### Simulate Installation with DESTDIR

Source: https://www.gnu.org/software/bash/manual/html_node/Installation-Names.html

Use the 'DESTDIR' variable with 'make install' to simulate an installation and preview file locations without modifying the system. The value of DESTDIR acts as the root for the sample installation tree.

```bash
mkdir /fs1/bash-install
make install DESTDIR=/fs1/bash-install
```

--------------------------------

### Specify Installation Prefixes for a Single Run

Source: https://www.gnu.org/software/bash/manual/html_node/Installation-Names.html

Override installation locations for a single 'make install' run by specifying variables like 'exec_prefix' as arguments to make.

```bash
make install exec_prefix=/
```

--------------------------------

### Install compiled MO files

Source: https://www.gnu.org/software/bash/manual/html_node/Creating-Internationalized-Scripts.html

Install the compiled MO files into the appropriate directory structure. This involves setting `TEXTDOMAIN` and `TEXTDOMAINDIR` and copying the MO files to their final locations.

```bash
TEXTDOMAIN=example
TEXTDOMAINDIR=/usr/local/share/locale

cp es.mo ${TEXTDOMAINDIR}/es/LC_MESSAGES/${TEXTDOMAIN}.mo
cp eo.mo ${TEXTDOMAINDIR}/eo/LC_MESSAGES/${TEXTDOMAIN}.mo
```

--------------------------------

### Specify Installation Prefix with make

Source: https://www.gnu.org/software/bash/manual/html_node/Installation-Names.html

Use the 'prefix' make variable to specify a custom installation prefix other than the default /usr/local.

```bash
make install prefix=/path/to/install
```

--------------------------------

### AND List Example

Source: https://www.gnu.org/software/bash/manual/html_node/Lists.html

Execute command2 if and only if command1 returns a zero exit status (success).

```bash
command1 && command2

```

--------------------------------

### Bash select Statement Example

Source: https://www.gnu.org/software/bash/manual/html_node/Conditional-Constructs.html

An example of the select statement that allows the user to pick a filename from the current directory and displays the selection.

```bash
select fname in *;
do
	echo you picked $fname \($REPLY\)
	break;
done

```

--------------------------------

### Install Bash Completion Function for `cd`

Source: https://www.gnu.org/software/bash/manual/html_node/A-Programmable-Completion-Example.html

This command installs the `_comp_cd` function as the completion handler for the `cd` builtin. It uses options to control filename handling, quoting, and default Bash completions.

```bash
# Tell readline to quote appropriate and append slashes to directories;
# use the bash default completion for other arguments
complete -o filenames -o nospace -o bashdefault -F _comp_cd cd

```

--------------------------------

### Specify Separate Prefixes for Executable and Data Files

Source: https://www.gnu.org/software/bash/manual/html_node/Installation-Names.html

Use the '--exec-prefix' option with configure to set a separate installation prefix for programs and libraries, while documentation and data files use the regular prefix.

```bash
configure --exec-prefix=/path/to/executables
```

