,A PROCESS IS A RUNN+ PROGRAM  A PID1 AN
ADDRESS SPACE1 OP5 FILE DESCRIPTORS1 A
P>5T1 A /ATE4 ,E PROCESS ON ,L9UX
DESC5DS F ,,PID #A "<9IT_/SY/EMD"> "?
=K"<">  ! :OLE SY/EM IS "O FAMILY TREE4
,? *APT] T1*ES Y TO SEE X3 PS1 TOP1
SIGNALS1 JOB 3TROL1 & ! _/PROC FILESY/EM
": ! K]NEL EXPOSES E PROCESS'S 9N>DS Z
R1DABLE FILES4
,! LIFECYCLE  =K1 EXEC1 WAIT1 EXIT
PID "7 =K"<">2        _/_/ CL"O  P>5T &
* BO? 3T9UE IF "<PID "7"7 #J">       
_/_/ * BRAN*     EXECVP"<8PROG01 >GS">2 
_/_/ REPLACE ? PROCESS'S IMAGE ELSE    
WAIT"<@&/ATUS">2   _/_/ P>5T COLLECTS !
*'S EXIT CODE
=K"<"> DUPLICATES2 EXEC"<"> REPLACES !
COPY ) ! NEW PROGRAM2 WAIT"<"> R1PS4 ,E
PROCESS IS BORN A CL"O ( XS P>5T1 !N
RE-SK9N$ Z XS R1L PROGRAM4 ,! EXIT CODE
"<#J#BEE"> ! * L1VES IS ! 3TRACT ! P>5T
COLLECTS  @S8 9 ! %ELL4
,:5 A * DIES 2F XS P>5T WAITS1 X 2COMES
A ZOMBIE  ;,Z 9 PS1 D1D B UNR1P$1 HOLD+
ONLY XS EXIT /ATUS4 ,AN ORPHAN ^: P>5T
DIES IS RE-P>5T$ TO ,,PID #A4
,SEE+ !M  PS & FRS
PS AUX                  _? ! CLASSIC
FULL LI/+ _? ,,US]  ,,PID .0,,CPU
.0,,,MEM VSZ RSS TTY /AT />T "T COMM&,'
PS -EF                  _? ,SYS,V /YLE 
%[S ,,PPID PS -EJ,H                 _? !
FAMILY TREE PS --=E/ -;E          _?
VISUAL TREE PGREP -;L S%D           _?
PIDS BY "N PID( BA%              _? S+LE
"N  PIDS TOP                     _? !
LIVE VIEW  SORT BY ;,M"<EM">1
;,P"<CPU">1 ;,T"<IME"> HTOP             
_? ! BETT] LIVE VIEW P/REE -;P          
_? ! TREE ) PIDS
,,/AT CODES  ;,R RUNN+1 ;,S SLEEP+1 ;,D
UN9T]RUPTIBLE "<USUALLY ,I_/,O">1 ;,T
/OPP$1 ;,Z ZOMBIE1 ;S SES.N L1D]1 "6
=EGR.D1 ;L MULTI?R1D$4 ;,D-/ATE
PROCESSES C'T 2 KILL$  !Y'RE MID-SYSCALL
9 ! K]NEL4
,JOB 3TROL  ! %ELL'S [N PROCESSES
CMD @&               _? BACKGR.D JOBS   
_? ! JOB TABLE  .0#A .0#B 444 FG .0#A   
_? BR+ TO =EGR.D BG .0#A              
_? RESUME SUSP5D$ 9 BACKGR.D ,CTRL-;,Z2
BG          _? ! SUSP5D-&-BACKGR.D COMBO
4[N .0#A           _? REMOVE F JOB TABLE
SURVIVES %ELL EXIT NOHUP CMD @&        
_? IMMUNE TO ,,SI<UP  SURVIVES LOG\T
,CTRL-;,C "7 ,,SIG9T TO ! =EGR.D GR\P2
,CTRL-;,Z "7 ,,SIGT/P2 ,CTRL-_* "7
,,SIGQUIT "<) CORE DUMP">4 JOBS -;L %[S
PIDS4
,SES.NS & PROCESS GR\PS
,A SES.N GR\PS PROCESS GR\PS "U A
