Section (1) ipcrm

Linux manual pages Section 1  


ipcrm — remove certain IPC resources


ipcrm [options]

ipcrm shm | msg | sem id...


ipcrm removes System V inter-process communication (IPC) objects and associated data structures from the system. In order to delete such objects, you must be superuser, or the creator or owner of the object.

System V IPC objects are of three types: shared memory, message queues, and semaphores. Deletion of a message queue or semaphore object is immediate (regardless of whether any process still holds an IPC identifier for the object). A shared memory object is only removed after all currently attached processes have detached (shmdt(2)) the object from their virtual address space.

Two syntax styles are supported. The old Linux historical syntax specifies a three-letter keyword indicating which class of object is to be deleted, followed by one or more IPC identifiers for objects of this type.

The SUS-compliant syntax allows the specification of zero or more objects of all three types in a single command line, with objects specified either by key or by identifier (see below). Both keys and identifiers may be specified in decimal, hexadecimal (specified with an initial _zsingle_quotesz_0x_zsingle_quotesz_ or _zsingle_quotesz_0X_zsingle_quotesz_), or octal (specified with an initial _zsingle_quotesz_0_zsingle_quotesz_).

The details of the removes are described in shmctl(2), msgctl(2), and semctl(2). The identifiers and keys can be found by using ipcs(1).


−a, −−all [shm] [msg] [sem]

Remove all resources. When an option argument is provided, the removal is performed only for the specified resource types. Warning! Do not use −a if you are unsure how the software using the resources might react to missing objects. Some programs create these resources at startup and may not have any code to deal with an unexpected disappearance.

−M, −−shmem−key shmkey

Remove the shared memory segment created with shmkey after the last detach is performed.

−m, −−shmem−id shmid

Remove the shared memory segment identified by shmid after the last detach is performed.

−Q, −−queue−key msgkey

Remove the message queue created with msgkey.

−q, −−queue−id msgid

Remove the message queue identified by msgid.

−S, −−semaphore−key semkey

Remove the semaphore created with semkey.

−s, −−semaphore−id semid

Remove the semaphore identified by semid.

−V, −−version

Display version information and exit.

−h, −−help

Display help text and exit.


In its first Linux implementation, ipcrm used the deprecated syntax shown in the second line of the SYNOPSIS. Functionality present in other *nix implementations of ipcrm has since been added, namely the ability to delete resources by key (not just identifier), and to respect the same command-line syntax. For backward compatibility the previous syntax is still supported.


ipcmk(1), ipcs(1), msgctl(2), msgget(2), semctl(2), semget(2), shmctl(2), shmdt(2), shmget(2), ftok(3)


The ipcrm command is part of the util-linux package and is available from Linux Kernel Archive

  Copyright 2002 Andre C. Mazzone (
May be distributed under the GNU General Public License