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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.1‐2008,  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.1‐2008, 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, 2013 Edition,
       Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open  Group  Base
       Specifications  Issue 7, Copyright (C) 2013 by the Institute of Electrical and Electronics Engineers, Inc
       and The Open Group.  (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) 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.unix.org/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 .