How can I use sudo to check if a file exists?
Solution 1:
if sudo test -f "/path/to/file"; then
echo "FILE EXISTS"
else
echo "FILE DOESN'T EXIST"
fi
test man page
To complete things, on the opposite side, if you want to check from root if a file or directory is readable for a certain user you can use
if sudo -u username test -f "/path/to/file"; then
echo "FILE EXISTS"
else
echo "FILE DOESN'T EXIST"
fi
Solution 2:
What you're describing should work fine - as long as you're using absolute paths, and -f
("File exists and is a regular file") is really the test you want to perform.
I see a trailing /
in what you posted in your question - Are you testing for a directory? That should be -d
, or simply -e
("Something exists with that name - regardless of type")
Also note that unless something along the way is not readable test
([
) should be able to tell you if a file owned by root exists or not (e.g. [ -f /root/.ssh/known_hosts ]
will probably fail, because the /root/.ssh directory isn't (or at least shouldn't be) readable by a normal user. [ -f /etc/crontab ]
should succeed).
Solution 3:
Adding to the other answers, distinguishing between the test or sudo authentication failing could be done by first running sudo true
. Most sudo implementations I know of won't require re-authentication within a short period.
For example:
if sudo true; then
if sudo test -f "/path/to/file"; then
echo "FILE EXISTS"
else
echo "FILE DOESN'T EXIST"
fi
else
echo "SUDO AUTHENTICATION FAILED"
fi