Add ps command to user space

[geoweb999]

ps displays information about active processes. The initial version will display all processes: pid, parent pid, current state, memory size, and program name. Processes in UNUSED state will be ignored. The initial version will support a -h flag for program information.

Approach: Update kernel as needed to introduce 22nd system call: getprocs and sys_getprocs. ps will pass a struct (ptable data) array pointer to the system call (getprocs). getprocs will iterate through all ptable entries where state != UNUSED and update the passed struct array pointer with ptable data via copyout. ps will output the returned ptable data in a nicely formatted manner. If the -h argument is used, ps will output simple help information and exit.

Files to be modified/added:

kernel:

• syscall.c (sys_getprocs function declaration, update syscalls)
• syscall.h (define SYS_getprocs 22)
• sysproc.c (function sys_getprocs)
• usys.S (add SYSCALL(getprocs))
• proc.c (code for getprocs)
• refs.h (function declaration)

user:

• user.h (add system call)
• ps.c (new: call getprocs and output returned ptable data)

Future Development

• Add support for outputting command line (argv[0]) and arguments (argv[1..n]) instead of process name.
• Add support for -t flag to output process information by parent/child in tree format

[geoweb999]

add update usys.pl

[malensek]

This is beautiful, your project is approved.

+1000000 matthew respect points