This is a simple UNIX command interpreter based on bash and Sh.
Sodashy is a sh-compatible command language interpreter that executes commands read from the standard input or from a file.
Usage: Sodash Sodash is started with the standard input connected to the terminal. To start, compile all .c located in this repository by using this command:
gcc -Wall -Werror -Wextra -pedantic *.c -o sodash
./sodash
Sodash is allowed to be invoked interactively and non-interactively. If sodash is invoked with standard input not connected to a terminal, it reads and executes received commands in order.
Example:
$ echo "echo 'holberton'" | ./sodash
'holberton'
$
When sodash is invoked with standard input connected to a terminal (determined by isatty(3), the interactive mode is opened. sodash Will be using the following prompt ^-^ .
Example:
$./sodash
^-^
If a command line argument is invoked, sodash will take that first argument as a file from which to read commands.
Example:
$ cat text
echo 'holberton'
$ ./sodash text
'holberton'
$
Upon invocation, sodash 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.
$ echo "echo $HOME" | ./sodash
/home/vagrant
The current working directory as set by the cd command.
$ echo "echo $PWD" | ./sodash
/home/vagrant/holberton/simple_shell
The previous working directory as set by the cd command.
$ echo "echo $OLDPWD" | ./sodash
/home/vagrant/holberton/bog-062019-test_suite
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.
$ echo "echo $PATH" | ./sodash
/home/vagrant/.cargo/bin:/home/vagrant/.local/bin:/home/vagrant/.rbenv/plugins/ruby-build/bin:/home/vagrant/.rbenv/shims:/home/vagrant/.rbenv/bin:/home/vagrant/.nvm/versions/node/v10.15.3/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin:/home/vagrant/.cargo/bin:/home/vagrant/workflow:/home/vagrant/.local/bin
After receiving a command, sodash 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. sodash 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, sodash 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.
sodash 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).
While running in interactive mode, sodash ignores the keyboard input ctrl+c. Alternatively, an input of End-Of-File ctrl+d will exit the program.
User hits ctrl+d in the foutrh command.
$ ./sodash
^-^ ^C
^-^ ^C
^-^ ^C
^-^
sodash interprets the $ character for variable replacement.
ENV_VARIABLE is substituted with its value.
Example:
$ echo "echo $PWD" | ./sodash
/home/vagrant/holberton/simple_shell
? is substitued with the return value of the last program executed.
Example:
$ echo "echo $?" | ./sodash
0
The second $ is substitued with the current process ID.
Example:
$ echo "echo $$" | ./sodash
3855
sodash ignores all words and characters preceeded by a # character on a line.
Example:
$ echo "echo 'holberton' #this will be ignored!" | ./sodash
'holberton'
sodash specially interprets the following operator characters:
Commands separated by a ; are executed sequentially.
Example:
$ echo "echo 'hello' ; echo 'world'" | ./sodash
'hello'
'world'
command1 && command2: command2 is executed if, and only if, command1 returns an exit status of zero.
Example:
$ echo "error! && echo 'holberton'" | ./sodash
./shellby: 1: error!: not found
$ echo "echo 'my name is' && echo 'holberton'" | ./sodash
'my name is'
'holberton'
command1 || command2: command2 is executed if, and only if, command1 returns a non-zero exit status.
Example:
$ echo "error! || echo 'wait for it'" | ./sodash
./sodash: 1: error!: not found
'wait for it'
The operators && and || have equal precedence, followed by ;.
- 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 ascd $OLDPWDand the pathname of the new working directory is printed to standad output. - If the argument,
--is given, the command is interpreted ascd $OLDPWDbut the pathname of the new working directory is not printed. - The environment variables
PWDandOLDPWDare updated after a change of directory.
Example:
$ ./sodash
^-^ pwd
/home/vagrant/holberton/simple_shell
$ cd ../
^-^ pwd
/home/vagrant/holberton
^-^ cd -
^-^ pwd
/home/vagrant/holberton/simple_shell
- Usage:
exit [STATUS] - Exits the shell.
- The
STATUSargument is the integer used to exit the shell. - If no argument is given, the command is interpreted as
exit 0.
Example:
$ ./sodash
$ exit
- Usage:
env - Prints the current environment.
Example:
$ ./sodash
$ env
NVM_DIR=/home/vagrant/.nvm
...
- Usage:
setenv [VARIABLE] [VALUE] - Initializes a new environment variable, or modifies an existing one.
- Upon failure, prints a message to
stderr.
Example:
$ ./sodash
$ setenv NAME Holberton
$ echo $NAME
Holberton
- Usage:
unsetenv [VARIABLE] - Removes an environmental variable.
- Upon failure, prints a message to
stderr.
Example:
$ ./sodash
$ setenv NAME Holberton
$ unsetenv NAME
$ echo $NAME
$
- Luis chaparro <luischaparroc>
- Edward Ortiz <edward0rtiz>
Sodash is a simple shell unix command interpreter that is part of the holberton low level programming module at Holberton School and is intended to emulate the basics sh shell. All the information given in this README is based on the sodash and bash man (1) pages.