fopen called in daemon fails on system reboot.

samarthya · 04-23-2009, 04:46 AM

Hi!
I am facing a unusually simple problem with fopen(). The issue is when my daemon starts up with the machine and is forwarded a request from a client it fails to create a temporary file required to process the request. I located the issue with open with help of SYSLOG, now if i restart this daemon it starts working fine. Has anyone else faced it before?

I have set the permission using UMASK and also ensure the group id and session ID for the daemon.

The daemon tries to write a file under /root, which fails after machine reboot but succeeds when the daemon is explicitly restarted.

- Samarthya.

wje_lq · 04-23-2009, 08:24 PM

Two questions.

Do you specify the file as, for example,
Code:
```
/root/fred.txt
```
or do you specify it as
Code:
```
fred.txt
```
expecting the current directory to be
Code:
```
/root
```
?
What is the value of errno after the fopen() failure?

voyvf · 04-23-2009, 08:46 PM

Posting the daemon section, as well as the fopen section of the code could be helpful, assuming you're not using the int daemon(int nochdir, int noclose); function from unistd.h.

saurabh777 · 04-24-2009, 12:31 AM

I use absolute path

Code:

/root/a.txt

Even if i specify

Code:

./a.txt

is there an issue? because if i use

Code:

getcwd()

I get the /root as the current directory.

Thanks,
Samarthya

wje_lq · 04-24-2009, 01:42 AM

Please write a simple daemon which does this:

Open the file, using the same fopen() statement that you use in the real daemon.
If it succeeds, syslog that it succeeded.
If it fails, syslog that it failed and syslog the errno.

Then try this daemon at system reboot and then restart it explicitly.

Do they both fail? Both succeed? One succeed, and one fail?