How to discover number of logical cores on Mac OS X

Question

How can you tell  from the command line  how many cores are on the machine when you re running Mac OS X   On Linux  I use   x   awk    processor     n  END  print n 1    proc cpuinfo    It s not perfect  but it s close   This is intended to get fed to make  which is why it gives a result 1 higher than the actual number   And I know the above code can be written denser in Perl or can be written using grep  wc  and cut  but I decided the above was a good tradeoff between conciseness and readability   VERY LATE EDIT  Just to clarify  I m asking how many logical cores are available  because this corresponds with how many simultaneous jobs I want make to spawn  jkp s answer  further refined by Chris Lloyd  was exactly what I needed  YMMV

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This should be cross platform  At least for Linux and Mac OS X   python -c  import multiprocessing as mp  print mp cpu count       A little bit slow but works

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Comments for 2 good replies above   1  re the accepted reply  and comments  by jkp   hw ncpu is apparently deprecated in favor of hw logicalcpu  https   ghc haskell org trac ghc ticket 8594   2  re the 2014 update by Karl Ehr   on my computer  with 2 5 ghz intel core i7  sysctl -a   grep machdep cpu   grep per package returns different numbers   machdep cpu logical per package  16  machdep cpu cores per package  8  The desired values are   machdep cpu core count  4  machdep cpu thread count  8  Which match   hw physicalcpu  4  hw logicalcpu  8

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CLARIFICATION  When this question was asked the OP did not say that he wanted the number of LOGICAL cores rather than the actual number of cores  so this answer logically  no pun intended  answers with a way to get the actual number of real physical cores  not the number that the OS tries to virtualize through hyperthreading voodoo   UPDATE TO HANDLE FLAW IN YOSEMITE  Due to a weird bug in OS X Yosemite  and possibly newer versions  such as the upcoming El Capitan   I ve made a small modification   The old version still worked perfectly well if you just ignore STDERR  which is all the modification does for you      Every other answer given here either    gives incorrect information gives no information  due to an error in the command implementation runs unbelievably slowly  taking the better part of a minute to complete   or gives too much data  and thus might be useful for interactive use  but is useless if you want to use the data programmatically  for instance  as input to a command like bundle install --jobs 3 where you want the number in place of 3 to be one less than the number of cores you ve got  or at least not more than the number of cores    The way to get just the number of cores  reliably  correctly  reasonably quickly  and without extra information or even extra characters around the answer  is this   system profiler SPHardwareDataType 2 gt   dev null   grep  Total Number of Cores    cut -d  -f2   tr -d

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The following command gives you all information about your CPU    sysctl -a   sort   grep cpu

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getconf works both in Mac OS X and Linux  just in case you need it to be compatible with both systems    getconf  NPROCESSORS ONLN 12

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To do this in C you can use the sysctl 3  family of functions   int count  size t count len   sizeof count   sysctlbyname  hw logicalcpu    amp count   amp count len  NULL  0   fprintf stderr  you have  i cpu cores   count     Interesting values to use in place of  hw logicalcpu   which counts cores  are   hw physicalcpu - The number of physical processors available in the current power management mode   hw physicalcpu max - The maximum number of physical processors that could be available this boot   hw logicalcpu - The number of logical processors available in the current power management mode   hw logicalcpu max - The maximum number of logical processors that could be available this boot

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On a MacBook Pro running Mavericks  sysctl -a   grep hw cpu will only return some cryptic details   Much more detailed and accessible information is revealed in the machdep cpu section  ie   sysctl -a   grep machdep cpu   In particular  for processors with HyperThreading  HT   you ll see the total enumerated CPU count  logical per package  as double that of the physical core count  cores per package      sysctl -a   grep machdep cpu    grep per package

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As jkp said in a comment  that doesn t show the actual number of physical cores  to get the number of physical cores you can use the following command   system profiler SPHardwareDataType

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You can do this using the sysctl utility   sysctl -n hw ncpu

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Even easier   sysctl -n hw ncpu

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This can be done in a more portable way     nproc --all 32   Compatible with macOS and Linux

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system profiler SPHardwareDataType shows I have 1 processor and 4 cores       system profiler SPHardwareDataType Hardware       Hardware Overview         Model Name  MacBook Pro       Model Identifier  MacBookPro9 1       Processor Name  Intel Core i7       Processor Speed  2 6 GHz       Number of Processors  1       Total Number of Cores  4         lt snip gt          However  sysctl disagrees       sysctl -n hw logicalcpu 8     sysctl -n hw physicalcpu 4        But sysctl appears correct  as when I run a program that should take up all CPU slots  I see this program taking close to 800  of CPU time  in top    PID   COMMAND       CPU   4306  top          5 6    4304  java         745 7  4296  locationd    0 0

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system profiler   grep  Total Number Of Cores

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It wasn t specified in the original question  although I saw OP post in comments that this wasn t an option   but many developers on macOS have the Homebrew package manager installed   For future developers who stumble upon this question  as long as the assumption  or requirement  of Homebrew being installed exists  e g   in an engineering organization in a company   nproc is one of the common GNU binaries that is included in the coreutils package   brew install coreutils   If you have scripts that you would prefer to write once  for Linux   macOS  instead of twice  or to avoid having if blocks where you need to detect the OS to know whether or not to call nproc vs sysctl -n hw logicalcpu  this may be a better option

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Use the system profiler   grep  quot Cores quot  command  I have a   MacBook Pro Retina  Mid 2012  Processor  2 6 GHz Intel Core i7  user  system profiler   grep  quot Cores quot        Total Number of Cores  4   user  sysctl -n hw ncpu 8  According to Wikipedia   http   en wikipedia org wiki Intel Core Core i7  there is no Core i7 with 8 physical cores so the Hyperthreading idea must be the case   Ignore sysctl and use the system profiler value for accuracy   The real question is whether or not you can efficiently run applications with 4 cores  long compile jobs   without interrupting other processes  Running a compiler parallelized with 4 cores doesn t appear to dramatically affect regular OS operations   So perhaps treating it as 8 cores is not so bad

[macos] How to discover number of logical cores on Mac OS X?

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