kill命令

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命令用途

kill 是 Linux/Unix 系统中用于向进程发送信号的命令，默认发送 SIGTERM（终止信号），常用于终止或控制进程的运行状态。

常用用法示例

1. 终止指定PID的进程

   kill 1234  

   向进程ID为1234的进程发送默认信号SIGTERM（15），请求其正常退出。若进程响应，则无输出；若失败会提示错误（如权限不足或进程不存在）。

2. 强制终止进程

   kill -9 1234  

   发送SIGKILL信号（编号9），强制立即终止PID为1234的进程。无输出表示操作成功。

3. 终止进程并显示操作结果

   kill -v 1234  
   kill: 1234: No such process 

   -v参数会显示操作结果，若进程不存在则提示错误。

4. 向进程发送挂起信号

   kill -HUP 1234  

   发送SIGHUP信号（1），常用于通知进程重新加载配置文件（如Nginx）。

5. 终止进程组

   kill -9 -1234  

   向进程组ID为1234的所有进程发送SIGKILL，负号表示操作进程组。

6. 列出所有支持的信号名称

   kill -l  
   1) SIGHUP   2) SIGINT   3) SIGQUIT  4) SIGILL   5) SIGTRAP 
   ...  

   显示系统支持的信号列表及其编号。

7. 使用信号名称发送信号

   kill -s SIGUSR1 1234  

   向PID为1234的进程发送自定义信号SIGUSR1，常用于进程间通信。

8. 批量终止多个进程

   kill -9 1234 5678 9012  

   同时强制终止PID为1234、5678、9012的多个进程。

常用参数选项

• -9, -SIGKILL
  强制立即终止进程，进程无法捕获或忽略此信号。

• -15, -SIGTERM
  默认信号，请求进程正常终止（允许进程清理资源）。

• -l, –list
  列出所有支持的信号名称及编号。

• -s, –signal
  指定信号名称或编号（如-s SIGINT或-s 2）。

• -HUP, -1
  发送挂起信号，常用于通知守护进程重新加载配置。

• -INT, -2
  发送中断信号（等同于Ctrl+C），通常用于终止前台进程。

• -QUIT, -3
  发送退出信号（等同于Ctrl+\），终止进程并生成核心转储文件。

• -USER1, -USR1
  发送用户自定义信号1，可用于触发进程自定义操作（如日志轮转）。

原厂文档

PROLOG 

       This manual page is part of the POSIX Programmer's Manual.  The
       Linux implementation of this interface may differ (consult the
       corresponding Linux manual page for details of Linux behavior), or
       the interface may not be implemented on Linux.

NAME 

       kill — terminate or signal processes

SYNOPSIS 

       kill -s signal_name pid...

       kill -l [exit_status]

       kill [-signal_name] pid...

       kill [-signal_number] pid...

DESCRIPTION 

       The kill utility shall send a signal to the process or processes
       specified by each pid operand.

       For each pid operand, the kill utility shall perform actions
       equivalent to the kill() function defined in the System Interfaces
       volume of POSIX.1‐2017 called with the following arguments:

        *  The value of the pid operand shall be used as the pid
           argument.

        *  The sig argument is the value specified by the -s option,
           -signal_number option, or the -signal_name option, or by
           SIGTERM, if none of these options is specified.

OPTIONS 

       The kill utility shall conform to the Base Definitions volume of
       POSIX.1‐2017, Section 12.2, Utility Syntax Guidelines, except that
       in the last two SYNOPSIS forms, the -signal_number and
       -signal_name options are usually more than a single character.

       The following options shall be supported:

       -l        (The letter ell.) Write all values of signal_name
                 supported by the implementation, if no operand is given.
                 If an exit_status operand is given and it is a value of
                 the '?'  shell special parameter (see Section 2.5.2,
                 Special Parameters and wait) corresponding to a process
                 that was terminated by a signal, the signal_name
                 corresponding to the signal that terminated the process
                 shall be written. If an exit_status operand is given and
                 it is the unsigned decimal integer value of a signal
                 number, the signal_name (the symbolic constant name
                 without the SIG prefix defined in the Base Definitions
                 volume of POSIX.1‐2017) corresponding to that signal
                 shall be written. Otherwise, the results are
                 unspecified.

