Read system information

std.system reads Linux’s /proc files into typed values. Open the source once, then ask for the information needed. Each query is fresh and fallible:

import std.system
from std.system import SystemError

def main() -> Result[(), IoError | SystemError]:
    source = std.system.local()?
    cpus = source.cpu_count()?
    memory = source.memory()?
    uptime = source.uptime()?
    print("CPU information available:", cpus > 0)?
    print("Memory information available:", memory.total_bytes > 0u64)?
    print("Uptime available:", uptime.seconds >= 0.0)?
    Ok(())

CPU information available: True
Memory information available: True
Uptime available: True

The example prints checks so its output stays the same on different machines. A monitor can print cpus, memory.total_bytes and uptime.seconds directly. There is no timer or background thread: another call reads another snapshot.

For memory headroom, prefer available_bytes to free_bytes: the kernel’s available estimate includes memory it expects to reclaim. The field is optional because not every source provides it. Here is how to keep absence distinct from zero, using sample values so both paths are visible:

import std.system

def show_available(memory: &std.system.Memory) -> Result[(), IoError]:
    match memory.available_bytes:
        case Some(bytes):
            print("available bytes:", bytes)?
        case Nothing:
            print("available memory is not reported")?
    Ok(())

def main() -> Result[(), IoError]:
    reported = std.system.Memory(8192u64, 1024u64, Some(4096u64), 0u64, 0u64)
    absent = std.system.Memory(8192u64, 1024u64, Nothing, 0u64, 0u64)
    show_available(&reported)?
    show_available(&absent)?
    Ok(())

available bytes: 4096
available memory is not reported

Reads have default byte limits; override them with a named argument such as source.memory(max_bytes=65536). A file that exceeds the limit produces an error, not a truncated record. open_procfs(&path) reads a different procfs mount or captured directory, useful when testing a monitoring tool.

process_ids() returns a bounded, sorted list of visible process IDs. process(pid) reads one status record. Processes can exit between those calls, and access can be denied; handle the SystemError.Io cause rather than treating the whole list as guaranteed live. Use std.process to manage children your program starts.

block_devices() reports device and partition sizes; disk_io() reports counters. Avoid summing whole disks with their partitions. Neither gives free filesystem space. CPU and memory values can describe the host even inside a container; they are not cgroup quota measurements or a recommendation for how many workers to start.

See std.system for fields, units, error variants and snapshot limitations.