--------------------------------

### Sample inputrc Configuration

Source: https://www.gnu.org/software/bash/manual/html_node/Sample-Init-File.html

This is a comprehensive example of an inputrc file. It shows how to include system-wide settings, configure emacs editing mode, bind keys for emacs and default modes, and define application-specific macros for Bash and FTP. It also demonstrates setting various Readline variables.

```inputrc
# This file controls the behavior of line input editing for
# programs that use the GNU Readline library.  Existing
# programs include FTP, Bash, and GDB.
#
# You can re-read the inputrc file with C-x C-r.
# Lines beginning with '#' are comments.
#
# First, include any system-wide bindings and variable
# assignments from /etc/Inputrc
$include /etc/Inputrc

#
# Set various bindings for emacs mode.

set editing-mode emacs 

$if mode=emacs

Meta-Control-h:	backward-kill-word	Text after the function name is ignored

#
# Arrow keys in keypad mode
#
#"\M-OD":        backward-char
#"\M-OC":        forward-char
#"\M-OA":        previous-history
#"\M-OB":        next-history
#
# Arrow keys in ANSI mode
#
"\M-[D":        backward-char
"\M-[C":        forward-char
"\M-[A":        previous-history
"\M-[B":        next-history
#
# Arrow keys in 8 bit keypad mode
#
#"\M-\C-OD":       backward-char
#"\M-\C-OC":       forward-char
#"\M-\C-OA":       previous-history
#"\M-\C-OB":       next-history
#
# Arrow keys in 8 bit ANSI mode
#
#"\M-\C-[D":       backward-char
#"\M-\C-[C":       forward-char
#"\M-\C-[A":       previous-history
#"\M-\C-[B":       next-history

C-q: quoted-insert

$endif

# An old-style binding.  This happens to be the default.
TAB: complete

# Macros that are convenient for shell interaction
$if Bash
# edit the path
"\C-xp": "PATH=${PATH}\e\C-e\C-a\ef\C-f"
# prepare to type a quoted word --
# insert open and close double quotes
# and move to just after the open quote
"\C-x\"": ""\C-b"
# insert a backslash (testing backslash escapes
# in sequences and macros)
"\C-x\\": "\\"
# Quote the current or previous word
"\C-xq": "\eb"\ef""
# Add a binding to refresh the line, which is unbound
"\C-xr": redraw-current-line
# Edit variable on current line.
"\M-\C-v": "\C-a\C-k$\C-y\M-\C-e\C-a\C-y="
$endif

# use a visible bell if one is available
set bell-style visible

# don't strip characters to 7 bits when reading
set input-meta on

# allow iso-latin1 characters to be inserted rather
# than converted to prefix-meta sequences
set convert-meta off

# display characters with the eighth bit set directly
# rather than as meta-prefixed characters
set output-meta on

# if there are 150 or more possible completions for a word, 
# ask whether or not the user wants to see all of them
set completion-query-items 150

# For FTP
$if Ftp
"\C-xg": "get \M-?"
"\C-xt": "put \M-?"
"\M-.": yank-last-arg
$endif

```

--------------------------------

### OR List Example

Source: https://www.gnu.org/software/bash/manual/html_node/Lists.html

Execute command2 if and only if command1 returns a non-zero exit status (failure).

```bash
command1 || command2

```

--------------------------------

### Bash case Statement Example

Source: https://www.gnu.org/software/bash/manual/html_node/Conditional-Constructs.html

An example demonstrating the use of the case statement to describe an animal based on user input. It uses a default '*' pattern.

```bash
echo -n "Enter the name of an animal: "
read ANIMAL
echo -n "The $ANIMAL has "
case $ANIMAL in
  horse | dog | cat) echo -n "four";;
  man | kangaroo ) echo -n "two";;
  *) echo -n "an unknown number of";;
esac
echo " legs."

```

--------------------------------

### Bash Job Notification Example

Source: https://www.gnu.org/software/bash/manual/html_node/Job-Control-Basics.html

This is an example of the notification Bash displays when a job starts asynchronously. It indicates the job number and the process ID of the last process in the pipeline.

```bash
[1] 25647

```

--------------------------------

### Bash 'set -P' Symbolic Link Handling Example

Source: https://www.gnu.org/software/bash/manual/html_node/The-Set-Builtin.html

Demonstrates how 'set -P' prevents Bash from resolving symbolic links when changing directories, affecting the reported PWD.

```bash
$ cd /usr/sys; echo $PWD
/usr/sys
$ cd ..; pwd
/usr


```

```bash
If `set -P` is on, then: 
$ cd /usr/sys; echo $PWD
/usr/local/sys
$ cd ..; pwd
/usr/local

```

--------------------------------

### Display Configure Script Help

Source: https://www.gnu.org/software/bash/manual/html_node/Basic-Installation.html

View available options for the configure script to customize the build process.

```bash
bash-4.2$ ./configure --help

```

--------------------------------

### Bash Regex Match Anchored at Start

Source: https://www.gnu.org/software/bash/manual/html_node/Conditional-Constructs.html

This example demonstrates matching a literal string at the beginning of a line using regular expressions within Bash. Quoting the pattern correctly is crucial for the anchor character `^` to be interpreted as a regex operator.

```bash
[[ $line =~ ^"initial string" ]]
```

--------------------------------

### Getting the Number of Elements in an Array

Source: https://www.gnu.org/software/bash/manual/html_node/Arrays.html

Get the total number of elements in an array by using the '#' operator with the '@' or '*' subscript.

```bash
${#name[@]}
```

```bash
${#name[*]}
```

--------------------------------

### Getting the Length of an Array Element

Source: https://www.gnu.org/software/bash/manual/html_node/Arrays.html

Get the length of a specific array element by using the '#' operator before the array expansion.

```bash
${#name[subscript]}
```