3TROLL+ T]M9AL  SETSID />TS A NEW "O
"<H[ DAEMONS DETA* F T]M9ALS">4 ,! LOG9
%ELL L1DS A SES.N2 PKILL -;U ALICE KILLS
ALL H] PROCESSES4 ,DAEMONIZA;N "7 =K1
SETSID1 DETA* TTY1 *DIR _/1 CLOSE FDS1
R$IRECT /DIO TO _/DEV_/NULL  ! CLASSIC
D.E SY/EMD N[ DOES = S]VICES4
,! =K_/EXEC_/EXEC FAMILY  ! ;,C-LEVEL
ANATOMY
PID.-T PID "7 =K"<">2          _/_/ CL"O
P>5T"6* BO? 3T9UE1 DI6] 9 RETURN IF
"<PID "7"7 #J"> _<              _/_/ *  
EXECLP"<8PROG01 8PROG01 8>G01 ,,NULL">2 
_/_/ ,,PA?-SE>*$ EXEC    
.-EXIT"<#ABG">2                         
_/_/ ONLY R1*$ IF EXEC FAILS _> _/_/
P>5T 3T9UES ) PID "7 *'S PID 9T /ATUS2
WAITPID"<PID1 @&/ATUS1 #J">2    _/_/
COLLECT ! EXIT CODE ,,WIFEXIT$"</ATUS">2
,,WEXIT/ATUS"</ATUS">2    _/_/ DECODE X
,! EXEC FAMILY3
EXECL_/EXECLP_/EXECLE_/EXECV_/EXECVP_/EXECVPE
L"7>G-LI/1 V"7>GV->RAY1 P"7,,PA?-SE>*1
E"7CU/OM 5V4 ,AF EXEC ! PROCESS'S :OLE
IMAGE IS REPLAC$  SAME PID1 NEW PROGRAM4
,! ZOMBIE_/ORPHAN LOGIC3 A * EXITS 
,,SIG*LD TO P>5T  P>5T WAIT"<">;S  R1P$2
P>5T DIES F/  * REP>5TS TO ,,PID #A4
,! PROCESS TREE'S /RUCTURE
P/REE -;P            _? ! VISUAL FAMILY 
F SY/EMD_/,,PID#A D[N PS -EJ,H          
_? ! SAME TREE Z A LI/ PS -O
PID1PPID1PGID1SID1TTY1CMD -;E _? ,,PID
#A3 SY/EMD "<OR 9IT"> _?    S%D  BA% 
VIM _?    CRON _?    GETTY "<#F"> _?   
DAEMONS444
,E PROCESS DESC5DS F ,,PID #A  ! :OLE
SY/EM IS "O =K TREE4 ,SES.N "7 LOG9
3TEXT2 PROCESS-GR\P "7 A PIPEL9E'S JOBS2
3TROLL+-TTY "7 :AT ,CTRL-;,C T>GETS4
,! SIGNAL-S5D GRAMM>
KILL ,,PID             _? ,,SIGT]M #AE 
ASK POLITELY KILL -#I ,,PID          _?
,,SIGKILL  UNCAT*ABLE KILL -,,HUP ,,PID 
_? RELOAD  DAEMONS' 3V5;N KILL -,,9T
,,PID        _? ,CTRL-;,C EQUIVAL5T KILL
-,,T/P ,,PID       _? ,CTRL-;,Z
EQUIVAL5T KILL -,,3T ,,PID       _?
RESUME KILL -,,USR#A ,,PID       _?
APP'S PRIVATE TRI7]  NG9X RELOADS1 DD
PR9TS PROGRESS KILL -- -,,PGID        _?
A PROCESS ,,GR\P KILL -;L             
_? #A#CA /&>D "6 ,,SIGRTM944,,SIGRTMAX
R1L"T KILL -#J ,,PID          _? 8DOES X
EXI/80  ! PROBE KILLALL "N         _? BY
"N PKILL -;F PATT]N     _? BY CMDL9E
PKILL -;U ALICE       _? ALL ( ALICE'S
,! TWO UNCAT*ABLES3 ,,SIGKILL & ,,SIG/OP
! K]NEL'S GU>ANTEES T NO?+ C REFUSE D1?
