Linux Command - free

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free - Display amount of free and used memory in the system.

Syntax

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free [OPTIONS]

Options

Common Option Description
-b, –bytes show output in bytes
-k, –kibi show output in kibibytes
-m, –mebi show output in mebibytes
-g, –gibi show output in gibibytes
-h, –human show human-readable output
-l, –lohi show detailed low and high memory statistics
-t, –total show total for RAM + swap
-s N, –seconds N repeat printing every N seconds
-c N, –count N repeat printing N times, then exit
-w, –wide wide output

Examples

Show free and used memory

Show in Human readable output

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free -h

Sample output

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             total       used       free     shared    buffers     cached
Mem:          7.7G       5.1G       2.6G       654M       542M       2.1G
-/+ buffers/cache:       2.5G       5.2G
Swap:         2.0G         0B       2.0

Show output in mebibytes

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free -m

Sample output

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             total       used       free     shared    buffers     cached
Mem:          7881       5229       2652        663        542       2161
-/+ buffers/cache:       2525       5356
Swap:         2047          0       2047

Show free and used memory, refresh every 5sec

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free -m -s 5

Reference