied, `configure` uses the values of the make variables `includedir` and `libdir`, which are subdirectories of `prefix` by default, to find the installed version of Readline if it is not in the standard system include and library directories. If PREFIX is `no`, Bash links with the version in lib/readline. If PREFIX is set to any other value, `configure` treats it as a directory pathname and looks for the installed version of Readline in subdirectories of that directory (include files in PREFIX/`include` and the library in PREFIX/`lib`).`--with-purify`

Define this to use the Purify memory allocation checker from Rational Software.`--enable-minimal-config`

This produces a shell with minimal features, close to the historical Bourne shell.

There are several --enable- options that alter how Bash is compiled and linked, rather than changing run-time features.

The ‘minimal-config’ option can be used to disable all of the following options, but it is processed first, so individual options may be enabled using ‘enable-feature’.

All of the following options except for ‘disabled-builtins’, ‘direxpand-default’, and ‘xpg-echo-default’ are enabled by default, unless the operating system does not provide the necessary support.`--enable-alias`

Allow alias expansion and include the `alias` and `unalias` builtins (see [Aliases](https://woodrowpearson.gitbook.io/code-gists/aliases-bash-reference-manual#Aliases)).`--enable-arith-for-command`

Include support for the alternate form of the `for` command that behaves like the C language `for` statement (see [Looping Constructs](https://woodrowpearson.gitbook.io/code-gists/looping-constructs-bash-reference-manual#Looping-Constructs)).`--enable-array-variables`

Include support for one-dimensional array shell variables (see [Arrays](https://woodrowpearson.gitbook.io/code-gists/arrays-bash-reference-manual#Arrays)).`--enable-bang-history`

Include support for `csh`-like history substitution (see [History Interaction](https://woodrowpearson.gitbook.io/code-gists/history-interaction-bash-reference-manual#History-Interaction)).`--enable-brace-expansion`

Include `csh`-like brace expansion ( `b{a,b}c` → `bac bbc` ). See [Brace Expansion](https://woodrowpearson.gitbook.io/code-gists/brace-expansion-bash-reference-manual#Brace-Expansion), for a complete description.`--enable-casemod-attributes`

Include support for case-modifying attributes in the `declare` builtin and assignment statements. Variables with the uppercase attribute, for example, will have their values converted to uppercase upon assignment.`--enable-casemod-expansion`

Include support for case-modifying word expansions.`--enable-command-timing`

Include support for recognizing `time` as a reserved word and for displaying timing statistics for the pipeline following `time` (see [Pipelines](https://woodrowpearson.gitbook.io/code-gists/pipelines-bash-reference-manual#Pipelines)). This allows pipelines as well as shell builtins and functions to be timed.`--enable-cond-command`

Include support for the `[[` conditional command. (see [Conditional Constructs](https://woodrowpearson.gitbook.io/code-gists/conditional-constructs-bash-reference-manual#Conditional-Constructs)).`--enable-cond-regexp`

Include support for matching POSIX regular expressions using the ‘=\~’ binary operator in the `[[` conditional command. (see [Conditional Constructs](https://woodrowpearson.gitbook.io/code-gists/conditional-constructs-bash-reference-manual#Conditional-Constructs)).`--enable-coprocesses`

Include support for coprocesses and the `coproc` reserved word (see [Pipelines](https://woodrowpearson.gitbook.io/code-gists/pipelines-bash-reference-manual#Pipelines)).`--enable-debugger`

Include support for the bash debugger (distributed separately).`--enable-dev-fd-stat-broken`

If calling `stat` on /dev/fd/N returns different results than calling `fstat` on file descriptor N, supply this option to enable a workaround. This has implications for conditional commands that test file attributes.`--enable-direxpand-default`

Cause the `direxpand` shell option (see [The Shopt Builtin](https://woodrowpearson.gitbook.io/code-gists/the-shopt-builtin-bash-reference-manual#The-Shopt-Builtin)) to be enabled by default when the shell starts. It is normally disabled by default.`--enable-directory-stack`

Include support for a `csh`-like directory stack and the `pushd`, `popd`, and `dirs` builtins (see [The Directory Stack](https://woodrowpearson.gitbook.io/code-gists/the-directory-stack-bash-reference-manual#The-Directory-Stack)).`--enable-disabled-builtins`

Allow builtin commands to be invoked via ‘builtin xxx’ even after `xxx` has been disabled using ‘enable -n xxx’. See [Bash Builtins](https://woodrowpearson.gitbook.io/code-gists/bash-builtins-bash-reference-manual#Bash-Builtins), for details of the `builtin` and `enable` builtin commands.`--enable-dparen-arithmetic`

Include support for the `((…))` command (see [Conditional Constructs](https://woodrowpearson.gitbook.io/code-gists/conditional-constructs-bash-reference-manual#Conditional-Constructs)).`--enable-extended-glob`

