Python: Check if a /dev/disk device exists
I am trying to write python script to find out if a disk device exists in /dev, but it always yield False. Any other way to do this?
I tried
>>> import os.path
>>> os.path.isfile("/dev/bsd0")
False
>>> os.path.exists("/dev/bsd0")
False
$ ll /dev
...
brw-rw---- 1 root disk 252, 0 Nov 12 21:28 bsd0
...
This was not rigorously tested, but seems to work:
import stat
import os.stat
def disk_exists(path):
try:
return stat.S_ISBLK(os.stat(path).st_mode)
except:
return False
Results:
disk_exists("/dev/bsd0")
True
disk_exists("/dev/bsd2")
False
Some unconventional situation is going on here.
os.path.isfile() will return True for regular files, for device files this will be False .
But as for os.path.exists() , documetation states that False may be returned if "permission is not granted to execute os.stat() ". FYI the implementation of os.path.exists is:
def exists(path):
"""Test whether a path exists. Returns False for broken symbolic links"""
try:
os.stat(path)
except OSError:
return False
return True
So, if os.stat is failing on you I don't see how ls could have succeeded ( ls AFAIK also calls stat() syscall). So, check what os.stat('/dev/bsd0') is raising to understand why you're not being able to detect the existence of this particular device file with os.path.exists , because using os.path.exists() is supposed to be a valid method to check for the existence of a block device file.