Python | os.fchown() 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.

All functions in os module raise OSError in the case of invalid or inaccessible file names and paths, or other arguments that have the correct type, but are not accepted by the operating system.

os.fchown() method in Python is used to change the owner and group id of the file associated with the specified file descriptor to the specified numeric owner id (UID) and group id (GID). This method is equivalent to os.chown(fd, uid, gid) method.



Note: os.fchown() method is available only on UNIX platforms and the functionality of this method is typically available only to the superuser or a privileged user.

Syntax: os.fchown(fd, uid, gid)

Parameters:
fd: A file descriptor representing the file whose uid and gid is to be set
uid: An integer value representing the owner id to be set for the file.
gid: An integer value representing the group id to be set for the file. To leave any one of the ids unchanged, set it to -1.

Return Type: This method does not return any value.

Code #1: Use of os.fchown() method

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# Python program to explain os.fchown() method 
    
# importing os module 
import os
  
# File
filename = "file.txt"
  
  
# Open the file and get the 
# file descriptor associated
# with it using os.open() method
fd = os.open(filename, os.O_RDWR)
  
# Print the current owner id
# and group id of the file
  
# os.stat() method will return a 
# 'stat_result’ object of
# ‘os.stat_result’ class whose
# 'st_uid' and 'st_gid' attributes
# will represent owner id and group id
# of the file respectively 
print("Owner id of the file:", os.stat(fd).st_uid)
print("Group id of the file:", os.stat(fd).st_gid) 
  
  
# Change the owner id and 
# the group id of the file
# associated with the file descriptor
# using os.fchown() method
uid = 200
gid = 300
os.fchown(fd, uid, gid)
print("\nOwner and group id of the file changed")
  
   
# Print the owner id
# and group id of the file
print("\nOwner id of the file:", os.stat(fd).st_uid)
print("Group id of the file:", os.stat(fd).st_gid) 

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Output:
os.fchown() method terminal output

Code #2: Use of os.fchown() method to set any one id and leave other unchanged

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# Python program to explain os.fchown() method 
    
# importing os module 
import os
  
# File
filename = "file.txt"
  
# Open the file and get the 
# file descriptor associated
# with it using os.open() method
fd = os.open(filename, os.O_RDWR)
  
# Print the current owner id
# and group id of the file
  
# os.stat() method will return a 
# 'stat_result’ object of
# ‘os.stat_result’ class whose
# 'st_uid' and 'st_gid' attributes
# will represent owner id and group id
# of the file respectively 
print("Owner id of the file:", os.stat(fd).st_uid)
print("Group id of the file:", os.stat(fd).st_gid) 
  
  
# Change only group id of 
# the file and leave owner id
# unchanged
  
# set id as -1 to leave
# it unchanged
uid = -1
gid = 1000
os.fchown(fd, uid, gid)
print("\ngroup id of the file changed")
  
   
# Print the owner id
# and group id of the file
print("\nOwner id of the file:", os.stat(fd).st_uid)
print("Group id of the file:", os.stat(fd).st_gid) 

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Output:
os.fchown() method terminal output

Code #3: If the specified path is a symlink

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# Python program to explain os.fchown() method 
    
# importing os module 
import os
  
# File path
path = "./file.txt"
  
# Creating a symlink
# of the above path  
# using os.symlink() method
symlink = "./file(symlink).txt"
os.symlink(path, symlink)
  
# Open the symlink
# and get the file descriptor
# associated with it using
# os.open() method
fd = os.open(symlink, os.O_RDWR)
   
# Print the current owner id
# and group id of the file
# as well as the symlink pointing
# to the above specified file path 
print("Owner id of the file:", os.stat(path).st_uid)
print("Group id of the file:", os.stat(path).st_gid) 
  
print("Owner id of the symlink:", os.stat(symlink).st_uid)
print("Group id of the symlink:", os.stat(symlink).st_gid) 
  
# Change the owenership 
# of the symlink pointing 
# to the above file './file.txt'
uid = 600
gid = 700
os.fchown(fd, uid, gid)
print("\nOwner id and group id changed")
  
  
# Print the owner id
# and group id of the file
# as well as the symlink
print("\nOwner id of the file:", os.stat(path).st_uid)
print("Group id of the file:", os.stat(path).st_gid) 
  
print("Owner id of the symlink:", os.stat(symlink).st_uid)
print("Group id of the symlink:", os.stat(symlink).st_gid)
  
  
# As os.fchown() method
# follows symlink
# so, we can change the
# owner and group id 
# through a symlink 

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Output:
os.fchown() method terminal output

Reference: https://docs.python.org/3/library/os.html



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