How to obtain the number of CPUs cores in Linux from the command line

Question

I have this script  but I do not know how to get the last element in the printout   cat  proc cpuinfo   awk    processor  print  3     The last element should be the number of CPUs  minus 1

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You can also use Python  To get the number of physical cores     python -c  import psutil  print psutil cpu count logical False    4   To get the number of hyperthreaded cores     python -c  import psutil  print psutil cpu count logical True    8

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Not my web page  but this command from http   www ixbrian com blog  p 64 amp cm mc uid 89402252817914508279022 amp cm mc sid 50200000 1450827902 works nicely for me on centos  It will show actual cpus even when hyperthreading is enabled   cat  proc cpuinfo   egrep  core id physical id    tr -d   n    sed s physical   nphysical g   grep -v      sort   uniq   wc -l

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Processing the contents of  proc cpuinfo is needlessly baroque  Use nproc which is part of coreutils  so it should be available on most Linux installs   Command nproc prints the number of processing units available to the current process  which may be less than the number of online processors   To find the number of all installed cores processors use nproc --all  On my 8-core machine     nproc --all 8

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Count  core id  per  physical id  method using awk with fall-back on  processor  count if  core id  are not available  like raspberry   echo   awk    if   0   physical id     p  NF    if   0   core id     cores p NF  p NF    if   0  processor     cpu       END   for  key in cores    n       END   if  n   print n  else  print cpu      proc cpuinfo

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If you want to do this so it works on linux and OS X  you can do   CORES   grep -c  processor  proc cpuinfo 2 gt  dev null    sysctl -n hw ncpu

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Summary  to get physical CPUs do this   grep  core id   proc cpuinfo   sort -u   to get physical and logical CPUs do this   grep -c  processor  proc cpuinfo    proc  lt  lt  this is the golden source of any info you need about processes and    proc cpuinfo  lt  lt  is the golden source of any CPU information

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Use below query to get core details   oracle orahost  TESTDB   grep -c  processor  proc cpuinfo 8

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For the total number of physical cores   grep   core id   proc cpuinfo  sort -u wc -l   On multiple-socket machines  or always   multiply the above result by the number of sockets   echo      grep   physical id   proc cpuinfo   awk   print  4     sort -un   tail -1  1      mklement0 has quite a nice answer below using lscpu  I have written a more succinct version in the comments

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grep -c  processor  proc cpuinfo        will count the number of lines starting with  processor  in  proc cpuinfo  For systems with hyper-threading  you can use  grep  cpu  scores  proc cpuinfo   uniq    awk   print  4      which should return  for example  8  whereas the command above would return 16

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The above answers are applicable to most situations  but if you are in a docker container environment and your container is limited by CpusetCpus  then you can t actually get the real cpu cores through the above method  In this case  you need do this to get the real cpu cores  cat  proc stat   grep cpu   grep -E  cpu 0-9      wc -l

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lscpu gathers CPU architecture information form  proc cpuinfon in human-read-able format     lscpu   Architecture           x86 64 CPU op-mode s          32-bit  64-bit Byte Order             Little Endian CPU s                  8 On-line CPU s  list    0-7 Thread s  per core     1 Core s  per socket     4 CPU socket s           2 NUMA node s            1 Vendor ID              GenuineIntel CPU family             6 Model                  15 Stepping               7 CPU MHz                1866 669 BogoMIPS               3732 83 Virtualization         VT-x L1d cache              32K L1i cache              32K L2 cache               4096K NUMA node0 CPU s       0-7   See also https   unix stackexchange com questions 468766 understanding-output-of-lscpu

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You can use one of the following methods to determine the number of physical CPU cores    Count the number of unique core ids  roughly equivalent to grep -P   core id t   proc cpuinfo   sort -u   wc -l    awk    core id t   cores  NF     END  print length cores     proc cpuinfo Multiply the number of  cores per socket  by the number of sockets   lscpu   awk    Core  s   per socket    cores  NF     Socket  s      sockets  NF   END print cores sockets   Count the number of unique logical CPU s as used by the Linux kernel  The -p option generates output for easy parsing and is compatible with earlier versions of lscpu   lscpu -p   awk -F    0          cores  1     END  print length cores        Just to reiterate what others have said  there are a number of related properties   To determine the number of processors available   getconf  NPROCESSORS ONLN grep -cP   processor t   proc cpuinfo   To determine the number of processing units available  not necessarily the same as the number of cores   This is hyperthreading-aware   nproc   I don t want to go too far down the rabbit-hole  but you can also determine the number of configured processors  as opposed to simply available online processors  via getconf  NPROCESSORS CONF  To determine total number of CPU s  offline and online  you d want to parse the output of lscpu -ap

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Using getconf is indeed the most portable way  however the variable has different names in BSD and Linux to getconf  so you have to test both  as this gist suggests  https   gist github com jj1bdx 5746298  also includes a Solaris fix using ksh   I personally use     getconf  NPROCESSORS ONLN 2 gt  dev null    getconf NPROCESSORS ONLN 2 gt  dev null    echo 1   And if you want this in python you can just use the syscall getconf uses by importing the os module     python -c  import os  print os sysconf os sysconf names  SC NPROCESSORS ONLN        As for nproc  it s part of GNU Coreutils  so not available in BSD by default  It uses sysconf   as well after some other methods

