Python |os.ftruncate()方法

Python os.ftruncate()方法截断与文件描述符fd对应的文件，使其在大小上最多为长度字节。

语法:os.ftruncate(fd, length)

参数:

fd:这是要截断的文件描述符。

length:这是要截断的文件的长度。

返回值:此方法不返回任何值。

示例1

使用os.ftruncate()方法截断文件

# 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)

输出:

b'Geeks'

示例2

使用os.ftruncate()方法截断文件

# 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)

输出: