Python | os.fchdir() method

OS module in Python provides functions for interacting with the operating system. OS comes under Python’s standard utility modules. This module provides a portable way of using operating system dependent functionality.

os.fchdir() method in Python is used to change the current working directory to the directory represented by the given file descriptor.

A file descriptor is small integer value that corresponds to a file or other input/output resource, such as a pipe or network socket. A File descriptor is an abstract indicator of a resource and act as handle to perform various lower level I/O operations like read, write, send etc.

For Example: Standard input is usually file descriptor with value 0, standard output is usually file descriptor with value 1 and standard error is usually file descriptor with value 2.
Further files opened by the current process will get the value 3, 4, 5 an so on.

os.fchdir() method is equivalent to os.chdir(file_descriptor) method.

Syntax: os.fchdir(fd)

Parameter:
fd: A file descriptor. The file descriptor must represent an opened directory not an open file.

Return Type: This method does not return any value.

Code #1: Use of os.fchdir() method to change the current working directory

# Python program to explain os.fchdir() method

# importing os module
import os


# Print the current working
# directory using os.getcwd() method
print("Current working directory:", os.getcwd())


# Path
path = "/home/ihritik/Documents"


# open the directory represented by
# the above given path and get
# the file descriptor associated
# with it using os.open() method
fd = os.open(path, os.O_RDONLY)


# Change the current working
# directory using os.fchdir() method
os.fchdir(fd)
print("Current working directory changed")


# Print the current working
# directory using os.getcwd() method
print("Current working directory:", os.getcwd())

Output:

Current working directory: /home/ihritik
Current working directory changed
Current working directory: /home/ihritik/Documents

Code #2: Possible errors while using of os.fchdir() method

# Python program to explain os.fchdir() method

# importing os module
import os


# Path
path = "/home/ihritik/Documents/file.txt"

# open the above path and get
# the file descriptor associated
# with it using os.open() method
fd = os.open(path, os.O_RDONLY)


# The file descriptor must
# represent an open file
# instead of an opened directory
# The method will raise
# 'NotADirectoryError' exception

# Change the current working
# directory using os.fchdir() method
os.fchdir(fd)
print("Current working directory changed")


# Print the current working
# directory using os.getcwd() method
print("Current working directory:", os.getcwd())

Output:

Traceback (most recent call last):
  File "changeDir.py", line 24, in 
    os.fchdir(fd)
NotADirectoryError: [Errno 20] Not a directory

Code #3: Handling possible errors while using of os.fchdir() method

# Python program to explain os.fchdir() method

# importing os module
import os


# Path
path = "/home/ihritik/Desktop/file.txt"

# try opening the above path and get
# the file descriptor associated
# with it using os.open() method
try :
    fd = os.open(path, os.O_RDONLY)

    # Try Changing the current working
    # directory using os.fchdir() method
    try :
        os.fchdir(fd)
        print("Current working directory changed")

        # Print the current working
        # directory using os.getcwd() method
        print("Current working directory:", os.getcwd())


    # Catch exceptions
    # If file descriptor does
    # not represents a directory
    except NotADirectoryError:
        print("The given file descriptor does \
not represent a directory")


# Catch exceptions
# If path does not exists
except FileNotFoundError:
    print("Path does not exists")

# If there is any permission
# related issue while opening
# the given path
except PermissionError:
    print("Permission denied")

Output:

The given file descriptor does not represent a directory