- Unix Commands Reference
- Unix - Tutorial Home
- Selected Reading
- UPSC IAS Exams Notes
- Developer's Best Practices
- Questions and Answers
- Effective Resume Writing
- HR Interview Questions
- Computer Glossary
- Who is Who
ipcrm - Unix, Linux Command
NAMEipcrm - remove a message queue, semaphore set or shared memory id
SYNOPSISipcrm [ -M key | -m id | -Q key | -q id | -S key | -s id ] ...
ipcrm [ shm | msg | sem ] id ...
DESCRIPTIONipcrm 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).
|removes the shared memory segment created with shmkey after the last detach is performed.|
|removes the shared memory segment identified by shmid after the last detach is performed.|
|removes the message queue created with msgkey.|
|removes the message queue identified by msgid.|
|removes the semaphore created with semkey.|
|removes the semaphore identified by semid.|
NOTESIn 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.