Python os.read() Method

Python os.read() Method

Imran Alam Jul-27, 2022 Python Python OS
  1. Syntax of os.read():
  2. Example Codes: Use the os.read() Method to Read a File
  3. Example Codes: Use the os.read() Method to Read the Entire File
  4. Example Codes: Use the os.read() Method to Read Input
  5. Example Codes: Possible Errors While Using the os.read() Method

The os.read() method is a built-in Python method used to read data from a file descriptor.

Syntax of os.read():

os.read(fd, n)

Parameters

fd This is the file descriptor to read from.
n This is the number of bytes to read.

Return

The os.read() method returns the data read from the file descriptor as a string.

Example Codes: Use the os.read() Method to Read a File

In the following example, the os.read() method is used to read 10 bytes from the file descriptor:

import os

fd = os.open("test.txt", os.O_RDONLY)

data = os.read(fd, 10)

print(data)

Output:

This is

Example Codes: Use the os.read() Method to Read the Entire File

In the following example, the os.read() method is used to read the entire contents of the file:

import os

fd = os.open("test.txt", os.O_RDONLY)

data = os.read(fd, os.path.getsize("test.txt"))

print(data)

Output:

This is demo data

Example Codes: Use the os.read() Method to Read Input

In the following example, the os.read() method is used to read data from the standard input:

import os

data = os.read(0, 10)

print(data)

Input:

data

Output:

b'data\r\n'

Example Codes: Possible Errors While Using the os.read() Method

Error Description
ValueError This occurs if the fd is not a valid file descriptor.
OSError This occurs if the fd is not open for reading.
IOError This error occurs if the fd is not open.

ValueError

import os

os.read(5, 10)

Output:

ValueError: 5 is not a valid file descriptor

OSError

import os

fd = os.open("test.txt", os.O_WRONLY)

os.read(fd, 10)

Output:

OSError: fd is not open for reading

IOError

import os

os.read(10, 10)

Output:

IOError: fd is not open

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