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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

       fuser — list process IDs of all processes that have one or more files open

SYNOPSIS

       fuser [-cfu] file...

DESCRIPTION

       The  fuser  utility shall write to standard output the process IDs of processes running on
       the local system that have one or more named files open.  For block special  devices,  all
       processes using any file on that device are listed.

       The  fuser  utility  shall  write to standard error additional information about the named
       files indicating how the file is being used.

       Any output for processes running on  remote  systems  that  have  a  named  file  open  is
       unspecified.

       A user may need appropriate privileges to invoke the fuser utility.

OPTIONS

       The  fuser  utility  shall conform to the Base Definitions volume of POSIX.1‐2017, Section
       12.2, Utility Syntax Guidelines.

       The following options shall be supported:

       -c        The file is treated as a mount point and the utility shall report on  any  files
                 open in the file system.

       -f        The report shall be only for the named files.

       -u        The  user  name,  in  parentheses,  associated  with  each process ID written to
                 standard output shall be written to standard error.

OPERANDS

       The following operand shall be supported:

       file      A pathname on which the file or file system is to be reported.

STDIN

       Not used.

INPUT FILES

       The user database.

ENVIRONMENT VARIABLES

       The following environment variables shall affect the execution of fuser:

       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

       The  fuser utility shall write the process ID for each process using each file given as an
       operand to standard output in the following format:

           "%d", <process_id>

STDERR

The fuser utility shall write diagnostic messages to standard error.

The fuser utility also shall write the following to standard error:

* The pathname of each named file is written followed immediately by a <colon>.

* For each process ID written to standard output, the character 'c' shall be written to
standard error if the process is using the file as its current directory and the
character 'r' shall be written to standard error if the process is using the file as
its root directory. Implementations may write other alphabetic characters to indicate
other uses of files.

* When the -u option is specified, characters indicating the use of the file shall be
followed immediately by the user name, in parentheses, corresponding to the real user
ID of the process. If the user name cannot be resolved from the real user ID of the
process, the real user ID of the process shall be written instead of the user name.

When standard output and standard error are directed to the same file, the output shall be
interleaved so that the filename appears at the start of each line, followed by the
process ID and characters indicating the use of the file. Then, if the -u option is
specified, the user name or user ID for each process using that file shall be written.

A <newline> shall be written to standard error after the last output described above for
each file operand.

OUTPUT FILES

       None.

EXTENDED DESCRIPTION

       None.

EXIT STATUS

       The following exit values shall be returned:

        0    Successful completion.

       >0    An error occurred.

CONSEQUENCES OF ERRORS

       Default.

       The following sections are informative.

APPLICATION USAGE

       None.

EXAMPLES

       The command:

           fuser -fu .

       writes  to  standard  output  the  process  IDs  of  processes  that are using the current
       directory and writes to standard error an indication of how those processes are using  the
       directory  and  the  user  names  associated with the processes that are using the current
       directory.

           fuser -c <mount point>

       writes to standard output the process IDs of processes that are using any file in the file
       system which is mounted on <mount point> and writes to standard error an indication of how
       those processes are using the files.

           fuser <mount point>

       writes to standard output the process IDs of processes that are using the  file  which  is
       named  by  <mount point> and writes to standard error an indication of how those processes
       are using the file.

           fuser <block device>

       writes to standard output the process IDs of processes that are using any file which is on
       the device named by <block device> and writes to standard error an indication of how those
       processes are using the file.

           fuser -f <block device>

       writes to standard output the process IDs of processes that  are  using  the  file  <block
       device> itself and writes to standard error an indication of how those processes are using
       the file.

RATIONALE

       The definition of the fuser utility follows existing practice.

FUTURE DIRECTIONS

       None.

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 .