12.2. Taking a Screenshot

⁠12.2. Taking a Screenshot

To perform operations involving sending and receiving data from the software running on top of a virtualisation driver, we need to use streams.

For this example, we assume that we have a domain named 'TestDomain' running on the QEMU virtualisation driver.

⁠

Example 12.8. Looking up the domain

import sys, libvirt
conn = None
try:
    conn = libvirt.open("qemu:///system")
except libvirt.libvirtError as e:
    print(repr(e), file=sys.stderr)
    exit(1)
domain = conn.lookupByName('TestDomain')

We then create a stream, and take a screenshot. The 'screenshot' method returns the type of image that the screenshot is taken as. Different virtualisation drivers may produce different types of images.

⁠

Example 12.9. Use stream to take screenshot

stream = conn.newStream()
imageType = domain.screenshot(stream,0)

As the function 'virStreamRecv' (backend for the stream object’s 'recvAll' function) is not always supported, we can listen to our stream on a loop, writing as we go and checking to see if there’s any more data left to read:

⁠

Example 12.10. Reading data from stream

file = "Screenshot of " + dom.name()
fileHandler = open(file, 'wb')
streamBytes = stream.recv(262120)
while streamBytes != b'':
    fileHandler.write(streamBytes)
    streamBytes = stream.recv(262120)
fileHandler.close()
print('Screenshot saved as type: ' + imageType)

Once done, we can open our file and see that we have a screenshot of the virtual machine’s desktop. Success! Remember to finish the stream and close the virtualisation driver connection afterwards.

Full code in the example below.

⁠

Example 12.11. Taking a Screenshot

# Example-11.py
import sys
import libvirt

domName = 'TestAppliance'

conn = None
try:
    conn = libvirt.open("qemu:///system")
except libvirt.libvirtError as e:
    print(repr(e), file=sys.stderr)
    exit(1)

dom = None
try:
    dom = conn.lookupByName(domName)
except libvirt.libvirtError as e:
    print(repr(e), file=sys.stderr)
    exit(1)

stream = conn.newStream()

# This function supports up to three arguments:
#   stream, screen number and flags.
# We do not need to supply anything for the flags argument.
# The screen number is the sequential number of the screen
#   we want to take a screenshot of.

imageType = domain.screenshot(stream,0)

file = "Screenshot of " + dom.name()
fileHandler = open(file, ’wb’)
streamBytes = stream.recv(262120)

while streamBytes != b’’:
    fileHandler.write(streamBytes)
    streamBytes = stream.recv(262120)
fileHandler.close()

print(’Screenshot saved as type: ’ + imageType)
stream.finish()

conn.close()
exit(0)