Command Prompt to Start New Bourne Again Shell

What is bash (Bourne Once again Shell)?

Fustigate (Bourne Again Beat out) is the free and enhanced version of the Bourne beat out distributed with Linux and GNU operating systems. Fustigate is similar to the original, but has added features such as command-line editing.

Created to improve on the earlier Bourne shell (named sh), Fustigate includes features from the Korn shell and the C shell. Bash is intended to adapt to the beat standard specified as function of IEEE POSIX. A command language script written for the Bourne beat should also run in the bash shell.

Bash is released under the GNU General Public License (GPL), and it is bachelor for most versions of Unix and Linux and versions take been ported to MS-DOS and Windows.

As explained in the Bash Reference Manual, the name fustigate is an acronym of "Bourne-again SHell" which is a pun on Stephen Bourne, author of the Bourne crush. Fustigate is a superset of the earlier shell, and generally uniform with Bourne shell programs.

What is a shell?

In computing, a beat out plan provides access to an operating organisation's components. The vanquish gives users (or other programs) a way to get "inside" the system; the shell defines the purlieus betwixt inside and outside.

There are 2 types of operating organisation shells:

Command-line interface (CLI) shells like fustigate offering users a curtailed and efficient mode of interacting with the Bone, without requiring the overhead of a graphic user interface.
Graphical user interface (GUI) shells, such as Windows and macOS, are considered easier for beginners to use, but usually too offer programs that emulate a CLI-based shell for arrangement administrators or other power users who adopt to collaborate at a command prompt.

Fustigate is the near commonly used CLI shell for Unix-based OSes, including Linux.

What is bash used for?

Fustigate, like other CLIs, is used for any computer application that requires precision when working with files and data, especially where large numbers of files or large quantities of data need to exist searched, sorted, manipulated or processed in any way.

Some of the almost mutual Bash utilise cases include:

System administrators use Bash to manage systems systematically and reproducibly. System administrators apply Fustigate to troubleshoot systems that are not functioning as desired or expected by logging in to systems and reviewing organisation configurations and network connections. System administrators also rely on Bash scripts to distribute software updates and patches, to monitor running systems, and to update and configure systems.
Software developers rely on Bash for many evolution tasks. Bash can be used to automate software development tasks such as code compilation, debugging source code, change management and software testing.
Network engineers employ Fustigate to test, configure and optimize network performance on organizational networks.
Computer science researchers use Fustigate to manage enquiry systems and to bear out research on those systems.
Hobbyists and power users use Bash to interact with their systems, execute programs and maintain their systems.

Fustigate is usually used interactively, but it tin can also exist used to write shell scripts. Almost any calculator chore can be automatic using a Bash script. Bash scripts tin be run on-demand or scheduled to run periodically.

How does bash work?

At offset sight bash appears to be a simple control/response system, where users enter commands and bash returns the results after those commands are run. Notwithstanding, bash is also a programming platform and users are enabled to write programs that accept input and produce output using vanquish commands in beat scripts.

One of the most basic bash commands, ls, does 1 thing: list directory contents. By itself this command lists only the names of files and subdirectories in the electric current working directory.

Output from bash ls command without parameters — Output from the fustigate ls control includes only file and directory names.

The ls command has numerous parameters that change how the results are displayed. Some frequently used parameters used with the ls control include:

ls command-line arguments (parameters)	Purpose
-50	Use a longer, more detailed, listing format to include file permissions, file owner, group, size and engagement/time of creation.
-a	Listing all files and subdirectories, even those that are ordinarily intended to be hidden.
-s	Display the size of each file.
-h	Display file and subdirectory sizes in homo-readable format using K, Chiliad, G so on to indicate kilobytes, megabytes and gigabytes.
-R	Recursive listing of all files and subdirectories under the current working directory.

Used all together, these parameters give the user a much clearer sense of what files and subdirectories are in a directory, when they have last been changed and by whom.

Bash piping pipes — Employ pipes to filter out the desired information from bash commands.

Bash enables combining commands by piping output of ane command to be used as the input for another command. For example, this command can exist used to list all files on a file system using the -R parameter to specify the listing should be recursive:

[email protected]:/$ 1s -1ashR

The response to this command, especially when issued from the system root directory, contains as well many entries for humans to parse hands. This is where pipes can come into play, in this case, the user can pipe the output from the ls control to the Bash text design matching command, grep.

The pipe symbol (vertical bar, or "|") directs output from the directory listing into the grep command to return only files and subdirectories with filenames that include the specified text pattern. This command:

[electronic mail protected]:/$ 1s -1ashR |grep 'filename.txt'

returns only files that include the string 'filename.txt' so this command tin can be used to locate a specific file.

Some things that are much easier to practice interactively from the bash command line include:

file and directory management;
checking on network configuration;
editing a configuration file (or whatever text file); and
showing the difference betwixt ii files.

Types of bash commands include:

Simple commands, which unremarkably are run by themselves or with parameters and variables. For example, the ls command takes parameters as well every bit variables relating to the directories or files to be listed.
Pipes, which are used to link the output of ane or more commands as input to other commands.
Lists, which enable users to run multiple commands in sequence.
Compound commands, which enable script programming and include loops (for repeating a command a specific number of times) and conditional constructs (for running commands only when a specific condition is met).

Command-line editing is ane special fustigate feature not e'er available with other CLIs. Bash retains a command history, which tin can exist accessed by pressing the upwardly arrow cardinal. This makes it easier to precisely rerun a command. These prior commands tin likewise exist modified at the control line, using special keys to re-create, paste, delete or modify a prior command.

Fustigate is one of the foundations of modern system and network assistants, and new users face a learning curve when using it. However, once learned, bash skills are forever: a time-traveling system administrator from 1992 would likely be able to get right dorsum to work on a modernistic Linux arrangement, using bash. Learn more nigh how Bash scripting from this tutorial on creating a fustigate shell that accepts arguments when information technology runs.

This was last updated in December 2021