Holberton Shell (hsh) is a simple command line shell for OS X and Linux. Hsh includes most basic features present in the bash shell. This shell was built as a project for Holberton School.
HSH works like any other shell, like bash or zsh. Detailed user documentation on specific commands is available by running help within hsh.
HSH builds successfully with a GCC 4.8.5 compiler or later. HSH can compile using gcc 4.8.4 -Wall -Werror -Wextra -pedantic *.c -o simple_shell.
To start up HSH, simply type in
./simple_shell
the terminal.
Like other shells, hsh is used by given it commands. Every hsh command follows the same general syntax: command name {arguments}. The command is executed by writing the name of the command followed by any arguements.
echo Hello Holberton
Above will run the echo command, which will write its arguements Hello Holberton to the standard output.
For more information on echo, you can use the man command. The man command displays a manual page of a given command, system call, libraries, and important files.
man echo
The hsh shell also provides various builtins, commands built into the hsh shell itself. For more information on specific builtins, you can use the help command, which provides a similar manual for the specific builtin.
help setenv
Supported syntax and lists of builtins and commands are given in their respected sections.
Any program in your computer can be used as a command in hsh. If the program is located in any of the directories in the [PATH - link include], then typing the filename is enough to run the command. Otherwise, a full path to the program is required
/Desktop/Holberton/my_echo Hello Holberton
Commands and any arguments are seperated by a ' ' . Commands end with either a newline (i.e Return Key) or a ;, &&, or ||.
To enter more than one command in one line, a ; can be used to seperate commands. Commands are read and executed left to right.
echo Hello Holberton ; ls
If commands are seperated by && , the leftmost command is read and executed and if the execution failed, no other commands are executed, otherwise, the next command in line will be executed. If the commands is seperated by || , regardless of execution failure or success of the leftmost command, all suceeded commands are executed.
Switches and flags arguements of commands are also supported by hsh. Most switches start with a hypen, - and always somehows affect the command in one way. For example, when a user inputs:
ls -a
The ls commands lists all directories and files in the current working directory. However, including the switch -a , will also include all files and directories, including hidden ones.
hsh provides support for comments added into standard input. Comments can be inputed by placing a # before any statement. Comments are ignored by hsh.
echo # Hello Holberton
The above command will not write Hello Holberton to standard output.
cat - concatenate and print files to standout output
cp - copy files to another file
grep - searches a file for a specified pattern
less - allows backward moveement in the file as well as foward movement
ls - lists all files and directories of current working directory
mv - moves one file into another file
pwd - prints out the current working directory
There are several builtins programmed into the hsh. Below is a description and use for each builtin.
To print out a list of all the environemental variables, the builtin env can be used. Each environmental variable and its value is printed out with a syntax of key=value. Each variable is seperated by a new line.
To set an environemental variable, the builtin is setenv. The syntax to use setenv is setenv key value. If one of the arguments is missing, an error is returned.
setenv holberton betty
To remove an environemental variable, the builtin unsetenv can be used. The syntax to use unsetenv is unsetenv key. If no key value is given, an error is returned.
unsetenv holberton
The cd command changes the shell working directory. The syntax to use the command is cd DIR. If no DIR is given, it is defaulted to the HOME shell variable. The full path of the directory is needed. To change the directory to its parent, the argument .. can be used.
To print out a list of previous commands used, the command history can be used. The previous 50 commands will be printed out. The history of all commands is written into the .simple_shell_history file.
To receive a description and the syntax use of a specific command, you can use the help command. To use the help builtin, the synatax is as follows
help cd
The output would include usage followed by a definition.
cd usage: cd DIR
Change the current directory to DIR
To exit out of the shell, the user may use the exit builtin. To use exit, a status number, n can be given. If n is ommited, the exit status is that of the last command executed.
exit 1
To exit out of a process or command, ctrl c is used. Control-C interrupts a process and causes it to abort.
To exit out of the hsh shell, the user can do one of the following, ctrl D or exit n. When exiting with ctrl D, an exit status of 0 is given. Using exit, you can input its exit status or it is defaulted to the status of the last command executed.