ipcrm — remove a message queue, semaphore set or shared memory id


ipcrm [options]

ipcrm shm | msg | sem id...


ipcrm removes System V interprocess 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 '0x' or '0X'), or octal (specified with an initial '0').


−M, −−shmem−key shmkey

removes the shared memorysegment created with shmkey after the last detach is performed.

−m, −−shmem−id shmid

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

−Q, −−queue−key msgkey

removes the message queue created with msgkey.

−q, −−queue−id msgid

removes the message queue identified by msgid.

−S, −−semaphore−key semkey

removes the semaphore created with semkey.

−s, −−semaphore−id semid

removes the semaphore identified by semid.

−a, −−all [shm msg sem]

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

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


In its first Linux implementation, ipcrm used the deprecated syntax shown in 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.


ipcs(1), ipcmk(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