Python os.fchdir() Method

The os.fchdir() method in Python is used to change the current working directory to that represented by a file descriptor. A file descriptor is a low-level handle for an open file or directory.

Syntax

os.fchdir(fd)

Parameters

fd: It is a file descriptor.

Return value

It does not return any value.

Example 1: Basic Usage of os.fchdir()

import os

# Open a directory and get a file descriptor
dir_fd = os.open(
  '/Users/krunallathiya/Desktop/Code/pythonenv/env/dir', os.O_RDONLY)

# Change the current working directory to the given directory
os.fchdir(dir_fd)

# Current directory is now '/path/to/directory'
print("Current Working Directory: ", os.getcwd())

# Close the file descriptor
os.close(dir_fd)

Output

Current Working Directory: /Users/krunallathiya/Desktop/Code/pythonenv/env/dir

This is now becoming our current working directory:

Output of os.fchdir() function

If the file descriptor is invalid or does not represent a directory, an error (such as OSError) will be raised.

It’s essential to close the file descriptor using os.close(fd) after it is no longer needed to avoid resource leaks.

The change in the current working directory is process-wide, affecting all process threads. It’s essential to be aware of this in multi-threaded applications.

Example 2: Combining os.fchdir() with Other OS Operations

import os

# Open a directory and get a file descriptor
dir_fd = os.open(
  '/Users/krunallathiya/Desktop/Code/pythonenv/env/dir', os.O_RDONLY)

# Change the current working directory to the given directory
os.fchdir(dir_fd)

# List files in the current directory
print("Files in current working directory:")
for file in os.listdir('.'):
  print(file)

# Revert back to the original directory
os.close(dir_fd)

Output

Files in current working directory:
file.txt

Output of getting a file in current working directory

One thing to note is that the process should have the necessary permissions to change the current working directory to the target directory.

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