ps.p6

use v6;

my \pids = gather for dir('/proc') -> IO::Path:D $_ {
    try { take .Int }

}

role StrictKeys[@keys] { method AT-KEY (\key) { (key ∈ @keys) ?? nextsame() !! fail "key «{key}» not found"  } }

for pids -> $pid {
    my %fields is default('<unkown>') does StrictKeys[<Name Pid Uid State VmRSS>]
        = slurp("/proc/$pid/status").lines».split(":\t").flat».trim;
    CATCH { when X::IO { next } }
    
    %fields<Uid> = %fields<Uid>.split("\t")[0];
    
    constant format =     <%6s    %-15s           %-10s      %-10s      %-10s>.join("\t") ~ "\n";
    FIRST printf format,  <PID    NAME            USER       STATE      MEMORY>;
    FIRST printf format,  <------ --------------- ---------- ---------- ---------->;
    printf format, %fields<Pid    Name            Uid        State      VmRSS>;
}