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//! Example demonstrating how to read system-wide file descriptor limits.
//!
//! This example shows the difference between:
//! - System-wide limits from /proc/sys/fs/
//! - Per-process limits from getrlimit()
//!
//! Run with: cargo run --example sys_limits
#[cfg(any(target_os = "linux", target_os = "android"))]
fn main() {
use rlimit::{Resource, SysLimits};
println!("=== System-wide File Descriptor Limits ===\n");
// Read system-wide limits
match SysLimits::read() {
Ok(limits) => {
if let Some(file_max) = limits.file_max {
println!("System file-max: {}", file_max);
println!(" (Maximum number of file descriptors system-wide)");
}
if let Some(file_nr) = &limits.file_nr {
println!("\nCurrent file descriptor usage:");
println!(" Allocated: {}", file_nr.allocated);
println!(" Free: {}", file_nr.free);
println!(" Maximum: {}", file_nr.maximum);
let usage_percent = if file_nr.maximum > 0 {
(file_nr.allocated as f64 / file_nr.maximum as f64) * 100.0
} else {
0.0
};
println!(" Usage: {:.2}%", usage_percent);
}
if let Some(nr_open) = limits.nr_open {
println!("\nPer-process nr_open: {}", nr_open);
println!(" (Maximum NOFILE limit that can be set per-process)");
}
}
Err(e) => {
eprintln!("Failed to read system limits: {}", e);
return;
}
}
println!("\n=== Per-process NOFILE Limit ===\n");
// Compare with per-process NOFILE limit
match Resource::NOFILE.get() {
Ok((soft, hard)) => {
println!("NOFILE soft limit: {}", soft);
println!("NOFILE hard limit: {}", hard);
println!(" (Limits for this process only)");
}
Err(e) => {
eprintln!("Failed to get NOFILE limit: {}", e);
}
}
println!("\n=== Key Differences ===\n");
println!("• file-max: System-wide limit on total file descriptors");
println!("• nr_open: Maximum value for per-process NOFILE limit");
println!("• NOFILE: Actual limit for this specific process");
println!();
println!("Hierarchy: file-max >= sum(all process NOFILE) and NOFILE <= nr_open");
}
#[cfg(not(any(target_os = "linux", target_os = "android")))]
fn main() {
println!("This example only works on Linux and Android systems.");
println!("System-wide limits are not available on this platform.");
}
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