       -s signal_name
                 Specify the signal to send, using one of the symbolic
                 names defined in the <signal.h> header. Values of
                 signal_name shall be recognized in a case-independent
                 fashion, without the SIG prefix. In addition, the
                 symbolic name 0 shall be recognized, representing the
                 signal value zero. The corresponding signal shall be
                 sent instead of SIGTERM.

       -signal_name
                 Equivalent to -s signal_name.

       -signal_number
                 Specify a non-negative decimal integer, signal_number,
                 representing the signal to be used instead of SIGTERM,
                 as the sig argument in the effective call to kill().
                 The correspondence between integer values and the sig
                 value used is shown in the following list.

                 The effects of specifying any signal_number other than
                 those listed below are undefined.

                 0     0

                 1     SIGHUP

                 2     SIGINT

                 3     SIGQUIT

                 6     SIGABRT

                 9     SIGKILL

                 14    SIGALRM

                 15    SIGTERM

                 If the first argument is a negative integer, it shall be
                 interpreted as a -signal_number option, not as a
                 negative pid operand specifying a process group.

OPERANDS 

       The following operands shall be supported:

       pid       One of the following:

                  1. A decimal integer specifying a process or process
                     group to be signaled.  The process or processes
                     selected by positive, negative, and zero values of
                     the pid operand shall be as described for the kill()
                     function. If process number 0 is specified, all
                     processes in the current process group shall be
                     signaled. For the effects of negative pid numbers,
                     see the kill() function defined in the System
                     Interfaces volume of POSIX.1‐2017. If the first pid
                     operand is negative, it should be preceded by "--"
                     to keep it from being interpreted as an option.

                  2. A job control job ID (see the Base Definitions
                     volume of POSIX.1‐2017, Section 3.204, Job Control
                     Job ID) that identifies a background process group
                     to be signaled. The job control job ID notation is
                     applicable only for invocations of kill in the
                     current shell execution environment; see Section
                     2.12, Shell Execution Environment.

       exit_status
                 A decimal integer specifying a signal number or the exit
                 status of a process terminated by a signal.

STDIN 

       Not used.

INPUT FILES 

       None.

ENVIRONMENT VARIABLES 

       The following environment variables shall affect the execution of
       kill:

       LANG      Provide a default value for the internationalization
                 variables that are unset or null. (See the Base
                 Definitions volume of POSIX.1‐2017, Section 8.2,
                 Internationalization Variables for the precedence of
                 internationalization variables used to determine the
                 values of locale categories.)

       LC_ALL    If set to a non-empty string value, override the values
                 of all the other internationalization variables.

       LC_CTYPE  Determine the locale for the interpretation of sequences
                 of bytes of text data as characters (for example,
                 single-byte as opposed to multi-byte characters in
                 arguments).

       LC_MESSAGES
                 Determine the locale that should be used to affect the
                 format and contents of diagnostic messages written to
                 standard error.

       NLSPATH   Determine the location of message catalogs for the
                 processing of LC_MESSAGES.

ASYNCHRONOUS EVENTS 

       Default.

STDOUT 

       When the -l option is not specified, the standard output shall not
       be used.

       When the -l option is specified, the symbolic name of each signal
       shall be written in the following format:

           "%s%c", <signal_name>, <separator>

       where the <signal_name> is in uppercase, without the SIG prefix,
       and the <separator> shall be either a <newline> or a <space>.  For
       the last signal written, <separator> shall be a <newline>.

       When both the -l option and exit_status operand are specified, the
       symbolic name of the corresponding signal shall be written in the
       following format:

           "%s\n", <signal_name>

STDERR 

       The standard error shall be used only for diagnostic messages.

OUTPUT FILES 

       None.

EXTENDED DESCRIPTION 

       None.

EXIT STATUS 

       The following exit values shall be returned:

        0    At least one matching process was found for each pid
             operand, and the specified signal was successfully processed
             for at least one matching process.

       >0    An error occurred.

CONSEQUENCES OF ERRORS 

       Default.

       The following sections are informative.

APPLICATION USAGE 

       Process numbers can be found by using ps.

