This is a collaborative project by Authors : OLANOTAN92 and OMAJUGHOLEE
Requirements
General Allowed editors: vi, vim, emacs All your files will be compiled on Ubuntu 20.04 LTS using gcc, using the options -Wall -Werror -Wextra -pedantic -std=gnu89 All your files should end with a new line A README.md file, at the root of the folder of the project is mandatory Your code should use the Betty style. It will be checked using betty-style.pl and betty-doc.pl Your shell should not have any memory leaks No more than 5 functions per file All your header files should be include guarded Use system calls only when you need to (why?) Write a README with the description of your project You should have an AUTHORS file at the root of your repository, listing all individuals having contributed content to the repository. Format, see Docker.
Output Unless specified otherwise, your program must have the exact same output as sh (/bin/sh) as well as the exact same error output. The only difference is when you print an error, the name of the program must be equivalent to your argv[0] (See below) Example of error with sh:
$ echo "qwerty" | /bin/sh /bin/sh: 1: qwerty: not found $ echo "qwerty" | /bin/../bin/sh /bin/../bin/sh: 1: qwerty: not found $ Same error with your program hsh:
$ echo "qwerty" | ./hsh ./hsh: 1: qwerty: not found $ echo "qwerty" | ./././hsh ./././hsh: 1: qwerty: not found $
List of allowed functions and system calls access (man 2 access) chdir (man 2 chdir) close (man 2 close) closedir (man 3 closedir) execve (man 2 execve) exit (man 3 exit) _exit (man 2 _exit) fflush (man 3 fflush) fork (man 2 fork) free (man 3 free) getcwd (man 3 getcwd) getline (man 3 getline) getpid (man 2 getpid) isatty (man 3 isatty) kill (man 2 kill) malloc (man 3 malloc) open (man 2 open) opendir (man 3 opendir) perror (man 3 perror) read (man 2 read) readdir (man 3 readdir) signal (man 2 signal) stat (__xstat) (man 2 stat) lstat (__lxstat) (man 2 lstat) fstat (__fxstat) (man 2 fstat) strtok (man 3 strtok) wait (man 2 wait) waitpid (man 2 waitpid) wait3 (man 2 wait3) wait4 (man 2 wait4) write (man 2 write) Compilation Your shell will be compiled this way:
gcc -Wall -Werror -Wextra -pedantic -std=gnu89 *.c -o hsh
Testing Your shell should work like this in interactive mode:
$ ./hsh
(
But also in non-interactive mode:
$ echo "/bin/ls" | ./hsh hsh main.c shell.c test_ls_2 $ $ cat test_ls_2 /bin/ls /bin/ls $ $ cat test_ls_2 | ./hsh hsh main.c shell.c test_ls_2 hsh main.c shell.c test_ls_2 $
Checks The Checker will be released at the end of the project (1-2 days before the deadline). We strongly encourage the entire class to work together to create a suite of checks covering both regular tests and edge cases for each task. See task 8. Test suite.
Environment 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:
HOME The home directory of the current user and the default directory argument for the cd builtin command.
$ echo "echo $HOME" | ./hsh /home/projects PWD The current working directory as set by the cd command.
$ echo "echo $PWD" | ./hsh /home/projects/alx/simple_shell OLDPWD The previous working directory as set by the cd command.
$ echo "echo $OLDPWD" | ./hsh /home/projects/alx/printf 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.
$ echo "echo $PATH" | ./hsh /home/projects/.cargo/bin:/home/projects/.local/bin:/home/projects/.rbenv/plugins/ruby-build/bin:/home/projects/.rbenv/shims:/home/projects/.rbenv/bin:/home/projects/.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/projects/.cargo/bin:/home/projects/workflow:/home/projects/.local/bin Command Execution 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. Exit Status 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).
Signals While running in interactive mode, hsh 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 third line.
$ ./hsh $ ^C $ ^C $ Variable Replacement hsh interprets the $ character for variable replacement.
$ENV_VARIABLE ENV_VARIABLE is substituted with its value.
Example:
$ echo "echo
Example:
$ echo "echo
Example:
$ echo "echo $$" | ./hsh 6494 Comments hsh ignores all words and characters preceeded by a # character on a line.
Example:
$ echo "echo 'hello' #this will be ignored!" | ./hsh 'hello' Operators hsh specially interprets the following operator characters:
; - Command separator Commands separated by a ; are executed sequentially.
Example:
$ echo "echo 'hello' ; echo 'world'" | ./hsh 'hello' 'world' && - AND logical operator command1 && command2: command2 is executed if, and only if, command1 returns an exit status of zero.
Example:
$ echo "error! && echo 'hello'" | ./hsh ./hsh: 1: error!: not found $ echo "echo 'all good' && echo 'hello'" | ./hsh 'all good' 'hello' || - OR logical operator command1 || command2: command2 is executed if, and only if, command1 returns a non-zero exit status.
Example:
$ echo "error! || echo 'but still runs'" | ./hsh ./hsh: 1: error!: not found 'but still runs' The operators && and || have equal precedence, followed by ;.
hsh 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. Example:
$ ./hsh $ pwd /home/projects/alx/simple_shell $ cd ../ $ pwd /home/projects/alx $ cd - $ pwd /home/projects/alx/simple_shell alias Usage: alias [NAME[='VALUE'] ...] Handles aliases. alias: Prints a list of all aliases, one per line, in the form NAME='VALUE'. alias NAME [NAME2 ...]: Prints the aliases NAME, NAME2, etc. one per line, in the form NAME='VALUE'. alias NAME='VALUE' [...]: Defines an alias for each NAME whose VALUE is given. If name is already an alias, its value is replaced with VALUE. Example:
$ ./hsh $ alias show=ls $ show AUTHORS builtins_help_2.c errors.c linkedlist.c shell.h test README.md env_builtins.c getline.c locate.c hsh alias_builtins.c environ.c helper.c main.c split.c builtin.c err_msgs1.c helpers_2.c man_1_simple_shell str_funcs1.c builtins_help_1.c err_msgs2.c input_helpers.c proc_file_comm.c str_funcs2.c 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. Example:
$ ./hsh $ exit env Usage: env Prints the current environment. Example:
$ ./hsh $ env NVM_DIR=/home/projects/.nvm ... setenv Usage: setenv [VARIABLE] [VALUE] Initializes a new environment variable, or modifies an existing one. Upon failure, prints a message to stderr. Example:
$ ./hsh $ setenv NAME Poppy $ echo $NAME Poppy unsetenv Usage: unsetenv [VARIABLE] Removes an environmental variable. Upon failure, prints a message to stderr. Example:
$ ./hsh $ setenv NAME Poppy $ unsetenv NAME $ echo $NAME
What we learned: How to collaborate as a team and work on a task Excecuting a program from another program Creating, forking and working with processes handling dynamic memory alloction in a large program