OR SUSP5.N4 ,"EY?+ ELSE A PROCESS MAY
TRAP_/H&LE_/IGNORE4
KILL -#J IS ! EXI/;E PROBE  RETURNS !
]ROR )\T KILL+4 -,,USR#A IS ! 3V5;N APPS
USE = RELOAD_//ATUS  DD PR9TS XS
PROGRESS ON ,,USR#A4
_/PROC  ! PROCESS'S 9N>DS
LS _/PROC_/@S@S         _? ,,YR %ELL'S
PROCESS1 Z FILES CAT _/PROC_/@S@S_//ATUS
_? /ATE1 MEMORY1 UIDS CAT
_/PROC_/@S@S_/CMDL9E _\ TR '_*#J' ' '  
_? XS >GV LS -;L _/PROC_/@S@S_/FD      
_? XS OP5 FILES  ! FDS6 CAT
_/PROC_/@S@S_/5VIRON _\ TR '_*#J' '_*N' 
_? XS 5VIRON;T CAT _/PROC_/LOADAVG      
_? #A_/#E_/#AE-M9 LOAD "6 RUNN+_/TOTAL
CAT _/PROC_/MEM9FO       _? ! MEMORY
L$G] CAT _/PROC_/CPU9FO       _? !
,C,P,US
_/PROC_/,,PID_/FD_/ AL"O IS WOR? ! *APT]
E OP5 FILE1 SOCKET1 & PIPE Z A SYML9K4
LS( & LS -;L _/PROC_/"9_/FD %[ :O HOLDS
:AT4
,PRIORITIES  NICE & ! S*$UL]
NICE -;N #AJ CMD          _? RUN X NIC]
"<L[] PRIOR;Y1 -#BJ44#AI"> R5ICE "6#E
-;P ,,PID        _? *ANGE A RUNN+ "O PS
-O PID1NI1COMM       _? SEE NICE VALUES
,HI<] NICE "7 L[] PRIOR;Y  8NIC]0 TO
O!RS4 *RT1 IONICE1 TASKSET R1* ! DEEP]
S*$UL]S "<,,RT CLASSES1 ,I_/,O PRIOR;Y1
,,CPU P9N+">4
,RES\RCE LIMITS
ULIMIT -A               _? ? %ELL'S
LIMITS  FDS1 CORE SIZE1 PROCS1 MEMORY
ULIMIT -;N #DJIF          _? RAISE FD
CEIL+ CAT _/PROC_/,,PID_/LIMITS    _? A
RUNN+ PROCESS'S LIMITS "T\T #CJ CMD     
_? KILL AF #CJ;S  ! BLUNT 9/RU;T
SY/EMD'S
,LIMIT,N,P,R,O,C_/,LIMIT,N,O,F,I,L,E  !
S]VICE-LEVEL EQUIVAL5TS
ULIMIT -;N "<MAX OP5 FILES"> IS ! "O
Y';LL ACTUALLY HIT  BUSY S]V]S BUMP X
3/ANTLY4
,SIGNALS  ! COMPLETE TAXONOMY
KILL -;L                    _? #FD TOTAL
#A#CA /&>D1 #CB#FD R1L"T
"<,,SIGRTM944,,SIGRTMAX"> ,,SI<UP 
"<#A">   _? HANGUP  T]M9AL CLOS$ 
DAEMONS USE Z 8RELOAD 3FIG0 ,,SIG9T 
"<#B">   _? ,CTRL-;,C  9T]RUPT ,,SIGQUIT
"<#C">   _? ,CTRL-_*  QUIT "6 CORE DUMP
,,SIGILL  "<#D">   _? ILLEGAL 9/RUC;N
,,SIGTRAP "<#E">   _? DEBU7] BR1KPO9T
,,SIGABRT "<#F">   _? ABORT"<">  ! CORE
DUMP ,,SIGFPE  "<#H">   _? >I?METIC
FAULT  DIV BY Z]O ,,SIGKILL "<#I">   _?
