This is a Unix command line interpreter (CLI). It implements the following built-ins: echo, cd, setenv, unsetenv, env and exit. Other commands are delegated to the system.
Note that this CLI only supports basic command lines; it does not support pipes, redirections or auto-completion, or other advanced features.
To compile the application, run make from the project's root directory.
After the project has compiled, run the my_zsh executable file.
echo -- write arguments to the standard output
echo [string ...]
The echo built-in writes any specified operands, separated by single blank (' ') characters and followed by a newline ('\n') character, to the standard output.
cd -- change the working directory
cd [-L|-P] [directory]
cd <-|~>
The cd built-in changes the working directory of the current shell execution environment.
The following options are supported by the implementation:
-L Handle the operand dot-dot logically; symbolic link
components are not resolved before dot-dot
components are processed.
-P Handle the operand dot-dot physically; symbolic link
components are resolved before dot-dot components
are processed.
If both -L and -P options are specified, the last of these options is used and all others ignored. If neither -L nor -P is specified, the operand shall be handled dot-dot logically.
The following operands are supported:
directory An absolute or relative pathname of the directory that
shall become the new working directory. The
interpretation of a relative pathname by cd depends on
the -L option and the CDPATH and PWD environment
variables. If directory is an empty string, the directory
specified by the HOME environment variable becomes the new
working directory, if that variable is set.
- When a <hyphen-minus> is used as the operand, this
shall be equivalent to the command:
cd "$OLDPWD" && pwd
which changes to the previous working directory and
then writes its name.
~ When a <tilde> is used as the operand, this
shall be equivalent to the command:
cd "$HOME"
which changes to the directory specified by the HOME environment
variable, if that variable is set.
setenv -- change or add an environment variable
setenv [-o] [name=value ...]
The setenv built-in adds the variable name to the environment with the value value, if name does not already exist. If name does exist in the environment, then its value is changed to value if the option -o is specified; if -o is not specified, then the value of name is not changed.
The -o option is only recognized when it is specified before any name=value argument.
unsetenv -- remove an environment variable
unsetenv [name ...]
The unsetenv built-in shall remove environment variables from the environment of the command line interpreter. The name argument is the name of a variable to be removed. The named arguments shall not contain an '=' character. If a named variable does not exist in the current environment, the environment shall be unchanged and the function is considered to have completed successfully.
env -- set environment and execute command, or print environment
env [-i] [[-u <name>] ...] [name=value ...] [utility [argument ...]]
The env built-in executes another utility after modifying the environment as specified on the command line. Each name=value option specifies the setting of an environment variable, name, with a value of value. All such environment variables are set before the utility is executed.
If no utility is specified, env prints out the names and values of the variables in the environment, with one name/value pair per line.
-i Execute the utility with only those environment variables
specified by name=value options. The environment inherited
by env is ignored completely.
-u name
If the environment variable name is in the environment,
then remove it before processing the remaining options.
The value for name must not include the `=' character.
The above options are only recognized when they are specified before any name=value options.
exit -- cause the command line interpreter to exit
exit [n]
The exit utility shall cause the command-line interpreter to exit from its current execution environment with the exit status specified by the unsigned 8-bit integer n. If n is specified, but cannot be converted to an unsigned integer value, the exit status is 0. If n is specified, but its value is not between 0 and 255 inclusively, the exit status is n % 256. Note that for any integer n, n % 256 == n - 256 * floor(n / 256), where floor(x) rounds x towards minus infinity.
As a central architecture principle, a Command interface is defined, which consists of only one method named execute. All commands implement the Command interface, and throughout the program, the code only deals with the Command abstract type. There are no CdCommand or EchoCommand types, nor any other type representing a concrete command.
There is, however, an abstract type representing a concrete command class: ConcreteCommandClass, which consists of a single method named fromArguments. All concrete command types implement the ConcreteCommandClass interface, in order to provide a uniform way to construct a concrete command from a list of arguments.
When the application has to build a concrete command, the choice of the right concrete command class is centralized in one place, i.e. the ConcreteCommandClassFactory.
The code base also generally uses a coding style called "C-plus", emulating object-oriented programming and encapsulation of data with the C programming language.