ipcs
Report Inter-Process Communication facilities status
TLDR
Show information about all the IPC
Show information about active shared [m]emory segments, message [q]ueues or [s]empahore sets
Show information on maximum allowable size in [b]ytes
Show [c]reator’s user name and group name for all IPC facilities
Show the [p]ID of the last operators for all IPC facilities
Show access [t]imes for all IPC facilities
Show [o]utstanding usage for active message queues, and shared memory segments
SYNOPSIS
ipcs [options]
PARAMETERS
-m
Reports information about shared memory segments.
-q
Reports information about message queues.
-s
Reports information about semaphore sets.
-a
Reports information about all three IPC facilities: shared memory, message queues, and semaphores. This is equivalent to specifying -m -q -s.
-b
Provides brief listing. Shows only the key, id, owner, and size of each IPC resource.
-c
Shows creator's login name and group name.
-p
Shows process id's.
For shared memory: process ID of last attach and detach.
For semaphores: process ID of last operation.
-t
Shows access times. Shows the time of the last attach and detach.
For semaphores: shows the time of last change.
-l
Shows maximum shared memory segment size, maximum number of message queue bytes, or maximum number of semaphore sets.
-u
Shows usage summary.
-i id
Shows the details of a specific shared memory segment, message queue, or semaphore set, specified by its id.
-h
Display help text and exit.
DESCRIPTION
The ipcs command is a powerful utility in Linux systems used to report the status of Inter-Process Communication (IPC) facilities. It provides information about shared memory segments, message queues, and semaphore sets currently active on the system. This command is invaluable for system administrators and developers who need to monitor and manage IPC resources, diagnose issues related to inter-process communication, and understand how different processes are interacting with each other. ipcs allows users to view details such as the IDs, owners, permissions, sizes, and number of attached processes for each IPC resource.
It provides insight into resource utilization and potential bottlenecks which might be hindering system performance. Understanding ipcs output is crucial for debugging concurrent programs and ensuring efficient resource management in multi-process environments. The command can be used with various flags to filter or display specific types of IPC resources.
CAVEATS
The user needs appropriate privileges (usually root) to view information about IPC objects owned by other users. The output format might vary slightly depending on the specific Linux distribution.
UNDERSTANDING IPC RESOURCES
Inter-Process Communication (IPC) mechanisms such as shared memory, message queues, and semaphores enable different processes to communicate and synchronize with each other. These resources are managed by the kernel, and ipcs allows you to see their status.
TROUBLESHOOTING
When applications fail due to IPC related errors, ipcs can provide valuable information. By examining the status of shared memory, message queues, and semaphores, developers can identify potential issues such as resource exhaustion, permission problems, or incorrect resource IDs.
HISTORY
The ipcs command has been a standard part of Unix-like operating systems for a long time, evolving alongside the development of System V IPC mechanisms. It was designed to provide a standardized way to inspect and manage these resources. Its initial implementation was likely tied to the introduction of System V IPC in early Unix versions.
SEE ALSO
ipcrm(1), shmget(2), msgget(2), semget(2)