--------------------------------

### Create Build Tree with mkclone

Source: https://www.gnu.org/software/bash/manual/html_node/Compiling-For-Multiple-Architectures.html

Use the `mkclone` script to create a build directory with symbolic links to source files. This method requires Bash to be already built for at least one architecture.

```bash
bash /usr/gnu/src/bash-2.0/support/mkclone -s /usr/gnu/src/bash-2.0 .
```

--------------------------------

### Display 'set' Commands for Current Options

Source: https://www.gnu.org/software/bash/manual/html_node/The-Set-Builtin.html

Demonstrates how to print a series of 'set' commands that would recreate the current option settings by using 'set +o' without any specific option name.

```bash
set +o
```

--------------------------------

### Bash Long Option: --help

Source: https://www.gnu.org/software/bash/manual/html_node/Invoking-Bash.html

Displays a usage message on standard output and exits.

```bash
--help
```

--------------------------------

### Create gettext template file

Source: https://www.gnu.org/software/bash/manual/html_node/Creating-Internationalized-Scripts.html

Generate a template file (.pot) from your script to extract translatable strings. This file serves as the basis for creating translations.

```bash
bash --dump-po-strings scriptname > domain.pot
```

--------------------------------

### Alternative Coprocess Forms

Source: https://www.gnu.org/software/bash/manual/html_node/Coprocesses.html

Demonstrates other valid syntaxes for coprocesses, including variations with and without a NAME.

```bash
coproc NAME compound-command
coproc compound-command
coproc simple-command

```

--------------------------------

### Get Parameter Attributes

Source: https://www.gnu.org/software/bash/manual/html_node/Shell-Parameter-Expansion.html

Returns a string consisting of flag values representing the parameter's attributes.

```shell
${parameter@a}
```

--------------------------------

### Bash Long Option: --init-file

Source: https://www.gnu.org/software/bash/manual/html_node/Invoking-Bash.html

Specifies a file to execute commands from instead of ~/.bashrc in an interactive shell.

```bash
--init-file filename
```

--------------------------------

### Set Editing Mode to Vi

Source: https://www.gnu.org/software/bash/manual/html_node/Readline-Init-File-Syntax.html

Example of setting the Readline editing mode to 'vi' for line editing commands.

```bash
set editing-mode vi
```

--------------------------------

### Bash Long Option: --debugger

Source: https://www.gnu.org/software/bash/manual/html_node/Invoking-Bash.html

Enables extended debugging mode by executing the debugger profile before the shell starts.

```bash
--debugger
```

--------------------------------

### Select Second Argument of Matching Command

Source: https://www.gnu.org/software/bash/manual/html_node/Word-Designators.html

The `!fi:2` syntax selects the second argument (word 2) of the most recent command starting with 'fi'.

```bash
!fi:2
    
designates the second argument of the most recent command starting with the letters `fi`.
```

--------------------------------

### Bind: Display Reusable Bindings

Source: https://www.gnu.org/software/bash/manual/html_node/Bash-Builtins.html

The '-p' option displays current Readline bindings in a format suitable for input to 'bind' or a Readline initialization file.

```bash
bind -p
```

--------------------------------

### Recommended Coprocess Form

Source: https://www.gnu.org/software/bash/manual/html_node/Coprocesses.html

This form is preferred for its simplicity and completeness, especially when dealing with compound commands.

```bash
coproc NAME { command; }

```

--------------------------------

### Exporting a Variable with Assignment

Source: https://www.gnu.org/software/bash/manual/html_node/Shell-Parameters.html

Shows how to use the 'command export' built-in to assign a value to a variable and export it. This is an example of an assignment statement used with a declaration command.

```shell
command export var=value
```

--------------------------------

### Bash 'set --' Assigning Positional Parameters

Source: https://www.gnu.org/software/bash/manual/html_node/The-Set-Builtin.html

Shows how '--' can be used to unset positional parameters or assign remaining arguments to them, even if they start with a hyphen.

```bash
The remaining N arguments are positional parameters and are assigned, in order, to `$1`, `$2`, … `$N`. The special parameter `#` is set to N.
```

--------------------------------

### Shopt Builtin Syntax

Source: https://www.gnu.org/software/bash/manual/html_node/The-Shopt-Builtin.html

