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PROLOG | NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OPERANDS | STDIN | INPUT FILES | ENVIRONMENT VARIABLES | ASYNCHRONOUS EVENTS | STDOUT | STDERR | OUTPUT FILES | EXTENDED DESCRIPTION | EXIT STATUS | CONSEQUENCES OF ERRORS | APPLICATION USAGE | EXAMPLES | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
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FUSER(1P) POSIX Programmer's Manual FUSER(1P)
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.
fuser — list process IDs of all processes that have one or more
files open
fuser [-cfu] file...
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.
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.
The following operand shall be supported:
file A pathname on which the file or file system is to be
reported.
Not used.
The user database.
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.
Default.
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>
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.
None.
None.
The following exit values shall be returned:
0 Successful completion.
>0 An error occurred.
Default.
The following sections are informative.
None.
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.
The definition of the fuser utility follows existing practice.
None.
The Base Definitions volume of POSIX.1‐2017, Chapter 8,
Environment Variables, Section 12.2, Utility Syntax Guidelines
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 .
IEEE/The Open Group 2017 FUSER(1P)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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