$ Linux Command

System

nproc

Print the number of processing units available.

cpucoresthreadsprocessinghardware

Additional Notes

nproc prints the number of processing units available to the current process. This includes all online CPU cores and threads. It reads from sched_getaffinity and CPU information under /sys and /proc to determine availability.

It is commonly used in build scripts and parallel processing to determine how many jobs to run concurrently. For example, make -j$(nproc) tells make to run as many parallel jobs as there are CPU cores, maximizing build speed.

Syntax

nproc [options]

Parameters

  • options: Flags that change how nproc behaves.
  • target: Optional file, device, interface, user, service, or command target when the command supports one.

Common Options

  • --all: Print the total number of installed processors, including offline CPUs.
  • --ignore=N: Exclude N processing units from the count.
  • --help: Show help and exit.
  • --version: Show version information.

Examples

nproc

Print the number of processing units available.

make -j$(nproc)

Run make with as many parallel jobs as there are cores.

nproc --all

Show the total number of installed processors, including offline ones.

nproc --ignore=2

Return the number of available processing units minus 2.

echo $(($(nproc) / 2))

Half the available cores, useful for I/O-bound workloads.

Practical Notes

  • nproc respects CPU affinity. If the process is restricted to specific cores, nproc reports only those cores.
  • For containers and cgroups, nproc reports the limit set by the cgroup CPU quota.
  • Use lscpu or nproc --all to see the total hardware CPUs regardless of affinity or offline state.
  • In scripts, always quote $(nproc) properly: make -j "$(nproc)".
  • Older systems may not have nproc installed; it is part of GNU Coreutils since version 8.4.