Displays the general syntax for using the 'shopt' builtin command. It can be used with various options to manage shell behavior settings.

```bash
shopt [-pqsu] [-o] [optname ...]
```

--------------------------------

### Set Active Region Start Color

Source: https://www.gnu.org/software/bash/manual/html_node/Readline-Init-File-Syntax.html

Controls the text color and background for the active region using terminal escape sequences. This variable is reset when the terminal type changes.

```bash
set active-region-start-color "\e[01;33m"
```

--------------------------------

### Bash read command usage

Source: https://www.gnu.org/software/bash/manual/html_node/Bash-Builtins.html

Demonstrates the basic syntax and options for the `read` builtin command to capture user input.

```bash
read [-Eers] [-a aname] [-d delim] [-i text] [-n nchars]
    [-N nchars] [-p prompt] [-t timeout] [-u fd] [name ...]
```

--------------------------------

### Basic Pipeline Syntax

Source: https://www.gnu.org/software/bash/manual/html_node/Pipelines.html

Illustrates the fundamental structure of a Bash pipeline, connecting commands with '|' or '|&'.

```bash
[time [-p]] [!] command1 [ | or |& command2 ] ...

```

--------------------------------

### Non-interactive Script Execution with BASH_ENV

Source: https://www.gnu.org/software/bash/manual/html_node/Bash-Startup-Files.html

When Bash is invoked non-interactively to run a script, it checks for the BASH_ENV variable and sources the specified file if it is set. This allows for environment setup for scripts.

```bash
if [ -n "$BASH_ENV" ]; then . "$BASH_ENV"; fi
```

--------------------------------

### Assigning Values to an Indexed Array

Source: https://www.gnu.org/software/bash/manual/html_node/Arrays.html

Assign multiple values to an indexed array using compound assignment. Elements are assigned sequentially starting from index 0 unless a specific index is provided.

```bash
name=(value1 value2 ... )
```

--------------------------------

### Bash help command syntax

Source: https://www.gnu.org/software/bash/manual/html_node/Bash-Builtins.html

Displays helpful information about builtin commands. It can show detailed help for matching patterns or a list of all builtins.

```bash
help [-dms] [pattern]

```

--------------------------------

### Basic Coprocess Syntax

Source: https://www.gnu.org/software/bash/manual/html_node/Coprocesses.html

The fundamental syntax for initiating a coprocess. NAME is optional and defaults to COPROC if not provided.

```bash
coproc [NAME] command [redirections]

```

--------------------------------

### Specifying Bash Interpreter with Shebang

Source: https://www.gnu.org/software/bash/manual/html_node/Shell-Scripts.html

This is a common idiom to ensure Bash interprets the script, even if installed in a different directory. It uses 'env' to find the first occurrence of 'bash' in the system's PATH.

```shell
#! /bin/bash
```

```shell
#!/usr/bin/env bash
```

--------------------------------

### Bash ulimit command syntax

Source: https://www.gnu.org/software/bash/manual/html_node/Bash-Builtins.html

Shows the general syntax for the ulimit builtin command. Use this command to control resource limits.

```bash
ulimit [-H | -S] [-a] [-c | -d | -f | -l | -m | -n | -p | -t | -u | -v | -x] [limit]
```

--------------------------------

### Bash Long Option: --version

Source: https://www.gnu.org/software/bash/manual/html_node/Invoking-Bash.html

Displays version information for the current Bash instance and exits.

```bash
--version
```

--------------------------------

### Substring Expansion on Positional Parameters with Offset and Length

Source: https://www.gnu.org/software/bash/manual/html_node/Shell-Parameter-Expansion.html

Extracts a specified number of positional parameters starting from a given offset. Negative offsets count from the end. A length of 0 results in no parameters being output.

```shell
$ set -- 1 2 3 4 5 6 7 8 9 0 a b c d e f g h
$ echo ${@:7}
7 8 9 0 a b c d e f g h
```

```shell
$ echo ${@:7:0}


```

```shell
$ echo ${@:7:2}
7 8
```

```shell
$ echo ${@:7:-2}
bash: -2: substring expression < 0
```

```shell
$ echo ${@: -7:2}
b c
```

```shell
$ echo ${@:0}
./bash 1 2 3 4 5 6 7 8 9 0 a b c d e f g h
```

```shell
$ echo ${@:0:2}
./bash 1
```

```shell
$ echo ${@: -7:0}