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cat  proc cpuinfo   grep processor   This worked fine   When I tried the first answer I got 3 CPU s as the output   I know that I have 4 CPUs on the system so I just did a grep for processor and the output looked like this      root theservername     cat  proc cpuinfo   grep processor processor         0 processor         1 processor         2 processor         3

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If it s okay that you can use Python  then numexpr module has a function for this   In  5   import numexpr as ne  In  6   ne detect number of cores   Out 6   8   also this   In  7   ne ncores Out 7   8     To query this information from the command prompt use     runs whatever valid Python code given as a string with  -c  option   python -c  import numexpr as ne  print ne ncores   8     Or simply it is possible to get this info from multiprocessing cpu count   function    python -c  import multiprocessing  print multiprocessing cpu count       Or even more simply use os cpu count      python -c  import os  print os cpu count

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It is very simple  Just use this command   lscpu

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Here s the way I use for counting the number of physical cores that are online on Linux   lscpu --online --parse Core Socket   grep --invert-match        sort --unique   wc --lines   or in short   lscpu -b -p Core Socket   grep -v        sort -u   wc -l   Example  1 socket     gt  lscpu     CPU s                  28 Thread s  per core     2 Core s  per socket     14 Socket s               1       gt  lscpu -b -p Core Socket   grep -v        sort -u   wc -l 14   Example  2 sockets     gt  lscpu     CPU s                  56 Thread s  per core     2 Core s  per socket     14 Socket s               2      gt  lscpu -b -p Core Socket   grep -v        sort -u   wc -l 28   Example  4 sockets     gt  lscpu     CPU s                  64 Thread s  per core     2 Core s  per socket     8 Socket s               4      gt  lscpu -b -p Core Socket   grep -v        sort -u   wc -l 32

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This worked for me  tail -nX allows you to grab only the last X lines   cat  proc cpuinfo   awk    processor  print  3     tail -1   If you have hyperthreading  this should work for grabbing the number of physical cores   grep   core id   proc cpuinfo   sort -u   wc -l

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Preface     The problem with the  proc cpuinfo-based answers is that they parse information that was meant for human consumption and thus lacks a stable format designed for machine parsing  the output format can differ across platforms and runtime conditions  using lscpu -p on Linux  and sysctl on macOS  bypasses that problem  getconf  NPROCESSORS ONLN   getconf NPROCESSORS ONLN doesn t distinguish between logical and physical CPUs      Here s a sh  POSIX-compliant  snippet that works on Linux and macOS for determining the number of - online - logical or physical CPUs  see the comments for details   Uses lscpu for Linux  and sysctl for macOS   Terminology note  CPU refers to the smallest processing unit as seen by the OS  Non-hyper-threading cores each correspond to 1 CPU  whereas hyper-threading cores contain more  than 1  typically  2  - logical - CPU  Linux uses the following taxonomy 1   starting with the smallest unit  CPU  lt  core  lt  socket  lt  book  lt  node with each level comprising 1 or more instances of the next lower level      bin sh    macOS            Use  sysctl -n hw  cpu max   which returns the values of                     interest directly                     CAVEAT  Using the   max  key suffixes means that the  maximum                             available number of CPUs is reported  whereas the                            current power-management mode could make  fewer  CPUs                             available  dropping the   max  suffix would report the                            number of  currently  available ones  see  1  below      Linux            Parse output from  lscpu -p   where each output line represents                    a distinct  logical  CPU                     Note  Newer versions of  lscpu  support more flexible output                          formats  but we stick with the parseable legacy format                           generated by  -p  to support older distros  too                            -p  reports  online  CPUs only - i e   on hot-pluggable                           systems  currently disabled  offline  CPUs are NOT                          reported     Number of LOGICAL CPUs  includes those reported by hyper-threading cores      Linux  Simply count the number of  non-comment  output lines from  lscpu -p        which tells us the number of  logical  CPUs  logicalCpuCount       uname     Darwin     amp  amp                          sysctl -n hw logicalcpu max                            lscpu -p   egrep -v        wc -l     Number of PHYSICAL CPUs  cores       Linux  The 2nd column contains the core ID  with each core ID having 1 or            - in the case of hyperthreading - more logical CPUs             Counting the  unique  cores across lines tells us the            number of  physical  CPUs  cores   physicalCpuCount       uname     Darwin     amp  amp                          sysctl -n hw physicalcpu max                           lscpu -p   egrep -v        sort -u -t  -k 2 4   wc -l     Print the values  cat  lt  lt EOF   of logical CPUs    logicalCpuCount   of physical CPUS   physicalCpuCount EOF    1  macOS sysctl  3  documentation  Note that BSD-derived systems other than macOS - e g   FreeBSD - only support the hw ncpu key for sysctl  which are deprecated on macOS  I m unclear on which of the new keys hw npu corresponds to  hw  logical physical cpu  max    Tip of the hat to  teambob for helping to correct the physical-CPU-count lscpu command   Caveat  lscpu -p output does NOT include a  book  column  the man page mentions  books  as an entity between socket and node in the taxonomic hierarchy   If  books  are in play on a given Linux system  does anybody know when and how    the physical-CPU-count command may under-report  this is based on the assumption that lscpu reports IDs that are non-unique across higher-level entities  e g   2 different cores from 2 different sockets could have the same ID      If you save the code above as  say  shell script cpus  make it executable with chmod  x cpus and place it in folder in your  PATH  you ll see output such as the following     cpus logical  4 physical 4      1  Xaekai sheds light on what a book is   a book is a module that houses a circuit board with CPU sockets  RAM sockets  IO connections along the edge  and a hook for cooling system integration  They are used in IBM mainframes  Further info  http   ewh ieee org soc cpmt presentations cpmt0810a pdf

