Python | os.ttyname() 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.ttyname() method in Python is used to get the terminal device associated with the specified 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. It 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. These file descriptors i.e 0 (stdin), 1 (stdout), and 2 (stderr) are standard file descriptors used by our programs. Further files opened by the current process will get the value 3, 4, 5 an so on.

Note: This method is only available on UNIX platforms and an exception is raised if the specified file descriptor is not associated with any terminal device.

Syntax: os.ttyname(fd)

Parameter:
fd: A file descriptor

Return Type: This method returns a string value which represents the terminal device associated with the specified file descriptor fd.

Code #1: Use of os.ttyname() method to get the terminal device associated with a file descriptor.

# Python program to explain os.ttyname() method

# importing os module
import os


# Standard file descriptors
# i.e 0 (stdin), 1 (stdout), and 2 (stderr)
# are used by our program
# Get the terminal device
# associated with these file descriptor
print("Terminal device associated with:")
print("Standard input:", os.ttyname(0))
print("Standard output:", os.ttyname(1))
print("standard error", os.ttyname(2))


# Open a new pseudo-terminal pair
# using os.openpty() method
# It will return master and slave
# file descriptor for
# pty ( pseudo terminal device) and
# tty ( native terminal device) respectively
master, slave = os.openpty()

# Get the terminal device
# associated with these file descriptor
print("Master:", os.ttyname(master))
print("Slave:", os.ttyname(slave))

Output:

Terminal device associated with:
Standard input: /dev/pts/0
Standard output: /dev/pts/0
standard error /dev/pts/0
Master: /dev/ptmx
Slave: /dev/pts/1

Code #2: If the specified file descriptor is not associated with any terminal device

# Python program to explain os.ttyname() method

# importing os module
import os


# If the specified file descriptor
# is not associated with any
# terminal device, then an exception
# will be raised. For example:

# Create a pipe using os.pipe() method
# It will return a pair of
# file descriptors (r, w) usable for
# reading and writing, respectively.
r, w = os.pipe()

# Get the terminal device associated
# with the file descriptor r or w
print(os.ttyname(r))

Output:

Traceback (most recent call last):
  File "getTerminalDevice.py", line 20, in 
    print(os.ttyname(r))
OSError: [Errno 25] Inappropriate ioctl for device

Code #3: Way to handle the above raised exception

# Python program to explain os.ttyname() method

# importing os module
import os


# Create a pipe using os.pipe() method
# It will return a pair of
# file descriptors (r, w) usable for
# reading and writing, respectively.
r, w = os.pipe()

# Method 1
# (using exception handling technique)
# Try to get the terminal device associated
# with the file descriptor r or w
try :
    print(os.ttyname(r))
except OSError as error :
    print(error)
    print("File descriptor is not associated with any terminal device")


# Method 2
# using os.isatty() method
# check first if the file descriptor w
# is associated with a tty(-like) device or not
# if it is then only get the terminal
# device associated with it
if os.isatty(w) :
    print(os.ttyname(w))
else :
    print("File descriptor is not associated with any terminal device")

Output:

[Errno 25] Inappropriate ioctl for device
File descriptor is not associated with any terminal device
File descriptor is not associated with any terminal device