A simple shell project that works similar to sh.
To compile, gcc -Wall -Wextra -Werror -pedantic -std=gnu89 *.c -o hsh
To start shell, type ./hsh and enter.
Project was completed using
- C language
- Shell
- Betty linter
hsh is a simple UNIX command language interpreter that reads commands from either a file or standard input and executes them.
- Prints a prompt and waits for a command from the user
- Creates a child process in which the command is checked
- Checks for built-ins, aliases in the PATH, and local executable programs
- The child process is replaced by the command, which accepts arguments
- When the command is done, the program returns to the parent process and prints the prompt
- The program is ready to receive a new command
- To exit: press Ctrl-D or enter "exit" (with or without a status)
- Works also in non interactive mode
Usage: hsh [filename]
To invoke hsh, compile all .c files in the repository and run the resulting executable.
hsh can be invoked both interactively and non-interactively. If hsh is invoked with standard input not connected to a terminal, it reads and executes received commands in order.
Upon invocation, hsh receives and copies the environment of the parent process in which it was executed. This environment is an array of name-value strings describing variables in the format NAME=VALUE. A few key environmental variables are:
The home directory of the current user and the default directory argument for the cd builtin command.
A colon-separated list of directories in which the shell looks for commands. A null directory name in the path (represented by any of two adjacent colons, an initial colon, or a trailing colon) indicates the current directoryi.
After receiving a command, hsh tokenizes it into words using " " as a delimiter. The first word is considered the command and all remaining words are considered arguments to that command. hsh then proceeds with the following actions:
If the first character of the command is neither a slash () nor dot (.), the shell searches for it in the list of shell builtins. If there exists a builtin by that name, the builtin is invoked. If the first character of the command is none of a slash (), dot (.), nor builtin, hsh searches each element of the PATH environmental variable for a directory containing an executable file by that name. If the first character of the command is a slash () or dot (.) or either of the above searches was successful, the shell executes the named program with any remaining given arguments in a separate execution environment.
hsh returns the exit status of the last command executed, with zero indicating success and non-zero indicating failure.
If a command is not found, the return status is 127; if a command is found but is not executable, the return status is 126.
All builtins return zero on success and one or two on incorrect usage (indicated by a corresponding error message).