The Single UNIX ® Specification, Version 2
Copyright © 1997 The Open Group


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


fuser [ -cfu ] file ...


The fuser utility writes 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 writes 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 privilege to invoke the fuser utility.


The fuser utility supports the XBD specification, Utility Syntax Guidelines  .

The following options are supported:

The file is treated as a mount point and the utility reports on any files open in the file system.
The report is only for the named files.
The user name, in parentheses, associated with each process ID written to standard output is written to standard error.


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


Not used.


The user database.


The following environment variables affect the execution of fuser:
Provide a default value for the internationalization variables that are unset or null. If LANG is unset or null, the corresponding value from the implementation-dependent default locale will be used. If any of the internationalization variables contain an invalid setting, the utility will behave as if none of the variables had been set.
If set to a non-empty string value, override the values of all the other internationalization variables.
Determine the locale for the interpretation of sequences of bytes of text data as characters (for example, single- as opposed to multi-byte characters in arguments).
Determine the locale that should be used to affect the format and contents of diagnostic messages written to standard error.
Determine the location of message catalogues for the processing of LC_MESSAGES .




The fuser utility will 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 writes diagnostic messages to standard error.

The fuser utility also writes the following to standard error:

When standard output and standard error are directed to the same file, the output is interspersed 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 is written.

A new line character is written to standard error after the last output described above for each file operand.






The following exit values are returned:
Successful completion.
An error occurred.






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.





UNIX ® is a registered Trademark of The Open Group.
Copyright © 1997 The Open Group
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