| fuser—identifies processes using files or sockets
fuser [-a|-s] [-n space] [-signal] [-kmuv] name ...[-] [-n space]
   [-signal] [-kmuv] name ...
fuser -l
fuser -V
 
 The fuser command displays the PIDs of processes using the specified file or filesystems. In the default display mode, each filename is followed by a letter denoting the type of access. Example A.31. 
% fuser --help
usage: fuser [ -a | -q ] [ -n space ] [ -signal ] [ -kmuv ]
filename ... [ - ] [ -n space ] [ -signal ] [ -kmuv ] name
...
       fuser -l
       fuser -V
    -a        display unused files too
    -k        kill processes accessing that file
    -l        list signal names
    -m        mounted FS
    -n        space  search in the specified name space (file, udp, or tcp)
    -s        silent operation
    -signal   send signal instead of SIGKILL
    -u        display user ids
    -v        verbose output
    -V        display version information
    -         reset options
  udp/tcp names: [local_port][,[rmt_host][,[rmt_port]]]
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