How to check virtual memory in linux

ipcs shows information on the inter-process communication facilities for which the calling process has read access. By default, it shows information about all three resources: shared memory segments, message queues, and semaphore arrays.
Without options, the information shall be written in short format for message queues, shared memory segments, and semaphore sets that are currently active in the system.

Otherwise, the information that is displayed is controlled by the options specified.

Options :

• -q : Write information about active message queues.
• -m : Write information about active shared memory segments.
• -s : Write information about active semaphore sets.
• -a : Use all print options.

  (This is a shorthand notation for -b, -c, -o, -p, and -t.)

• -b : Write information on maximum allowable size. (Maximum number of bytes in messages on queue for message queues, size of segments for shared memory, and number of semaphores in each set for semaphores.)
• -c : Write creator’s user name and group name;.
• -o : Writ
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