```

--------------------------------

### compgen command syntax

Source: https://www.gnu.org/software/bash/manual/html_node/Programmable-Completion-Builtins.html

Shows the general syntax for the `compgen` builtin. This command generates possible completion matches for a given word.

```bash
compgen [-V varname] [option] [word]

```

--------------------------------

### Substring Expansion on Positional Parameters

Source: https://www.gnu.org/software/bash/manual/html_node/Shell-Parameter-Expansion.html

Extracts substrings from positional parameters using offset and length. Indexing starts at 1 by default. `$0` is prefixed if offset is 0. Negative offsets count from the end.

```shell
$ set -- 01234567890abcdefgh
$ echo ${1:7}
7890abcdefgh
```

```shell
$ echo ${1:7:0}


```

```shell
$ echo ${1:7:2}
78
```

```shell
$ echo ${1:7:-2}
7890abcdef
```

```shell
$ echo ${1: -7}
bcdefgh
```

```shell
$ echo ${1: -7:0}


```

```shell
$ echo ${1: -7:2}
bc
```

```shell
$ echo ${1: -7:-2}
bcdef
```

--------------------------------

### Get Caller Subroutine Context

Source: https://www.gnu.org/software/bash/manual/html_node/Bash-Builtins.html

The `caller` command returns the context of an active subroutine call. Without arguments, it shows the current line and filename; with an integer argument, it shows details for that frame in the call stack.

```bash
caller [expr]
```

--------------------------------

### Executing a Shell Script

Source: https://www.gnu.org/software/bash/manual/html_node/Shell-Scripts.html

This demonstrates the equivalent ways to execute a shell script. The first is by directly calling the script file, and the second is by explicitly invoking the bash interpreter.

```shell
filename arguments
```

```shell
bash filename arguments
```

--------------------------------

### Substring Expansion on Indexed Arrays with Offset and Length

Source: https://www.gnu.org/software/bash/manual/html_node/Shell-Parameter-Expansion.html

Extracts a specified number of elements from an indexed array starting from a given offset. Negative offsets count from the end. A length of 0 results in no elements being output.

```shell
$ array=(0 1 2 3 4 5 6 7 8 9 0 a b c d e f g h)
$ echo ${array[@]:7}
7 8 9 0 a b c d e f g h
```

```shell
$ echo ${array[@]:7:2}
7 8
```

```shell
$ echo ${array[@]: -7:2}
b c
```

```shell
$ echo ${array[@]: -7:-2}
bash: -2: substring expression < 0
```

```shell
$ echo ${array[@]:0}
0 1 2 3 4 5 6 7 8 9 0 a b c d e f g h
```

```shell
$ echo ${array[@]:0:2}
0 1
```

```shell
$ echo ${array[@]: -7:0}


```

--------------------------------

### Bind: Execute Readline Command Line

Source: https://www.gnu.org/software/bash/manual/html_node/Bash-Builtins.html

A raw readline command line can be passed directly to 'bind' for execution.

```bash
bind readline-command-line
```

--------------------------------

### Basic Brace Expansion with Comma-Separated Strings

Source: https://www.gnu.org/software/bash/manual/html_node/Brace-Expansion.html

Demonstrates generating strings by expanding a comma-separated list within braces, with a common prefix and suffix. Brace expansion is performed before other expansions.

```bash
echo a{d,c,b}e
```

--------------------------------

### Bash Character Class Example

Source: https://www.gnu.org/software/bash/manual/html_node/Pattern-Matching.html

This pattern matches a whitespace character, followed by an uppercase letter or an exclamation mark, then a dot, and finally a lowercase letter or a hyphen. Ensure the 'extglob' shell option is enabled for extended pattern matching.

```bash
[[:space:]][[:upper:]!].[-[:lower:]]
```

--------------------------------

### Bash Regex Match with Quoted Anchor (Incorrect)

Source: https://www.gnu.org/software/bash/manual/html_node/Conditional-Constructs.html

Illustrates an incorrect way to match a string at the start of a line using regex in Bash. Quoting the `^` character prevents it from being interpreted as a regular expression anchor, causing it to be matched literally.

```bash
[[ $line =~ "^initial string" ]]
```

--------------------------------

### complete command syntax

Source: https://www.gnu.org/software/bash/manual/html_node/Programmable-Completion-Builtins.html

Displays the syntax for the `complete` builtin, used to specify how arguments to commands should be completed.

```bash
complete [-abcdefgjksuv] [-o comp-option] [-DEI] [-A action]
[-G globpat] [-W wordlist] [-F function] [-C command]
[-X filterpat] [-P prefix] [-S suffix] name [name ...]

