Preface
Introduction
Practice Setup
Linux Architecture
Basic Commands
Basic file management or operations on file
User administration
Networking
Linux Interview Questions

 

 

Free command

This command is used to get the free space including used physical space, swapped memory in the system and buffer used by the kernel.

$ free [ options ]

# free total  used    free     shared       buffers      cached
Mem:        1021628  912548    109080           0         120368    
655548
-/+ buffers/cache:             136632       884996
Swap:       4194296    0       4194296

 

Options

  • -b: Displays the amount of the memory in bytes
# free -b 
total      used         free        shared     buffers  cached
Mem:       1046147072   934420480  111726592     0     123256832 
671281152
-/+ buffers/cache:      139882496  906264576  
Swap:      4294959104      0       4294959104

 

  • -k : Displays the amount of the memory in kilobytes
# free -k 
total     used      free     shared    buffers  cached
Mem:     1021628   912520    109108      0      120368    
655548
-/+ buffers/cache: 136604    885024
Swap:    4194296      0     4194296

 

  • -m: Displays the amount of the memory in megabytes
# free -m 
total  used        free    shared   buffers    cached
Mem:   997         891     106        0         117       
640
-/+ buffers/cache: 133     864
Swap:              4095     0       4095

 

  • -g: Displays the amount of the memory in gigabytes.
# free -g
total        used      free    shared  buffers  cached
Mem:           0        0       0        0         0
0
-/+ buffers/cache:      0       0
Swap:          3        0       3

 

  • -tera : Displays the amount of the memory in terabytes.

 

  • -h : Displays automatically the output fields with three digit numbers. Each digit will specify as follows

    • B : Bytes

    • K : KiloBytes

    • M: MegaBytes

    • G : GigaBytes

    • T : TeraBytes

 

  • -l : To display the detailed high and low memory size in statistical way.
# free -l 
total     used     free      shared     buffers  cache  
Mem:      1021628  912368    109260       0      120368    
655548
Low:      890036    789064   100972
High:     131592    123304   8288  
-/+ buffers/cache:  136452   885176
Swap:     4194296     0      4194296

 

  • -s : With a digit to update the command at particular intervals.
# free -s  5 
total     used       free       shared  buffers cached
Mem:      1021628   912368      109260    0     120368    
655548
-/+ buffers/cache:  136452      885176  
Swap:     4194296     0         4194296

 

  • -o, --old : Display the output in old format; the only difference being this option will disable the display of the "buffer adjusted" line.
# free -o
total     used       free     shared  buffers  cached
Mem:    1021628     912520    109108    0      120368    
655548
Swap:   4194296        0     4194296

 

  • -V : Gives the information about the version.
  # free -V
  procps version 3.2.8

 

  • -t : List out the total lines at the end of the command.
  # free -t 
total    used     free   shared  buffers  cached
Mem:   1021628   912520  109108    0       120368    
655548
-/+ buffers/cache:136604 885024  
Swap: 4194296     0      4194296
Total:5215924  912520    4303404