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Python 3 also provide a few simple ways to get it     python3 -c  import os  print os cpu count        4    python3 -c  import multiprocessing  print multiprocessing cpu count       4

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Quicker  without fork  This work with almsost all shell   ncore 0 while read line  do         line     amp  amp    -z    line processor       amp  amp  ncore    ncore 1     done  lt  proc cpuinfo echo  ncore 4   In order to stay compatible with shell  dash   busybox and others  I ve used ncore    ncore 1   instead of   ncore       bash version  ncore 0 while read -a line  do         line     processor     amp  amp    ncore       done  lt  proc cpuinfo echo  ncore 4

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The following should give you the number of  real  cores on both a hyperthreaded and non-hyperthreaded system  At least it worked in all my tests    awk -F     physical   amp  amp   ID  2    P    ID  2  1      cpu cores    CORES  2     END   print CORES P     proc cpuinfo

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dmidecode    grep -i cpu   grep Version  gives me  Version  Intel R  Xeon R  CPU E5-2667 v4   3 20GHz Version  Intel R  Xeon R  CPU E5-2667 v4   3 20GHz  Which is correct socket count - looking up the E5-2667 tells me each socket has 8 cores  so multiply and end up with 16 cores across 2 sockets  Where lscpu give me 20 CPUs - which is totally incorrect - not sure why   same goes for cat  proc cpu - ends up with 20

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Fravadona s answer is awesome and correct  but it requires the presence of lscpu  Since it is not present on the system where I need the number of physical cores  I tried to come up with one that relies only on proc cpuinfo cat  proc cpuinfo   grep -B2  core id    sed  s siblings        tr -d    space      sed  s --  n  g   sort -u   wc -l It works perfectly  but unfortunately it isn t as robust as Fravadona s  since it will break if  the name or order of the fields inside  proc cpuinfo changes grep replaces the line separator it inserts  currently --  by some other string   BUT  other than that  it works flawlessly    Here is a quick explanation of everything that is happening grep -B2  core id   get only the lines we are interested  i e  quot core id quot  and the 2 preceding lines  sed  s siblings       remove the  quot siblings    quot  line tr -d    space     replace spacing chars sed  s --  n  g  replace the  --  char  which was inserted by grep  by a line break sort -u  group by  quot physical id core id quot  wc -l  count the number of lines Being a total noobie  I was very pleased with myself when this worked  I never thought I would be able to join the required lines together to group by  quot physical id quot  and  quot core id quot   It is kind of hacky  but works  If any guru knows a way to simplify this mess  please let me know

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If you just want to count physical cores  this command did it for me   lscpu -e   tail -n  2   tr -s       cut -d     -f 4   sort   uniq   wc -w   Pretty basic  but seems to count actual physical cores  ignoring the logical count

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The most portable solution I have found is the getconf command   getconf  NPROCESSORS ONLN   This works on both Linux and Mac OS X  Another benefit of this over some of the other approaches is that getconf has been around for a long time  Some of the older Linux machines I have to do development on don t have the nproc or lscpu commands available  but they have getconf   Editor s note  While the getconf utility is POSIX-mandated  the specific  NPROCESSORS ONLN and  NPROCESSORS CONF values are not   That said  as stated  they work on Linux platforms as well as on macOS  on FreeBSD PC-BSD  you must omit the leading

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I also thought cat  proc cpuinfo would give me the correct answer  however I recently saw that my ARM quad core Cortex A53 system only showed a single core  It seems that  proc cpuinfo only shows the active cores  whereas   cat  sys devices system cpu present  is a better measure of what s there   You can also  cat  sys devices system cpu online  to see which cores are online  and  cat  sys devices system cpu offline  to see which cores are offline   The online  offline  and present sysfs entries return the index of the CPUS  so a return value of 0 just means core 0  whereas a return value of 1-3 means cores 1 2  and 3   See https   www kernel org doc Documentation ABI testing sysfs-devices-system-cpu

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Crossplatform solution for Linux  MacOS  Windows   CORES   grep -c  processor  proc cpuinfo 2 gt  dev null    sysctl -n hw ncpu    echo   NUMBER OF PROCESSORS

[linux] How to obtain the number of CPUs/cores in Linux from the command line?

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