simple_shell

0x16. C - Simple Shell - group project at Alx - shellscripting - c_programming

simple shell:-

This project is about building a simple command line prompt that takes the most basics of commands that are present in the bash shell and runs them. the program must have the exact same output as sh (/bin/sh) as well as the exact same error output.

The shell will work after being compiled using ** gcc -Wall -Werror -Wextra -pedantic -std=gnu89 .c -o hsh*

HOME

The home directory of the current user and the default directory argument for the cd builtin command.

PWD

The current working directory as set by the cd command.

OLDPWD

The previous working directory as set by the cd command.

PATH

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 directory.

$ENV_VARIABLE

ENV_VARIABLE is substituted with its value.

$?

? is substitued with the return value of the last program executed.

$$

The second $ is substitued with the current process ID.

; - Command separator

Commands separated by a ; are executed sequentially.

&& - AND logical operator

command1 && command2: command2 is executed if, and only if, command1 returns an exit status of zero.

|| - OR logical operator

command1 || command2: command2 is executed if, and only if, command1 returns a non-zero exit status.

The operators && and || have equal precedence, followed by ;.

Builtin Commands

cd

• Usage: cd [DIRECTORY]
• Changes the current directory of the process to DIRECTORY.
• If no argument is given, the command is interpreted as cd $HOME.
• If the argument - is given, the command is interpreted as cd $OLDPWD and the pathname of the new working directory is printed to standad output.
• If the argument, -- is given, the command is interpreted as cd $OLDPWD but the pathname of the new working directory is not printed.
• The environment variables PWD and OLDPWD are updated after a change of directory.

exit

• Usage: exit [STATUS]
• Exits the shell.
• The STATUS argument is the integer used to exit the shell.
• If no argument is given, the command is interpreted as exit 0.

env

• Usage: env
• Prints the current environment.

setenv

• Usage: setenv [VARIABLE] [VALUE]
• Initializes a new environment variable, or modifies an existing one.
• Upon failure, prints a message to stderr.

unsetenv

• Usage: unsetenv [VARIABLE]
• Removes an environmental variable.
• Upon failure, prints a message to stderr.

Launching the shell

After compiling the code run this ./shell

• Output: prompt to terminal: $

Authors

• Helen Teka - https://github.com/93Helu
• Habtamu Wolde - https://github.com/Habtwolde