Sysinfo

sysinfo

Cross-platform library for retrieving system information: processes, CPUs, memory, disks, and networks.

Key Types

Core Types

Refresh Kind Types (Performance Critical)

Usage in script-kit-gpui

Process Manager (process_manager.rs)

The crate is used for orphan process detection - checking if child bun processes are still running:

use sysinfo::{Pid, System};

/// Check if a process is currently running
pub fn is_process_running(&self, pid: u32) -> bool {
    let mut system = System::new();
    system.refresh_processes(sysinfo::ProcessesToUpdate::All, true);
    system.process(Pid::from_u32(pid)).is_some()
}

Key patterns used:

• System::new() - Create minimal system instance
• refresh_processes(ProcessesToUpdate::All, true) - Refresh all processes, remove dead ones
• system.process(Pid::from_u32(pid)) - Look up specific process by PID
• Pid::from_u32() - Convert platform u32 to sysinfo's Pid type

Process Information

Checking if Process Exists

use sysinfo::{Pid, ProcessesToUpdate, System};

let mut sys = System::new();
sys.refresh_processes(ProcessesToUpdate::All, true);

// Check by PID
if let Some(process) = sys.process(Pid::from_u32(1234)) {
    println!("Process {} is running", process.name().to_string_lossy());
}

// Check specific PIDs only (more efficient)
let pids = [Pid::from_u32(1234), Pid::from_u32(5678)];
sys.refresh_processes(ProcessesToUpdate::Some(&pids), true);

Process Properties

// Available on Process
process.pid()           // -> Pid
process.name()          // -> &OsStr (limited to 15 chars on Linux!)
process.exe()           // -> Option<&Path>
process.cmd()           // -> &[OsString]
process.cwd()           // -> Option<&Path>
process.environ()       // -> &[OsString]
process.memory()        // -> u64 (RSS in bytes)
process.virtual_memory() // -> u64
process.cpu_usage()     // -> f32 (percentage)
process.status()        // -> ProcessStatus
process.parent()        // -> Option<Pid>
process.start_time()    // -> u64 (Unix timestamp)
process.run_time()      // -> u64 (seconds)

Killing Processes

use sysinfo::Signal;

// Simple kill (SIGKILL)
process.kill();

// Kill with specific signal
if let Some(success) = process.kill_with(Signal::Term) {
    println!("Signal sent: {}", success);
}

// Wait for termination
process.wait();

Refresh Patterns

CRITICAL: Always Refresh Before Reading

sysinfo works on diffs - you must refresh to get current data:

// BAD - stale data
let sys = System::new_all();
let mem = sys.used_memory(); // May be outdated!

// GOOD - fresh data  
let mut sys = System::new();
sys.refresh_memory();
let mem = sys.used_memory();

Performance: Refresh Only What You Need

use sysinfo::{ProcessRefreshKind, ProcessesToUpdate, System};

// SLOW - refreshes everything
sys.refresh_all();

// FAST - only refresh processes, only memory info
sys.refresh_processes_specifics(
    ProcessesToUpdate::All,
    true, // remove dead processes
    ProcessRefreshKind::nothing().with_memory(),
);

// FASTEST - check specific PIDs only
let pids = [Pid::from_u32(1234)];
sys.refresh_processes(ProcessesToUpdate::Some(&pids), true);

ProcessRefreshKind Builder

use sysinfo::{ProcessRefreshKind, UpdateKind};

// Nothing (fastest)
ProcessRefreshKind::nothing()

// Everything (slowest)
ProcessRefreshKind::everything()

// Custom - only what you need
ProcessRefreshKind::nothing()
    .with_memory()      // RSS, virtual memory
    .with_cpu()         // CPU usage
    .with_disk_usage()  // Disk I/O
    .with_exe(UpdateKind::OnlyIfNotSet) // Executable path

Reuse System Instance

// BAD - creates new instance each time
fn check_process(pid: u32) -> bool {
    let mut sys = System::new();
    sys.refresh_processes(ProcessesToUpdate::All, true);
    sys.process(Pid::from_u32(pid)).is_some()
}

// GOOD - reuse instance (especially for CPU usage which needs history)
struct ProcessMonitor {
    sys: System,
}

impl ProcessMonitor {
    fn check_process(&mut self, pid: u32) -> bool {
        self.sys.refresh_processes(ProcessesToUpdate::All, true);
        self.sys.process(Pid::from_u32(pid)).is_some()
    }
}

