cli.py

import argparse
import sys

import proc_reader as pr


def format_kb(kb):
    """Pretty-print a kB value as MB/GB depending on magnitude."""
    if kb >= 1024 * 1024:
        return f"{kb / (1024 * 1024):.2f} GB"
    if kb >= 1024:
        return f"{kb / 1024:.1f} MB"
    return f"{kb} kB"


def format_uptime(seconds):
    seconds = int(seconds)
    h, rem = divmod(seconds, 3600)
    m, s = divmod(rem, 60)
    return f"{h}h {m}m {s}s"


def cmd_mem(_args):
    mem = pr.get_meminfo()
    print("System memory (from /proc/meminfo)")
    print("-" * 40)
    print(f"  Total:     {format_kb(mem['total_kb'])}")
    print(f"  Used:      {format_kb(mem['used_kb'])} ({mem['used_percent']}%)")
    print(f"  Free:      {format_kb(mem['free_kb'])}")
    print(f"  Cached:    {format_kb(mem['cached_kb'])}")
    print(f"  Available: {format_kb(mem['available_kb'])}")


def cmd_list(_args):
    print(f"{'PID':>7}  {'STATE':<24}  {'RSS':>10}  NAME")
    print("-" * 60)
    for pid in pr.list_pids():
        try:
            info = pr.get_status(pid)
        except (pr.ProcessNotFound, PermissionError):
            # Process exited between listing and reading, or needs root.
            continue
        print(
            f"{info['pid']:>7}  {info['state']:<24}  "
            f"{format_kb(info['vm_rss_kb']):>10}  {info['name']}"
        )


def cmd_process(args):
    try:
        info = pr.get_process_info(args.pid)
    except pr.ProcessNotFound:
        print(f"No such process: {args.pid}", file=sys.stderr)
        sys.exit(1)
    except PermissionError:
        print(f"Permission denied reading PID {args.pid} (try sudo)", file=sys.stderr)
        sys.exit(1)

    print(f"Process {info['pid']} ({info['name']})")
    print("-" * 40)
    print(f"  Command:  {info['cmdline']}")
    print(f"  State:    {info['state']}")
    print(f"  Parent:   {info['ppid']}")
    print(f"  Threads:  {info['threads']}")
    print(f"  Uptime:   {format_uptime(info['uptime_seconds'])}")
    print(f"  VmSize:   {format_kb(info['vm_size_kb'])} (virtual)")
    print(f"  VmRSS:    {format_kb(info['vm_rss_kb'])} (resident)")


def main():
    parser = argparse.ArgumentParser(
        description="Inspect Linux process and memory stats via /proc directly."
    )
    sub = parser.add_subparsers(dest="command", required=True)

    sub.add_parser("mem", help="Show system-wide memory summary").set_defaults(func=cmd_mem)
    sub.add_parser("list", help="List all running processes").set_defaults(func=cmd_list)

    p_process = sub.add_parser("process", help="Show details for one PID")
    p_process.add_argument("pid", type=int)
    p_process.set_defaults(func=cmd_process)

    args = parser.parse_args()
    args.func(args)


if __name__ == "__main__":
    main()