function::jiffies - Linux

Overview

function::jiffies retrieves the current value of the Linux system timer, jiffies. This counter is incremented every system tick, providing a measure of elapsed time since system boot.

Syntax

ulong jiffies(void);

Options/Flags

None

Examples

Get the current system time in jiffies:

#include <linux/jiffies.h>

unsigned long current_time_jiffies = jiffies();

Calculate the time elapsed between two events in seconds:

#include <linux/jiffies.h>

unsigned long event1_jiffies = jiffies();
// ... Code to perform some operation
unsigned long event2_jiffies = jiffies();

double elapsed_seconds = (double)(event2_jiffies - event1_jiffies) / HZ;

Common Issues

  • Accuracy: The accuracy of jiffies is limited by the system tick rate, which is typically 100 ticks per second. This means that events occurring within the same system tick may have identical jiffies values.
  • Wrap-around: The jiffies counter is a 32-bit integer, which means it can wrap around after approximately 49 days of uptime. This can cause confusion when comparing time values across long periods of time.

Integration

jiffies can be integrated with other Linux commands to perform time-related operations:

  • rdate: Set the system clock using the current value of jiffies obtained from another host.
  • uptime: Display system uptime information, including the current value of jiffies.
  • Custom scripts: Utilize jiffies to create custom timekeeping and scheduling applications.

Related Commands

  • time: Measure execution time of commands.
  • getrusage: Get resource usage statistics for a process.
  • perf: Performance monitoring tool.