CPU Usage Notes

CPU usage requires two measurements with time between them:

use sysinfo::{System, MINIMUM_CPU_UPDATE_INTERVAL};
use std::thread;

let mut sys = System::new_all();

// First measurement (will be 0%)
sys.refresh_cpu_usage();

// Wait minimum interval
thread::sleep(MINIMUM_CPU_UPDATE_INTERVAL);

// Second measurement (accurate)
sys.refresh_cpu_usage();

for cpu in sys.cpus() {
    println!("{}%", cpu.cpu_usage());
}

Platform Differences

Process Names on Linux

• Limited to 15 characters
• May not match executable name
• Use process.exe() for full path when available

macOS Sandboxing

For App Store apps, use feature flags:

[dependencies]
sysinfo = { version = "0.33", features = ["apple-app-store"] }

Windows

• Admin privileges may be needed for some process info
• PID is usize, not pid_t

Pid Conversions

use sysinfo::Pid;

// From u32 (most portable)
let pid = Pid::from_u32(1234);

// To u32
let n: u32 = pid.as_u32();

// From/to usize (platform-specific)
let pid = Pid::from(1234_usize);
let n: usize = pid.into();

// Parse from string
let pid: Pid = "1234".parse().unwrap();

Anti-patterns

Creating System::new_all() Repeatedly

// BAD - expensive allocation every call
fn get_memory() -> u64 {
    System::new_all().used_memory()
}

// GOOD - reuse instance
fn get_memory(sys: &mut System) -> u64 {
    sys.refresh_memory();
    sys.used_memory()
}

Not Refreshing Before Reading

// BAD - returns initialization values (often 0)
let sys = System::new();
let procs = sys.processes(); // Empty!

// GOOD
let mut sys = System::new();
sys.refresh_processes(ProcessesToUpdate::All, true);
let procs = sys.processes();

Refreshing Everything When You Need One Thing

// BAD - refreshes CPUs, memory, processes, etc.
sys.refresh_all();
let mem = sys.used_memory();

// GOOD - only refresh memory
sys.refresh_memory();
let mem = sys.used_memory();

Trusting process.name() on Linux

// BAD - may be truncated or changed
let name = process.name(); // "my-very-long-a" (truncated!)

// GOOD - use exe when available
let name = process.exe()
    .and_then(|p| p.file_name())
    .map(|n| n.to_string_lossy().to_string())
    .unwrap_or_else(|| process.name().to_string_lossy().to_string());

Reading CPU Usage Without History

// BAD - first reading is always 0%
let mut sys = System::new_all();
let cpu = sys.global_cpu_usage(); // 0%!

// GOOD - wait for second sample
let mut sys = System::new_all();
std::thread::sleep(sysinfo::MINIMUM_CPU_UPDATE_INTERVAL);
sys.refresh_cpu_usage();
let cpu = sys.global_cpu_usage(); // Accurate!

Common Patterns

Find Process by Name

// Exact name match
for process in sys.processes_by_exact_name("bun".as_ref()) {
    println!("{}: {}", process.pid(), process.name().to_string_lossy());
}

// Substring match  
for process in sys.processes_by_name("bun".as_ref()) {
    println!("{}: {}", process.pid(), process.name().to_string_lossy());
}

Monitor Process Until Exit

use std::time::Duration;

fn wait_for_exit(pid: u32, timeout: Duration) -> bool {
    let mut sys = System::new();
    let deadline = std::time::Instant::now() + timeout;
    let target_pid = Pid::from_u32(pid);
    
    while std::time::Instant::now() < deadline {
        sys.refresh_processes(
            ProcessesToUpdate::Some(&[target_pid]),
            true
        );
        if sys.process(target_pid).is_none() {
            return true; // Process exited
        }
        std::thread::sleep(Duration::from_millis(100));
    }
    false // Timeout
}

Feature Flags

[dependencies]
sysinfo = { version = "0.33", default-features = false }

# Optional features:
# - multithread: Parallel refresh (increases memory on macOS)
# - serde: Serialize System and related types
# - apple-app-store: Disable APIs prohibited in App Store
# - apple-sandbox: Sandbox-safe subset

References

• docs.rs/sysinfo
• GitHub: GuillaumeGomez/sysinfo
• Migration Guide