,,UNCAT*ABLE  K]NEL KILLS X N[ ,,SIGSEGV
"<#AA">  _? SEGFAULT  BAD MEMORY A3ESS
,,SIGPIPE "<#AC">  _? WROTE TO A CLOS$
PIPE  ! 8BROK5 PIPE0 ,,SIGALRM "<#AD"> 
_? AL>M"<"> "TR ,,SIGT]M "<#AE">  _?
POLITE T]M9ATE  ! DEFAULT KILL ,,SIG*LD
"<#AG">  _? A * DI$  P>5T R1PS VIA
WAIT"<"> ,,SIGCONT "<#AH">  _? RESUME A
/OPP$ PROCESS ,,SIG/OP "<#AI">  _?
,,UNCAT*ABLE SUSP5D ,,SIGT/P "<#BJ">  _?
,CTRL-;,Z  T]M9AL /OP "<CAT*ABLE">
,,SIGUSR#A_/#B "<#AJ_/#AB">  _?
US]-DEF9$  DAEMONS' PRIVATE TRI7]S
,! SEMANTICS3 ,,SIGT]M ASKS "<CAT*ABLE 
A PROCESS C TRAP X & CL1N UP">2
,,SIGKILL EXECUTES "<UNCAT*ABLE  NO
CL1NUP POSSIBLE">2 ,,SI<UP IS OV]LOAD$ Z
8RELOAD YR 3FIG0 = DAEMONS2
,,SIG/OP_/,,SIGCONT >E ! DEBU7]'S & JOB
3TROL'S PAUSE_/RESUME4 TRAP CAT*ES !
CAT*ABLES  TRAP 'CL1NUP' ,,T]M ,,9T IS !
DAEMON-%UTD[N PATT]N4
,NUMB]S #CB#FD >E ! R1L"T RANGE3 #CB#CC
>E RES]V$ = GLIBC'S ?R1D+ 9T]NALS1 &
#CD#FD >E ,,SIGRTM944,,SIGRTMAX "<;,C3
,,SIGRTM9"6N">  SAME DELIV]Y1 B !Y QUEUE
"<MULTIPLE 9/.ES >5'T COALESC$"> & C
C>RY AN 9TEG] PAYLOAD  ,,POSIX "TRS1
,,AIO1 & MQ.-NOTIFY USE !M4 KILL
-,,RTM9"6#E ,,PID S5DS "O2 KILL -;L LI/S
ALL #FD SLOTS4
,SES.NS1 GR\PS1 & ! 3TROLL+ T]M9AL
PS -O PID1PPID1PGID1SID1TTY1CMD -;E _\
H1D   _? ! :OLE HI]>*Y SETSID CMD       
_? NEW SES.N  DETA* F ! T]M9AL 4[N .0#A 
_? DROP F JOB TABLE  SURVIVE EXIT NOHUP
CMD @&                _? ,,SI<UP-IMMUNE
,A SES.N "7 A LOG9 OR DETA*$ 3TEXT2 A
PROCESS GR\P "7 A PIPEL9E'S JOBS  KILL
-,,PID T>GETS A PID1 KILL -- -,,PGID A
GR\P4 ,! 3TROLL+ T]M9AL "<,,TTY 9 PS">
IS :AT ,CTRL-;,C SIGNALS HIT  DAEMONS %$
X VIA SETSID4
CGR\PS "6 "NSPACES  ! 3TA9] PRIMITIVES
LS _/SYS_/FS_/CGR\P_/           _? !
CGR\P HI]>*Y  ! R1L 3TA9] LAY] CAT
_/PROC_/,,PID_/CGR\P         _? A
PROCESS'S CGR\P SY/EMD-CGLS             
_? SY/EMD'S CGR\P TREE UN%>E -;U -;N -;P
BA%        _? A BA% 9 FRE% "NSPACES  A
PROTO-3TA9] LSNS                        
_? LI/ "NSPACES
,"NSPACES "<MNT1 PID1 NET1 IPC1 UTS1
US]"> ISOLATE2 CGR\PS MET] "<CPU1
MEMORY1 IO LIMITS">4 ,3TA9]S >E ^! TWO
PRIMITIVES >RANG$  DOCK] RUN "7 "NSPACES
"6 CGR\PS "6 AN IMAGE1 NO?+ M4
,! S*$UL]'S DEEP] KNOBS
NICE -;N #AJ CMD               _?
