function::pstrace - Linux

Overview

pstrace is a powerful Linux command used to trace and debug processes by recording their system calls and other events. It can provide valuable insights into a process’s behavior, resource usage, and interactions with the system.

Syntax

pstrace [-a] [-e filter] [-g group] [-I interval] [-L length] [-M max] [-m min] [-o file] [-p pid | command] [-s sort] [-t] [-u user] [-V n] [-w] [-x events] [-z events]

Options/Flags

  • -a: Trace all processes.
  • -e filter: Filter events based on a specified expression (e.g., -e syscall:read).
  • -g group: Group events by specified criteria (e.g., -g pid).
  • -I interval: Set the sampling interval in microseconds (default: 0).
  • -L length: Specify the maximum length of the trace in bytes (default: 256 MB).
  • -M max: Set the maximum number of events to trace (default: unlimited).
  • -m min: Set the minimum number of events to trace (default: 0).
  • -o file: Save the trace to a specified file.
  • -p pid | command: Trace a specific process by PID or command name.
  • -s sort: Sort events by specified criteria (e.g., -s time).
  • -t: Trace the entire process tree of a specified PID.
  • -u user: Trace processes belonging to a specific user.
  • -V n: Specify the number of events to summarize per line (default: 1).
  • -w: Wait for the traced process to exit.
  • -x events: Exclude specified events from tracing.
  • -z events: Enable tracing of additional events (e.g., -z syscalls:all).

Examples

Simple Trace:

pstrace -p 1234

Filter Events by Syscall:

pstrace -e syscall:read

Group Events by PID:

pstrace -g pid

Save Trace to File:

pstrace -o trace.dat -p 1234

Common Issues

  • No output: Ensure that the traced process is running. Check if the -p option is specified correctly.
  • Truncated output: The trace length may have been exceeded. Use the -L option to increase the limit.
  • Permission denied: Make sure you have sufficient permissions to trace the process. Running pstrace as root may be necessary.

Integration

pstrace can be combined with other Linux commands to analyze results. For example:

  • Summarize Events: pstrace -p 1234 | awk '{print $1, $4}'
  • Filter Events by Duration: pstrace -p 1234 | grep "syscall:" | awk '{if ($2 > 10000) print}'

Related Commands

  • strace: Trace system calls and signals for a process.
  • ltrace: Trace library calls for a process.
  • ftrace: Trace kernel events and functions.