---
name: "fuser"
section: "1"
platform: "openbsd"
package: "man"
version: "8.0-current-20261101"
release: "OpenBSD 8.0-current (2026-11-01)"
platforms: ["linux", "freebsd", "openbsd", "macos"]
url: "https://new.carta.tech/fuser"
---

# fuser(1)

identify process IDs holding specific files open

## NAME

**fuser** – identify process IDs holding specific files open

## SYNOPSIS

**fuser** \[**-cfku**\] \[**-M** *core*\] \[**-N** *system*\] \[**-s** *signal*\] *file ...*

## DESCRIPTION

The **fuser** utility writes to standard output the process IDs of processes running on the local system that have one or more of the named files open. If *file* is a mounted block device, the output will show all processes having files opened on that file system.

The options are as follows:

- **-c**

  The file is treated as a mount point and **fuser** will report on any files open in the file system.

- **-f**

  Report only for the named file(s).

- **-k**

  Send the SIGKILL signal to each process.

- **-M** *core*

  Extract values associated with the name list from the specified core instead of the running kernel.

- **-N** *system*

  Extract the name list from the specified system instead of the running kernel.

- **-s** *signal*

  Send the specified *signal* to each process. The *signal* may be specified as a signal number or as a symbolic name either with or without the “SIG” prefix. Signal names are not case sensitive. For example, the following signal arguments are equivalent: “9”, “kill”, “SIGKILL”.

- **-u**

  The username of the process using the file will be printed in brackets to standard error. If the username is unable to be determined, the real user ID will be printed instead.

The **-c** and **-f** options are mutually exclusive.

The name of the file followed by a colon (‘:’) is printed to standard error. The following characters may be printed to standard error after the process ID if the described conditions are true:

- c

  The file is the process's current working directory.

- r

  The file is the process's root directory.

- t

  The file is the process's executable text.

## EXIT STATUS

The **fuser** utility exits 0 on success, and \>0 if an error occurs.

## EXAMPLES

Print the process IDs of any processes holding files open under the */mnt* filesystem:

```
$ fuser -c /mnt
```

Send SIGTERM to any process holding a file open under the */mnt* filesystem:

```
# fuser -c -s term /mnt
```

Report on all files opened under the filesystem on which */dev/wd0a* is mounted:

```
$ fuser /dev/wd0a
```

Report on all processes currently holding */dev/wd0a* open:

```
$ fuser -f /dev/wd0a
```

## SEE ALSO

[fstat(1)](/fstat/1.md), [kill(1)](/kill/1.md), [signal(3)](/signal/3.md), [mount(8)](/mount/8.md)

## STANDARDS

The **fuser** utility is compliant with the X/Open System Interfaces option of the IEEE Std 1003.1-2008 (“POSIX.1”) specification.

The flags \[**-kMNs**\] are extensions to that specification.

## HISTORY

The **fuser** utility has been available since OpenBSD 4.7.