Python | os.ftruncate() 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.ftruncate() method truncates the file corresponding to file descriptor fd, so that it is at most length bytes in size.

Syntax: os.ftruncate(fd, length)

Parameters:
fd: This is the file descriptor that is to be truncated.
length: This is the length of the file upto which file is to be truncated.

Return Value: This method does not returns any value.

Example #1 :
Using os.ftruncate() method to truncate a file

# Python program to explain os.ftruncate() method

# importing os module
import os

# path
path = 'C:/Users/Rajnish/Desktop/testfile.txt'

# Open the file and get
# the file descriptor associated
# with it using os.open() method
fd = os.open(path, os.O_RDWR|os.O_CREAT)

# String to be written
s = 'GeeksforGeeks'

# Convert the string to bytes
line = str.encode(s)

# Write the bytestring to the file
# associated with the file
# descriptor fd
os.write(fd, line)

# Using os.ftruncate() method
os.ftruncate(fd, 5)

# Seek the file from beginning
# using os.lseek() method
os.lseek(fd, 0, 0)

# Read the file
s = os.read(fd, 15)

# Print string
print(s)

# Close the file descriptor
os.close(fd)

Output:

b'Geeks'

Example #2 :
Using os.ftruncate() method to truncate a file

# Python program to explain os.ftruncate() method

# importing os module
import os

# path
path = 'C:/Users/Rajnish/Desktop/testfile.txt'

# Open the file and get
# the file descriptor associated
# with it using os.open() method
fd = os.open(path, os.O_RDWR|os.O_CREAT)

# String to be written
s = 'GeeksforGeeks - Computer Science portal'

# Convert the string to bytes
line = str.encode(s)

# Write the bytestring to the file
# associated with the file
# descriptor fd
os.write(fd, line)

# Using os.ftruncate() method
os.ftruncate(fd, 10)

# Seek the file from beginning
# using os.lseek() method
os.lseek(fd, 0, 0)

# Read the file
s = os.read(fd, 15)

# Print string
print(s)

# Close the file descriptor
os.close(fd)

Output:

b'GeeksforGe'