Bashanelli (bnli)

This project was a joint project - Credits to @Leo @RoryBrownie @SkeneLord

An exercise in finding out that bash was way more extensive than we first thought.

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Features

• External program support
• Shell script support
• A bunch of builtins
• Redirection
• Profile loading
• Custom PS1
• History
• Cycling through previous commands (up/down arrows)

_{also we implemented our own readline! 👍}

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Profiles

Profiles are shell scripts that are ran on launch of Bashanelli.

Bash Profile

Bashanelli will attempt to load standard bash and sh profiles (~/.profile, ~/.bash_profile, etc) upon launch. _{Currently disabled as Bashanelli cannot handle conditions and loops, which bash profiles are full of.}

Bashanelli Profile

Bashanelli loads its own profile on launch.

This is loaded from ~/.bnli_profile, if such a file exists.

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Custom PS1

Bashanelli parses its PS1 (prompt) string from the $PS1 environment variable.

In order to set a custom PS1 you can add the following line to ~/.bnli_profile:

export PS1=<custom PS1>

Control Chars

Note that control characters must be double escaped as the slashes are escaped while parsing the export statement, as well as when parsing the PS1.

• \\h - Hostname, up to the first appearance of .
• \\H - Hostname
• \\u - Login
• \\s - The name of the shell (Usually "bashanelli")
• \\w - The current working directory
• \\n - Newline char (\n)

ANSI Escape Sequences

ANSI escape codes can be used (for colour and formatting).

They must be written in the following form:

"\\033[<ANSI code>m"

Example

export PS1="\\033[1m\\033[32m\\u@\\h\\033[0m:\\033[1m\\033[34m\\w\\033[0m\\033[1m> \\033[0m"

With a user "bob" on a machine "myComputer", the PS1 will look as follows:

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History

Bashanelli uses a bash-style history that keeps track of previously entered commands.

The history is stored in ~/.bnli_history.

Invocations

• !! - Execute last command.
• !<n> - Executes the n^th command from the history.
• !<-n> - Executes the n^th last command from the history.

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Builtins

cd

Changes the working directory. Providing no args changes the working directory to $HOME.

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history

Prints each line in the history along with its assosciated number.

Flags

• -c / --clear - Clears the history.

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export

Sets an environment variable to a given value.

Flags

• -p - Prints all environment variables.

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unset

Unsets the value of a given environment variable.

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alias

Assigns an alias to a given command.

Flags

• -p - Prints all aliases.

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unalias

Removes a given alias.

Flags

• -a - Removes all aliases.

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builtin

Executes a given command as a builtin.

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source

Executes a given command as a shell script.

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exec

Executes a given command as an executable program.

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exit

Quits the shell with exit code 0.