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    fuser – identify processes using files or sockets 确认进程使用的文件或套接字

           fuser  displays  the  PIDs  of processes using the specified files or file systems.  In the default display mode, each file name is followed by a letter   denoting the type of access:       fuser  用来显示访问指定文件或文件系统的PID,在默认情况下,在每个PID后边都有一个字符,用来显示访问方式

                  c      current directory.         表示该PID在访问的是该目录

                  e      executable being run. 表示该PID是一个可执行文件

                  f      open file. f is omitted in default display mode. 表示该PID是一个打开的文件,默认不显示

                  F      open file for writing. F is omitted in default display mode. 表示该PID是一个打开准备写入的文件,默认不显示

                  r      root directory.  根目录,表示该目录是该PID的根目录

                  m      mmap’ed file or shared library 表示该PID是mmap的目录或是一个共享库

    fuser returns a non-zero return code if none of the specified files is accessed or in case of a fatal error. If at least  one  access  has  been  found,       fuser returns zero.
           In  order to look up processes using TCP and UDP sockets, the corresponding name space has to be selected with the -n option. By default fuser will look  in both IPv6 and IPv4 sockets. To change the default, behavior, use the -4 and -6 options. The socket(s) can be specified by the local and remote  port,  and the remote address. All fields are optional, but commas in front of missing fields must be present:

           Either symbolic or numeric values can be used for IP addresses and port numbers.
           fuser outputs only the PIDs to stdout, everything else is sent to stderr.

           -a     Show all files specified on the  command  line.  By
                  default,  only  files that are accessed by at least
                  one process are shown.

           -c     Same as -m option, used for POSIX compatibility.
           -f     Silently ignored, used for POSIX compatibility.
           -k     Kill processes accessing the file.  Unless  changed  with  -signal,  SIGKILL  is  sent. An fuser process never kills itself, but may kill other  fuser  pro- cesses.  The  effective user ID of the process exe- cuting fuser is set to  its  real  user  ID  before   attempting to kill.
           -i     Ask the user for confirmation before killing a pro- cess. This option is silently ignored if -k is  not    present too.
         -l     List all known signal names.
           -m     name specifies a file on a mounted file system or a  block device that is mounted. All processes access- ing  files  on  that  file system are listed.  If a  directory file is specified,  it  is  automatically   changed to name/. to use any file system that might  be mounted on that directory.
           -n space
                  Select a different name space. The name spaces file  (file  names,  the default), udp (local UDP ports),   and tcp (local TCP ports) are supported. For ports, either  the port number or the symbolic name can be  specified. If there is no ambiguity,  the  shortcut   notation name/Ispace (e.g. 80/tcp ) can be used.
    设置一个不同的命名空间。命名空间可以使文件(默认),udp(本地udp端口),和tcp(本地tcp端口)。对于端口,可以是数字端口,也可以是一个别名。你甚至可以使用 ‘<port>/<proto>’ 的方式,只要不存在异义的话
           -s     Silent  operation.  -u  and  -v are ignored in this
                  mode.  -a must not be used with -s.

                  Use  the  specified signal instead of SIGKILL when killing processes. Signals can be specified either by name (e.g. -HUP) or by number (e.g. -1).
                  This option is silently ignored if the -k option is not used.
           -u     Append the user name of the process owner to each PID.
           -v     Verbose mode. Processes are shown in a ps-like style. The fields PID, USER and COMMAND are similar to ps. ACCESS shows how the  process  accesses
                  the file. If the access is by the kernel (e.g. in the case of a mount point, a swap file, etc.), kernel is shown instead of the PID.
    冗长模式。进程以ps的模式显示。 PID,USERS和COMMAND同ps显示的相同。ACCESS显示存取文件的状态,如果是内核访问的(例如挂载点或交换分区的文件),则显示kernel而不是PID。
           -V     Display version information.
           -4     Search only for IPv4 sockets. This option must not be used with the -6 option and only has an effect with the tcp and udp namespaces.
           -6     Search only for IPv6 sockets. This option must not be used with the -4 option and only has an effect with the tcp and udp namespaces.
           –      Reset all options and set the signal back to SIGKILL.
    ‘-’ 表示重置所有选项并把信号设置为 SIGKILL
           /proc     location of the proc file system

           fuser -km /home kills all processes accessing the file system /home in any way.
    fuser -km /home 杀死所有存取/home文件系统的进程。
           if fuser -s /dev/ttyS1; then :; else something; fi invokes something if no other process is using /dev/ttyS1.

           fuser telnet/tcp shows all processes at the (local) TELNET port.
    fuser telnet/tcp显示所有在本地telnet端口的进程。
           Processes accessing the same file or file system several times in the same way are only shown once.
           If the same object is specified several times on the command line, some of those entries may be ignored.
          fuser  may  only  be able to gather partial information unless run with privileges. As a consequence, files opened by processes belonging to other users   may not be listed and executables may be classified as mapped only.

          Installing fuser SUID root will avoid problems associated with partial information, but may be undesirable for security and privacy reasons.

           udp and tcp name spaces, and UNIX domain sockets can’t be searched with kernels older than 1.3.78.
           1.3.78以前的内核不能搜索udp,tcp,和unix 域套接字的pid。
           udp and tcp currently  work with IPv6 and IPv4, but the address fields can only be IPv4 addresses.
           Accesses by the kernel are only shown with the -v option.
           The -k option only works on processes. If the user is the kernel, fuser will print an advice, but take no action beyond that.