kill -9 PID 是操作系统从内核级别强制杀死一个进程。
kill -15 PID 可以理解为操作系统发送一个通知告诉应用主动关闭。
kill -15 PID 效果是正常退出进程,退出前可以被阻塞或回调处理。并且它是Linux缺省的程序中断信号。
尽量使用kill -15 PID而不要使用kill -9 PID
kill -9 PID没有给进程留下善后的机会:
1) 关闭socket链接
2) 清理临时文件
3) 将自己将要被销毁的消息通知给子进程
4) 重置自己的终止状态
等等。
一些磁盘操作多的程序更是不要使用kill -9 PID,会导致数据的丢失,如ES,kafka等。
kill -l(查看Linux/Unix的信号变量)
linux signals
Signal Name | Number | Description |
SIGHUP | 1 | Hangup (POSIX) |
SIGINT | 2 | Terminal interrupt (ANSI) |
SIGQUIT | 3 | Terminal quit (POSIX) |
SIGILL | 4 | Illegal instruction (ANSI) |
SIGTRAP | 5 | Trace trap (POSIX) |
SIGIOT | 6 | IOT Trap (4.2 BSD) |
SIGBUS | 7 | BUS error (4.2 BSD) |
SIGFPE | 8 | Floating point exception (ANSI) |
SIGKILL | 9 | Kill(can't be caught or ignored) (POSIX) |
SIGUSR1 | 10 | User defined signal 1 (POSIX) |
SIGSEGV | 11 | Invalid memory segment access (ANSI) |
SIGUSR2 | 12 | User defined signal 2 (POSIX) |
SIGPIPE | 13 | Write on a pipe with no reader, Broken pipe (POSIX) |
SIGALRM | 14 | Alarm clock (POSIX) |
SIGTERM | 15 | Termination (ANSI) |
SIGSTKFLT | 16 | Stack fault |
SIGCHLD | 17 | Child process has stopped or exited, changed (POSIX) |
SIGCONT | 18 | Continue executing, if stopped (POSIX) |
SIGSTOP | 19 | Stop executing(can't be caught or ignored) (POSIX) |
SIGTSTP | 20 | Terminal stop signal (POSIX) |
SIGTTIN | 21 | Background process trying to read, from TTY (POSIX) |
SIGTTOU | 22 | Background process trying to write, to TTY (POSIX) |
SIGURG | 23 | Urgent condition on socket (4.2 BSD) |
SIGXCPU | 24 | CPU limit exceeded (4.2 BSD) |
SIGXFSZ | 25 | File size limit exceeded (4.2 BSD) |
SIGVTALRM | 26 | Virtual alarm clock (4.2 BSD) |
SIGPROF | 27 | Profiling alarm clock (4.2 BSD) |
SIGWINCH | 28 | Window size change (4.3 BSD, Sun) |
SIGIO | 29 | I/O now possible (4.2 BSD) |
SIGPWR | 30 | Power failure restart (System V) |