proccpuinfo

/proc/cpuinfo is a virtual file in the Linux procfs that exposes information about the system’s CPUs to user space. It is generated by the kernel and reflects the CPU topology and capabilities at the moment of access. Reading the file does not modify system state, and the contents can change with hot-swaps, power events, or virtualization.

The file is located at /proc/cpuinfo. It presents information in per-CPU blocks, each beginning with a line like processor : N and followed by multiple key-value pairs. Common fields include vendor_id, cpu family, model, model name, stepping, microcode, cpu MHz, cache size, and flags. Topology information such as physical id and core id helps describe how CPUs are arranged across sockets and cores. On systems with multiple architectures, the exact set of fields can vary: for example, ARM machines may show a Features field instead of Flags, and some fields may be absent on certain CPUs.

Usage examples are straightforward. You can read the file with cat /proc/cpuinfo to see detailed information for every logical CPU. To count the number of processors, you can use grep -c '^processor' /proc/cpuinfo. To extract a single-line summary of the CPU model, grep '^model name' /proc/cpuinfo | head -n 1. The lscpu command provides a formatted summary derived from /proc/cpuinfo and other kernel sources.

Limitations include that /proc/cpuinfo is a snapshot that may not reflect dynamic frequency changes or virtualization-induced restrictions. In containers, information may be restricted by the host or Linux namespaces, and fields vary by architecture and kernel version.

See also: procfs, lscpu, /proc.