```

```bash
complete -pr [-DEI] [name ...]

```

--------------------------------

### Bash Regex Matching with Backslashes and Quotes

Source: https://www.gnu.org/software/bash/manual/html_node/Conditional-Constructs.html

Demonstrates how backslashes and quoting affect regular expression matching in Bash's `[[ ... =~ ... ]]` construct. The first two examples match a literal dot, while the latter two do not due to quoting.

```bash
pattern='\\.'

[[ . =~ $pattern ]]
[[ . =~ \\. ]]

[[ . =~ "$pattern" ]]
[[ . =~ '\\.' ]]
```

--------------------------------

### Bind: Display Key Sequences for Function

Source: https://www.gnu.org/software/bash/manual/html_node/Bash-Builtins.html

Use the '-q' option to display the key sequences that invoke a named Readline function.

```bash
bind -q function
```

--------------------------------

### Creating Directories with Brace Expansion

Source: https://www.gnu.org/software/bash/manual/html_node/Brace-Expansion.html

Uses brace expansion to create multiple directories with a common path and varying subdirectories. This is a common shorthand for repetitive directory creation.

```bash
mkdir /usr/local/src/bash/{old,new,dist,bugs}
```

--------------------------------

### Include External Readline Configuration File

Source: https://www.gnu.org/software/bash/manual/html_node/Conditional-Init-Constructs.html

Includes commands and key bindings from an external file, such as '/etc/inputrc'. This is useful for modular configuration.

```bash
$include /etc/inputrc

```

--------------------------------

### Bash read command with prompt

Source: https://www.gnu.org/software/bash/manual/html_node/Bash-Builtins.html

Demonstrates displaying a prompt before reading input using the `-p` option.

```bash
read -p prompt
```

--------------------------------

### Bind: List Readline Functions

Source: https://www.gnu.org/software/bash/manual/html_node/Bash-Builtins.html

Use the '-l' option with 'bind' to list all available Readline function names.

```bash
bind -l
```

--------------------------------

### Complex File Path Generation with Brace Expansion

Source: https://www.gnu.org/software/bash/manual/html_node/Brace-Expansion.html

Illustrates a more complex use of brace expansion for generating file paths, including nested expansions and wildcard-like patterns. This is useful for managing related files or configurations.

```bash
chown root /usr/{ucb/{ex,edit},lib/{ex?.?*,how_ex}}
```

--------------------------------

### Bind: List Current Bindings

Source: https://www.gnu.org/software/bash/manual/html_node/Bash-Builtins.html

Use the '-P' option to list current Readline function names and their associated bindings.

```bash
bind -P
```

--------------------------------

### Process Substitution for Writing Input

Source: https://www.gnu.org/software/bash/manual/html_node/Process-Substitution.html

Use the `>(list)` form to provide input to a process as if it were a file. Ensure no space between '>' and '('.

```bash
>(list)
```

--------------------------------

### Bash source command usage

Source: https://www.gnu.org/software/bash/manual/html_node/Bash-Builtins.html

Demonstrates the syntax for the 'source' command, used to execute commands from a file in the current shell. It is a synonym for '.'.

```bash
source [-p path] filename [arguments]

```

--------------------------------

### Process Substitution for Reading Output

Source: https://www.gnu.org/software/bash/manual/html_node/Process-Substitution.html

Use the `<(list)` form to read the output of a process as if it were a file. Ensure no space between '<' and '('.

```bash
<(list)
```

--------------------------------

### Set Compiler and Flags via Environment

Source: https://www.gnu.org/software/bash/manual/html_node/Compilers-and-Options.html

Use this method to specify the C compiler (CC) and compiler flags (CFLAGS) when running the `configure` script. This is useful for systems requiring specific options not automatically detected.

```bash
CC=c89 CFLAGS=-O2 LIBS=-lposix ./configure

```

--------------------------------

### Using fc for command re-execution with substitution

Source: https://www.gnu.org/software/bash/manual/html_node/Bash-History-Builtins.html

Demonstrates how to use the 'fc -s' command to re-execute a previous command after replacing a pattern with a replacement string.

```bash
r='fc -s'
```