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Linux in a Nutshell

This directory of Linux commands is from Linux in a Nutshell, 5th Edition.

Click on any of the 687 commands below to get a description and list of available options. All links in the command summaries point to the online version of the book on Safari Bookshelf.

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ipcs [options]

System administration command. Print report on interprocess communication (IPC) message queues, shared memory segments, and semaphore arrays for which the current process has read access. Options can be used to specify the type of resources to report on and the output format of the report.


Resource specification options:


Report on all IPC facilities: shared memory segments, message queues, and semaphore arrays. This is the default.


Report on shared memory segments.


Report on message queues.


Report on semaphore arrays.

Output format options:


Print information on maximum size of the resource: size in bytes of messages or shared memory segments, and the number of semaphores per set in the case of semaphore arrays.


Print creator and owner user IDs for IPC facilities.


Print resource maximum and minimum limits.


Print outstanding usage of the resource in question: the number of messages and the total size of the message queue, or the number of processes using shared memory segments.


Print creator and last operation process identifiers.


Print attach, detach, and change times for shared memory segments, last operation and change times for semaphore arrays, and send, receive, and change times for message queues.


Print summary of current resource usage.

Other options:


Print help message, then exit.

-i identifier

Used in combination with the -m, -q, or -s options. Report only on the resource specified by numeric identifier.

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