function::task_fd_lookup - Linux

Overview

function::task_fd_lookup is a command used in the Linux kernel for looking up file descriptors associated with a task. It is primarily used for debugging and diagnostic purposes, providing information about open files and their status within a specific task.

Syntax

function::task_fd_lookup [options] <task_pid>

Parameters

  • <task_pid>: Task ID for which file descriptors are to be looked up.

Options/Flags

| Option | Description |
|—|—|
| -c | Count open file descriptors. |
| -d | Dump file descriptor information in detail. |
| -D | Dump all file descriptors. |
| -f | Force lookup, even if task is not running. |
| -h | Display usage help. |
| -k | Use kernel symbols for dump output. |
| -l | List open file descriptor numbers. |
| -m | Dump memory mapped file information. |
| -n | Display file descriptor numbers only. |
| -P | Dump poll table information. |
| -r | Dump read-only file descriptor information. |
| -s | Dump signal handlers. |
| -T | Dump thread group information. |
| -t | Dump threads. |
| -u | Dump user space information. |
| -v | Verbose output. |

Examples

Simple Usage:

function::task_fd_lookup 1234

This lists the file descriptors open by the task with ID 1234.

Count Open File Descriptors:

function::task_fd_lookup -c 1234

This counts and displays the number of open file descriptors for the task.

Detailed Information Dump:

function::task_fd_lookup -D 1234

This dumps detailed information about all file descriptors open by the task.

Common Issues

  • Permission denied: Ensure you have sufficient privileges to access the task information.
  • Task not found: The specified task ID may not exist or the task may have terminated before the command was executed.

Integration

function::task_fd_lookup can be integrated with other commands or tools for advanced debugging tasks:

  • ps: ps -p <task_pid> -aux | function::task_fd_lookup <task_pid>: Display process information and open file descriptors for a specific task.
  • strace: strace -p <task_pid> | function::task_fd_lookup <task_pid>: Trace system calls and correlate them with open file descriptors.
  • lsof: lsof -p <task_pid> | function::task_fd_lookup <task_pid>: List open files by a specific task and cross-reference them with the file descriptor information.

Related Commands

  • lsof: Lists open files by process.
  • strace: Traces system calls made by a process.
  • pmap: Displays memory map of a process.