Include support for the extended pattern matching features described above under [Pattern Matching](https://woodrowpearson.gitbook.io/code-gists/pattern-matching-bash-reference-manual#Pattern-Matching).`--enable-extended-glob-default`

Set the default value of the extglob shell option described above under [The Shopt Builtin](https://woodrowpearson.gitbook.io/code-gists/the-shopt-builtin-bash-reference-manual#The-Shopt-Builtin) to be enabled.`--enable-function-import`

Include support for importing function definitions exported by another instance of the shell from the environment. This option is enabled by default.`--enable-glob-asciirange-default`

Set the default value of the globasciiranges shell option described above under [The Shopt Builtin](https://woodrowpearson.gitbook.io/code-gists/the-shopt-builtin-bash-reference-manual#The-Shopt-Builtin) to be enabled. This controls the behavior of character ranges when used in pattern matching bracket expressions.`--enable-help-builtin`

Include the `help` builtin, which displays help on shell builtins and variables (see [Bash Builtins](https://woodrowpearson.gitbook.io/code-gists/bash-builtins-bash-reference-manual#Bash-Builtins)).`--enable-history`

Include command history and the `fc` and `history` builtin commands (see [Bash History Facilities](https://woodrowpearson.gitbook.io/code-gists/bash-history-facilities-bash-reference-manual#Bash-History-Facilities)).`--enable-job-control`

This enables the job control features (see [Job Control](https://woodrowpearson.gitbook.io/code-gists/job-control-bash-reference-manual#Job-Control)), if the operating system supports them.`--enable-multibyte`

This enables support for multibyte characters if the operating system provides the necessary support.`--enable-net-redirections`

This enables the special handling of filenames of the form `/dev/tcp/host/port` and `/dev/udp/host/port` when used in redirections (see [Redirections](https://woodrowpearson.gitbook.io/code-gists/redirections-bash-reference-manual#Redirections)).`--enable-process-substitution`

This enables process substitution (see [Process Substitution](https://woodrowpearson.gitbook.io/code-gists/process-substitution-bash-reference-manual#Process-Substitution)) if the operating system provides the necessary support.`--enable-progcomp`

Enable the programmable completion facilities (see [Programmable Completion](https://woodrowpearson.gitbook.io/code-gists/programmable-completion-bash-reference-manual#Programmable-Completion)). If Readline is not enabled, this option has no effect.`--enable-prompt-string-decoding`

Turn on the interpretation of a number of backslash-escaped characters in the `$PS0`, `$PS1`, `$PS2`, and `$PS4` prompt strings. See [Controlling the Prompt](https://woodrowpearson.gitbook.io/code-gists/controlling-the-prompt-bash-reference-manual#Controlling-the-Prompt), for a complete list of prompt string escape sequences.`--enable-readline`

Include support for command-line editing and history with the Bash version of the Readline library (see [Command Line Editing](https://woodrowpearson.gitbook.io/code-gists/command-line-editing-bash-reference-manual#Command-Line-Editing)).`--enable-restricted`

Include support for a *restricted shell*. If this is enabled, Bash, when called as `rbash`, enters a restricted mode. See [The Restricted Shell](https://woodrowpearson.gitbook.io/code-gists/the-restricted-shell-bash-reference-manual#The-Restricted-Shell), for a description of restricted mode.`--enable-select`

Include the `select` compound command, which allows the generation of simple menus (see [Conditional Constructs](https://woodrowpearson.gitbook.io/code-gists/conditional-constructs-bash-reference-manual#Conditional-Constructs)).`--enable-separate-helpfiles`

Use external files for the documentation displayed by the `help` builtin instead of storing the text internally.`--enable-single-help-strings`

Store the text displayed by the `help` builtin as a single string for each help topic. This aids in translating the text to different languages. You may need to disable this if your compiler cannot handle very long string literals.`--enable-strict-posix-default`

Make Bash POSIX-conformant by default (see [Bash POSIX Mode](https://woodrowpearson.gitbook.io/code-gists/bash-posix-mode-bash-reference-manual#Bash-POSIX-Mode)).`--enable-usg-echo-default`

A synonym for `--enable-xpg-echo-default`.`--enable-xpg-echo-default`

Make the `echo` builtin expand backslash-escaped characters by default, without requiring the -e option. This sets the default value of the `xpg_echo` shell option to `on`, which makes the Bash `echo` behave more like the version specified in the Single Unix Specification, version 3. See [Bash Builtins](https://woodrowpearson.gitbook.io/code-gists/bash-builtins-bash-reference-manual#Bash-Builtins), for a description of the escape sequences that `echo` recognizes.

The file config-top.h contains C Preprocessor ‘#define’ statements for options which are not settable from `configure`. Some of these are not meant to be changed; beware of the consequences if you do. Read the comments associated with each definition for more information about its effect.