SBUnix

=====70 POINT PROJECT=====

==USEFUL TIPS==

For filesystem, use the disk named "hdd.img" in cse506 folder. Disk Image size is 20 MB

If new disk is to created, here are the following steps:

1. Run the qemu command to create a 1 MB disk named "hdd.img" : qemu-img create hdd.img 20M 

2. Insert superblock to that image using command : dd if=superblock of=hdd.img seek=1 conv=notrunc (superblock file is provided in the home directory, which is being generated using initialize_superblock.c)

3. Now, the hdd.img is ready to be used by our OS. Run Qemu with following command : qemu-system-x86_64 -curses -cdrom $USER.iso -drive id=disk,file=hdd.img,if=none -device ahci,id=ahci -device ide-drive,drive=disk,bus=ahci.0 -gdb tcp::$1

For Shutdown : type shutdown on shell.

For any queries, please contact SBUnix developers.

==SYSTEM CALLS== /* File System Commands */
READ() Syntax : read(file *file, uint64_t addr, char *buf ) Description : Whenever called this function reads the file in to the buffer 'buf'. Dependencies : To open a file always use OPEN system call before reading and after the read is completed, close the file. This call returns -1 for the files whose WRONLY flag is set. return : This call returns the length of bytes read into the buffer or -1 if there is an error

WRITE() 
Syntax       :  int write(file *fd, char * buf, int size)
Description  :  Whenever called it writes up to 'size' number of bytes into the file descriptor 'fd' from the buffer starting at 'addr'.
Dependencies :  To open a file always use OPEN system call before reading and after the read is completed, close the file.
                This call returns -1 for the files opened with O_RDONLY flag set. It cannot do any write operations on tarfs.
return       :  This function retruns length of bytes written into the buffer or -1 on error

MALLOC()
Syntax       :  void *malloc(uint64_t size)
Description  :  Whenever called the size of vma is increased by 'size'.
return       :  This call returns the virtual address in heap

FORK()
Syntax       :  pid_t fork (void); 
Description  :  Whenever called a child process is created. It returns pid = 0 for child process and non zero for parent process.
return       :  This call returns the pid for parent process or 0 for the child  process.

EXECVPE()
Syntax       :  execvpe(char *file, char *argv[], char *envp[])
Description  :  Whenever called a file along with any necessary arguments argv[] in the environment envp[] is executed.
return       :  This call returns -1 on failure, and doesnot return anything on success

WAIT()
Syntax       :  wait(uint64_t status)
Description  :  Whenever called, the parent waits for a child process to exit.
return       :  This call returns -1 if the parent has no children.

EXIT()
Syntax       :  exit(int status)
Description  :  Whenever called the calling process is terminated immediately.

GETPID()
Syntax       :  getpid()
Description  :  Whenever called the process id of currently running process is returned.

GETPPID()
Syntax       :  getppid()
Description  :  Whenever called the parent's process id of currently running process is returned.

PS()
Syntax       :  ps()
Description  :  Whenever called the list of all currently running processes is returned.

OPENDIR()
Syntax       :  opendir(uint64_t* entry, uint64_t* directory)
Description  :  Whenever called,a directory struct with list of all inode/files in it is returned.
return       :  If an error occurs it will return directory struct with the values set to NULL.   

READDIR()
Syntax       :  readdir(DIR* node)
Description  :  Whenver called iteratively, it will list contents in directory. 
Dependencies :  Read directory system call is always followed after open directory system call.
return       :  It will return the pointer to dirent structure .If end of directory is reached or an error occurs then it returns NULL.

OPEN()
Syntax       :  open(char* dir_path, uint64_t flags)
Description  :  Whenever called, a file is opened and a file descriptor is returned. It opens files from 'tarfs' and disk depending on 'dir_path'.
Dependencies :  The flags can be one of the following: 'O_CREAT', 'O_RDONLY', 'O_WRONLY', 'O_APPEND', 'O_TRUNC', 'O_RDWR'.
return       :  This call returns file descriptor number open on a directory returns -1 as file descriptor.

SLEEP()
Syntax       :  sleep(int msec)
Description  :  The state of the current task is changed to 'sleep' for 'msec' milliseconds.

CLEAR()
Syntax       :  clear()
Description  :  Clears the screen.

SEEK()
Syntax       :  seek(uint64_t fd_type, int offset, int whence) 
Description  :  When used it will move the current file pointer by offset number of bytes that is in the file.
Dependencies :  whence can be SEEK_SET, SEEK_CUR, SEEK_END. Using this will provide the offset from start , current pointer or end of file.

SHUTDOWN()
Syntax       :  shutdown() 
Description  :  This function is used to exit from all the processes.