Por favor, explique esta saída do comando ps -ef?

Question

Uma parte da saída do comando ps -ef é fornecida abaixo:

UID        PID  PPID  C STIME TTY          TIME CMD
root         1     0  0  2012 ?        00:00:01 init [3]         
root         2     1  0  2012 ?        00:00:01 [migration/0]
root         3     1  0  2012 ?        00:00:00 [ksoftirqd/0]
root         4     1  0  2012 ?        00:00:00 [watchdog/0]
root         5     1  0  2012 ?        00:00:00 [events/0]
root         6     1  0  2012 ?        00:00:00 [khelper]
root         7     1  0  2012 ?        00:00:00 [kthread]
root         9     7  0  2012 ?        00:00:00 [xenwatch]
root        10     7  0  2012 ?        00:00:00 [xenbus]
root        18     7  0  2012 ?        00:00:01 [migration/1]
root        19     7  0  2012 ?        00:00:00 [ksoftirqd/1]

O que significa o "?" para todas as linhas na coluna TTY? Além disso, o que significa C e CMD coluna?

    

Answer 1

Você pode verificar a manpage usando man ps para descobrir o que as colunas significam. O Linux ps manpage, por exemplo, fornece:

c              C           integer value of the processor utilisation percentage.
                           (see %cpu)
tname          TTY         controlling tty (terminal). (alias tt, tty).
args           COMMAND     command with all its arguments as a string. May chop as
                           desired. Modifications to the arguments are not shown.
                           The output in this column may contain spaces.
                           (alias cmd, command)
cmd            CMD         see args. (alias args, command)

Se o TTY for ? , isso significa que o processo não está associado a nenhum terminal de usuário.

    

Answer 2

Como esses são todos os processos do kernel, eles não são anexados a um TTY (daí o valor ? no campo TTY ).

    

Answer 3

Exemplos de alguns cabeçalhos

F   S   UID     ID  PPID C  PRI NI  ADDR        SZ  WCHAN   STIME   TTY    TIME COMD

1   R   obiwan  792 779 22  183 20  10ec5f80    29    -    12:52:24 pts/2   0:00    ps -elf

Explicação

ColumnHeader    Contents
%CPU            How much of the CPU the process is using
%MEM            How much memory the process is using
ADDR            Memory address of the process
C or CP         CPU usage and scheduling information
COMMAND*        Name of the process, including arguments, if any
NI              nice value
F               Flags
PID             Process ID number
PPID            ID number of the process's parent process
PRI             Priority of the process
RSS             Real memory usage
S or STAT       Process status code
START or STIME  Time when the process started
SZ              Virtual memory usage
TIME            Total CPU usage
TT or TTY       Terminal associated with the process
UID or USER     Username of the process's owner
WCHAN           Memory address of the event the process is waiting for

Créditos: Base de Conhecimento da Universidade de Indiana