---
name: "proc_locks"
section: "5"
platform: "linux"
package: "man-pages"
version: "6.19-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/proc_locks"
---

# proc\_locks(5)

current file locks and leases

## NAME

/proc/locks - current file locks and leases

## DESCRIPTION

- */proc/locks*

  This file shows current file locks ([**flock**(2)](/flock/2.md) and [**fcntl**(2)](/fcntl/2.md)) and leases ([**fcntl**(2)](/fcntl/2.md)).

-

  An example of the content shown in this file is the following:

-

  ```
  1: POSIX  ADVISORY  READ  5433 08:01:7864448 128 128
  2: FLOCK  ADVISORY  WRITE 2001 08:01:7864554 0 EOF
  3: FLOCK  ADVISORY  WRITE 1568 00:2f:32388 0 EOF
  4: POSIX  ADVISORY  WRITE 699 00:16:28457 0 EOF
  5: POSIX  ADVISORY  WRITE 764 00:16:21448 0 0
  6: POSIX  ADVISORY  READ  3548 08:01:7867240 1 1
  7: POSIX  ADVISORY  READ  3548 08:01:7865567 1826 2335
  8: OFDLCK ADVISORY  WRITE -1 08:01:8713209 128 191
  ```

-

  The fields shown in each line are as follows:

  - \[1\]

    The ordinal position of the lock in the list.

  - \[2\]

    The lock type. Values that may appear here include:

    - **FLOCK**

      This is a BSD file lock created using [**flock**(2)](/flock/2.md).

    - **OFDLCK**

      This is an open file description (OFD) lock created using [**fcntl**(2)](/fcntl/2.md).

    - **POSIX**

      This is a POSIX byte-range lock created using [**fcntl**(2)](/fcntl/2.md).

  - \[3\]

    Among the strings that can appear here are the following:

    - **ADVISORY**

      This is an advisory lock.

    - **MANDATORY**

      This is a mandatory lock.

  - \[4\]

    The type of lock. Values that can appear here are:

    - **READ**

      This is a POSIX or OFD read lock, or a BSD shared lock.

    - **WRITE**

      This is a POSIX or OFD write lock, or a BSD exclusive lock.

  - \[5\]

    The PID of the process that owns the lock.

  -

    Because OFD locks are not owned by a single process (since multiple processes may have file descriptors that refer to the same open file description), the value -1 is displayed in this field for OFD locks. (Before Linux 4.14, a bug meant that the PID of the process that initially acquired the lock was displayed instead of the value -1.)

  - \[6\]

    Three colon-separated subfields that identify the major and minor device ID of the device containing the filesystem where the locked file resides, followed by the inode number of the locked file.

  - \[7\]

    The byte offset of the first byte of the lock. For BSD locks, this value is always 0.

  - \[8\]

    The byte offset of the last byte of the lock. **EOF** in this field means that the lock extends to the end of the file. For BSD locks, the value shown is always *EOF*.

-

  Since Linux 4.9, the list of locks shown in */proc/locks* is filtered to show just the locks for the processes in the PID namespace (see [**pid\_namespaces**(7)](/pid_namespaces/7.md)) for which the */proc* filesystem was mounted. (In the initial PID namespace, there is no filtering of the records shown in this file.)

-

  The [**lslocks**(8)](/lslocks/8.md) command provides a bit more information about each lock.

## SEE ALSO

[**proc**(5)](/proc/5.md)