How to find location of executable on Linux when normal methods fail?
In another question, the answer states that on Unixes with /proc
, the really straight and reliable way is to readlink("/proc/self/exe", buf, bufsize)
and it then proceeds to give backup solutions as follows:
On Unixes without /proc (i.e. if above fails):
- If argv[0] starts with "/" (absolute path) this is the path.
- Otherwise if argv[0] contains "/" (relative path) append it to cwd (assuming it hasn't been changed yet).
getcwd(buf, bufsize); strncat(buf, "/", bufsize-strlen(buf)-1); strncat(buf, argv[0], bufsize-strlen(buf)-1);
- Otherwise search directories in
$PATH
for executableargv[0]
.
Afterward it may be reasonable to check whether the executable isn't actually a symlink. If it is resolve it relative to the symlink directory.
Now in my case, unfortunately, none of the above works:
/proc/self/exe exi开发者_JS百科sts
but fail toreadlink()
due to permission denied errno 13.- The
argv[0]
has no/
for absolute or relative path. - The
$PATH
does not contain the executable found inargv[0]
.
It appears this issue is faced also when sgid applications run. In my case, it is not sgid, but an inetd launch.
The best way to solve this is in the /etc/xinetd.d/myApp configuration file, to add an environment variable that specifies the location of the binary like this:
service myApp
{
socket_type = stream
protocol = tcp
wait = no
user = root
server = /usr/local/bin/myAppd
env = MY_APP_HOME=/usr/local/bin
port = 2354
disable = no
}
Then, if /proc/self/exe is permission denied, check for the env varible and use it instead.
Try looking in /proc from a suid binary.
I think that the answer is: give up.
Ask the user to pass the install directory (or whatever you are looking for) as a command line argument.
As a last resort, parse the /etc/xinetd.d/myApp file to pull out the server line which includes the complete path to the executable summoned via inetd.
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