       The job control job ID notation is not required to work as
       expected when kill is operating in its own utility execution
       environment. In either of the following examples:

           nohup kill %1 &
           system("kill %1");

       the kill operates in a different environment and does not share
       the shell's understanding of job numbers.

EXAMPLES 

       Any of the commands:

           kill -9 100 -165
           kill -s kill 100 -165
           kill -s KILL 100 -165

       sends the SIGKILL signal to the process whose process ID is 100
       and to all processes whose process group ID is 165, assuming the
       sending process has permission to send that signal to the
       specified processes, and that they exist.

       The System Interfaces volume of POSIX.1‐2017 and this volume of
       POSIX.1‐2017 do not require specific signal numbers for any
       signal_names.  Even the -signal_number option provides symbolic
       (although numeric) names for signals. If a process is terminated
       by a signal, its exit status indicates the signal that killed it,
       but the exact values are not specified. The kill -l option,
       however, can be used to map decimal signal numbers and exit status
       values into the name of a signal. The following example reports
       the status of a terminated job:

           job
           stat=$?
           if [ $stat -eq 0 ]
           then
               echo job completed successfully.
           elif [ $stat -gt 128 ]
           then
               echo job terminated by signal SIG$(kill -l $stat).
           else
               echo job terminated with error code $stat.
           fi

       To send the default signal to a process group (say 123), an
       application should use a command similar to one of the following:

           kill -TERM -123
           kill -- -123

RATIONALE 

       The -l option originated from the C shell, and is also implemented
       in the KornShell. The C shell output can consist of multiple
       output lines because the signal names do not always fit on a
       single line on some terminal screens. The KornShell output also
       included the implementation-defined signal numbers and was
       considered by the standard developers to be too difficult for
       scripts to parse conveniently. The specified output format is
       intended not only to accommodate the historical C shell output,
       but also to permit an entirely vertical or entirely horizontal
       listing on systems for which this is appropriate.

       An early proposal invented the name SIGNULL as a signal_name for
       signal 0 (used by the System Interfaces volume of POSIX.1‐2017 to
       test for the existence of a process without sending it a signal).
       Since the signal_name 0 can be used in this case unambiguously,
       SIGNULL has been removed.

       An early proposal also required symbolic signal_names to be
       recognized with or without the SIG prefix. Historical versions of
       kill have not written the SIG prefix for the -l option and have
       not recognized the SIG prefix on signal_names.  Since neither
       applications portability nor ease-of-use would be improved by
       requiring this extension, it is no longer required.

       To avoid an ambiguity of an initial negative number argument
       specifying either a signal number or a process group, POSIX.1‐2008
       mandates that it is always considered the former by
       implementations that support the XSI option. It also requires that
       conforming applications always use the "--" options terminator
       argument when specifying a process group, unless an option is also
       specified.

       The -s option was added in response to international interest in
       providing some form of kill that meets the Utility Syntax
       Guidelines.

       The job control job ID notation is not required to work as
       expected when kill is operating in its own utility execution
       environment. In either of the following examples:

           nohup kill %1 &
           system("kill %1");

       the kill operates in a different environment and does not
       understand how the shell has managed its job numbers.

FUTURE DIRECTIONS 

       None.

SEE ALSO 

       Chapter 2, Shell Command Language, ps(1p), wait(1p)

       The Base Definitions volume of POSIX.1‐2017, Section 3.204, Job
       Control Job ID, Chapter 8, Environment Variables, Section 12.2,
       Utility Syntax Guidelines, signal.h(0p)

       The System Interfaces volume of POSIX.1‐2017, kill(3p)

COPYRIGHT 

       Portions of this text are reprinted and reproduced in electronic
       form from IEEE Std 1003.1-2017, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The
       Open Group Base Specifications Issue 7, 2018 Edition, Copyright
       (C) 2018 by the Institute of Electrical and Electronics Engineers,
       Inc and The Open Group.  In the event of any discrepancy between
       this version and the original IEEE and The Open Group Standard,
       the original IEEE and The Open Group Standard is the referee
       document. The original Standard can be obtained online at
       http://www.opengroup.org/unix/online.html .

       Any typographical or formatting errors that appear in this page
       are most likely to have been introduced during the conversion of
       the source files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .