kill和kill -9

很多时候，会有人建议你，如果kill杀不掉一个进程，就用kill -9. 为什么？
kill是Linux下常见的命令。其man手册的功能定义如下：

kill – send a signal to a process

明朗了，其实kill就是给某个进程id发送了一个信号。默认发送的信号是SIGTERM，而kill -9发送的信号是SIGKILL，即exit。exit信号不会被系统阻塞，所以kill -9能顺利杀掉进程。当然你也可以使用kill发送其他信号给进程。
经常使用的killall呢？

killall – kill processes by name

即，通过指定进程名的方式杀死进程。

 

 

 

KILL(1)                    Linux User's Manual                   KILL(1)

NAME
       kill - send a signal to a process

SYNOPSIS
       kill [ -signal | -s signal ] pid ...
       kill [ -L | -V, --version ]
       kill -l  [ signal ]

DESCRIPTION
       The  default signal for kill is TERM. Use -l or -L to list avail‐
       able signals.  Particularly  useful  signals  include  HUP,  INT,
       KILL,  STOP,  CONT, and 0.  Alternate signals may be specified in
       three ways: -9 -SIGKILL -KILL.  Negative PID values may  be  used
       to choose whole process groups; see the PGID column in ps command
       output. A PID of -1 is special; it indicates all processes except
       the kill process itself and init.

SIGNALS
       The  signals  listed  below  may  be available for use with kill.
       When known constant, numbers and default behavior are shown.

       Name     Num   Action    Description
       0          0   n/a       exit code indicates if a signal may be sen
t
       ALRM      14   exit
       HUP        1   exit
       INT        2   exit
       KILL       9   exit      cannot be blocked
       PIPE      13   exit
       POLL           exit
       PROF           exit
       TERM      15   exit
       USR1           exit
       USR2           exit
       VTALRM         exit
       STKFLT         exit      might not be implemented
       PWR            ignore    might exit on some systems
       WINCH          ignore
       CHLD           ignore
       URG            ignore
       TSTP           stop      might interact with the shell
       TTIN           stop      might interact with the shell
       TTOU           stop      might interact with the shell
       STOP           stop      cannot be blocked
       CONT           restart   continue if stopped, otherwise ignore
       ABRT       6   core
       FPE        8   core
       ILL        4   core
       QUIT       3   core
       SEGV      11   core
       TRAP       5   core
       SYS            core      might not be implemented
       EMT            core      might not be implemented
       BUS            core      core dump might fail
       XCPU           core      core dump might fail
       XFSZ           core      core dump might fail

NOTES
       Your shell (command line interpreter) may have  a  built-in  kill
       command.   You  may  need  to  run  the command described here as
       /bin/kill to solve the conflict.

EXAMPLES
       kill -9 -1
              Kill all processes you can kill.

       kill -l 11
              Translate number 11 into a signal name.

       kill -L
              List the available signal choices in a nice table.

       kill 123 543 2341 3453
              Send the default signal, SIGTERM, to all those processes.

SEE ALSO
       pkill(1), skill(1), kill(2), renice(1), nice(1), signal(7),  kil‐
       lall(1).

STANDARDS
       This  command  meets appropriate standards. The -L flag is Linux-
       specific.

AUTHOR
       Albert  Cahalan  <[e-mail]>  wrote  kill  in  1999  to
       replace  a  bsdutils  one  that  was not standards compliant. The
       util-linux one might also work correctly.

       Please send bug reports to <[e-mail]>

Linux                       November 21, 1999                    KILL(1)

 

 

 

 

kill -l
 1) SIGHUP  2) SIGINT  3) SIGQUIT  4) SIGILL  5) SIGTRAP
 6) SIGABRT  7) SIGBUS  8) SIGFPE  9) SIGKILL 10) SIGUSR1
11) SIGSEGV 12) SIGUSR2 13) SIGPIPE 14) SIGALRM 15) SIGTERM
16) SIGSTKFLT 17) SIGCHLD 18) SIGCONT 19) SIGSTOP 20) SIGTSTP
21) SIGTTIN 22) SIGTTOU 23) SIGURG 24) SIGXCPU 25) SIGXFSZ
26) SIGVTALRM 27) SIGPROF 28) SIGWINCH 29) SIGIO 30) SIGPWR
31) SIGSYS 34) SIGRTMIN 35) SIGRTMIN+1 36) SIGRTMIN+2 37) SIGRTMIN+3
38) SIGRTMIN+4 39) SIGRTMIN+5 40) SIGRTMIN+6 41) SIGRTMIN+7 42) SIGRTMIN+8
43) SIGRTMIN+9 44) SIGRTMIN+10 45) SIGRTMIN+11 46) SIGRTMIN+12 47) SIGRTMIN+13
48) SIGRTMIN+14 49) SIGRTMIN+15 50) SIGRTMAX-14 51) SIGRTMAX-13 52) SIGRTMAX-12
53) SIGRTMAX-11 54) SIGRTMAX-10 55) SIGRTMAX-9 56) SIGRTMAX-8 57) SIGRTMAX-7
58) SIGRTMAX-6 59) SIGRTMAX-5 60) SIGRTMAX-4 61) SIGRTMAX-3 62) SIGRTMAX-2
63) SIGRTMAX-1 64) SIGRTMAX