-#BJ44#AI  HI<] "7 ,,L[] PRIOR;Y R5ICE
-;N #E -;P ,,PID           _? LIVE-TUNE
*RT -;F #EJ CMD               _?
,,S*$.-,,FIFO R1L"T *RT -;R #EJ CMD     
_? ,,S*$.-,,RR IONICE -C#C CMD          
_? IO PRIOR;Y  IDLE-CLASS TASKSET -;C
#J1A CMD           _? ,,CPU P9N+
,R1L"T CLASSES B1T NICE 
,,S*$.-,,FIFO_/,,RR PREEMPT "EY?+ ELSE2
IONICE & TASKSET %APE ,I_/,O & ,,CPU
A69;Y4
,MONITOR+ 2Y TOP
VM/AT #A              _? MEMORY "6 ,,IO
"6 ,,CPU1 P] SECOND IO/AT -;X #A        
_? 4K ,I_/,O MP/AT -;,P ,,ALL #A      
_? P]-,,CPU D/AT                 _? !
"EY?+-MONITOR FREE -;H               _?
MEMORY N[ WAT* -N#A 'PS AUX
--SORT"7-.0CPU _\ H1D'   _? YR [N LIVE
MONITOR
,LOAD AV]AGE "<UP"T"> "7 RUNNABLE
PROCESSES AV]AG$ OV] #A_/#E_/#AE M9 
#D4JJ ON #D ,C,P,US "7 SATURAT$2 ON #H
,C,P,US "7 HALF-LOAD$4 ,9T]PRET RELATIVE
TO CORE C.T4
,": PROCESS "W GOES WR;G
,SYMPTOM  ,CAUSE   KILL DIDN'T KILL X 
,PROCESS IGNOR$ ,,SIGT]M  ESCALATE TO
-#I   KILL -#I DIDN'T KILL X  ;,D /ATE 
MID-SYSCALL1 (T5 D1D ,,NFS_/4K ,I_/,O  
,ZOMBIE PIL+ UP  ,P>5T N WAIT"<">9G  A
P>5T BUG2 KILL ! P>5T   ,DAEMON DIES AT
LOG\T  ,NE$$ NOHUP_/SETSID_/4[N  ,,SI<UP
,CTRL-;,C DOESN'T "W  ,PROCESS TRAPS OR
IGNORES ,,SIG9T   ,C'T F9D ! PROCESS  PS
-EF  GREP "N2 PGREP -;F = CMDL9E   8,TOO
_M OP5 FILES0  ULIMIT -;N  ! FD CEIL+
,EX]CISES
#A4 SLEEP #CJJ @&  JOB 3TROL3 JOBS1 FG1
,CTRL-;,Z1 BG1 KILL4 #B4 LS -;L
_/PROC_/@S@S_/FD  9SPECT YR %ELL'S [N
OP5 FILES4 #C4 BA% -;C 'SLEEP #II' !N PS
-EJ,H  F9D ! =K RELA;N%IP4 #D4 KILL
-,,T/P A PROCESS !N -,,3T  FREEZE & ?AW
X4 #E4 WAT* -N#A CAT _/PROC_/LOADAVG 
WAT* LOAD BR1!4 #F4 ULIMIT -;N  YR FD
CEIL+2 !N RAISE X & NOTE ": X MATT]S4
,"TL9E
,3CEPT  ,ME*ANISM   ,BIR?  =K"<"> 
EXEC"<">   ,D1?  EXIT"<">  ZOMBIE 
WAIT"<">   ,,PID #A  ,! ANCE/OR ( ALL 
SY/EMD_/,SYS,V9IT   ,SIGNALS 
,9T]-PROCESS 9T]RUPTS   _/PROC  ,!
K]NEL'S PROCESS W9D[ ,SEE AL
- ,L9UX  ,%ELL  ,CORE ,UTILITIES  ,,LFS
,K]NEL & ,BOOT