Good morning all!
So I'm using a ramfs for temporary files, thank you whoever designed that,
it works great!
I can mkdir, mount, chmoud, readand write and then umount the thing from the
command line just fine.
What I need now is some method from within my C/C++ code to determine if the
ramfs is mounted, if not, then mount it so I can use it and unmount it when
I'm done, without making a system call.
Can this be done? Is there any access to mount/unmount from C/C++?
-b
On Tue, Sep 22, 2009 at 09:04:15AM -0700, Brian McGrew wrote:
> Good morning all!
>
> So I'm using a ramfs for temporary files, thank you whoever designed that,
> it works great!
>
> I can mkdir, mount, chmoud, readand write and then umount the thing from the
> command line just fine.
>
> What I need now is some method from within my C/C++ code to determine if the
> ramfs is mounted, if not, then mount it so I can use it and unmount it when
> I'm done, without making a system call.
You mean without using system(3), right? System call is how your program
interacts with the outside world.
The relevant system calls are:
- mount(2): mount("none", "/mnt", "ramfs", 0, NULL);
- umount(2): umount("/mnt");
The function(section) is the standard Unix way of specifying the manual
section of the function. Use it like this:
$ man 2 mount
About checking whether it is already mounted, you could parse the file
/proc/mounts, or check the result of statfs(2).
Regards,
Luciano Rocha
--
Luciano Rocha <[email protected]>
Eurotux Inform?tica, S.A. <http://www.eurotux.com/>
On 09/22/2009 07:04 PM, Brian McGrew wrote:
> Good morning all!
>
> So I'm using a ramfs for temporary files, thank you whoever designed that,
> it works great!
>
> I can mkdir, mount, chmoud, readand write and then umount the thing from the
> command line just fine.
>
> What I need now is some method from within my C/C++ code to determine if the
> ramfs is mounted, if not, then mount it so I can use it and unmount it when
> I'm done, without making a system call.
>
> Can this be done? Is there any access to mount/unmount from C/C++?
I suppose looking at the source code of the 'mount' utility could prove
very enlightening. You can find it at:
http://www.kernel.org/pub/linux/utils/util-linux-ng
On 09/22/2009 08:13 PM, Nikos Chantziaras wrote:
> On 09/22/2009 07:04 PM, Brian McGrew wrote:
>> Good morning all!
>>
>> So I'm using a ramfs for temporary files, thank you whoever designed
>> that,
>> it works great!
>>
>> I can mkdir, mount, chmoud, readand write and then umount the thing
>> from the
>> command line just fine.
>>
>> What I need now is some method from within my C/C++ code to determine
>> if the
>> ramfs is mounted, if not, then mount it so I can use it and unmount it
>> when
>> I'm done, without making a system call.
>>
>> Can this be done? Is there any access to mount/unmount from C/C++?
>
> I suppose looking at the source code of the 'mount' utility could prove
> very enlightening. You can find it at:
>
> http://www.kernel.org/pub/linux/utils/util-linux-ng
Also, "man 2 mount" will provide docs about the the mount() function in
<sys/mount.h>. If for some reason that man page isn't provided in your
system, you can find a copy at:
http://linux.die.net/man/2/mount
On 22.09.2009 09:04, Brian McGrew wrote:
> Good morning all!
>
> So I'm using a ramfs for temporary files, thank you whoever designed that,
> it works great!
>
> I can mkdir, mount, chmoud, readand write and then umount the thing from the
> command line just fine.
>
> What I need now is some method from within my C/C++ code to determine if the
> ramfs is mounted, if not, then mount it so I can use it and unmount it when
> I'm done, without making a system call.
>
> Can this be done? Is there any access to mount/unmount from C/C++?
The "/bin/mountpoint"-util appears to stat the mountpoint and it's
parent directory and compares if they have the same device-no (st_dev).
If they are different, then something is mounted.
Bis denn
--
Real Programmers consider "what you see is what you get" to be just as
bad a concept in Text Editors as it is in women. No, the Real Programmer
wants a "you asked for it, you got it" text editor -- complicated,
cryptic, powerful, unforgiving, dangerous.
> You mean without using system(3), right? System call is how your program
> interacts with the outside world.
>
> The relevant system calls are:
> - mount(2): mount("none", "/mnt", "ramfs", 0, NULL);
> - umount(2): umount("/mnt");
>
Thanks for the help! I'm getting there. Considering the following:
If (mount("ramfs", rd_path, "ramfs", MS_NOEXEC | MS_NOSUID, "size=2000m") <
0) {
strerror(errno);
} else {
std::cout << "mounted";
}
Works great! Thank you. However, even though the filesystem is mounted and
/bin/mountpoint confirms it's a mountpoint, I do not see the mountpoint
listed in /etc/mtab.
Also, according to what I've read about ramfs, the size is supposed to be
limited to size=, however, I can cat /dev/zero until the box it out of
memory (and swap).
I think I'm just missing something and google's not helping a whole lot
since ramfs isn't the most popular subject today.
Thanks,
-b
mount(2) (i.e. the system-call/library function) does not update /etc/mtab, IIRC...
mount(8) (the command-line utility) does...
In either case, I would expect the mount to show up in /proc/mounts (assuming
/proc is mounted).
On 09/22/2009 12:30 -0700, Brian McGrew wrote:
>> > You mean without using system(3), right? System call is how your program
>> > interacts with the outside world.
>> >
>> > The relevant system calls are:
>> > - mount(2): mount("none", "/mnt", "ramfs", 0, NULL);
>> > - umount(2): umount("/mnt");
>> >
>>
>> Thanks for the help! I'm getting there. Considering the following:
>>
>> If (mount("ramfs", rd_path, "ramfs", MS_NOEXEC | MS_NOSUID, "size=2000m") <
>> 0) {
>> strerror(errno);
>> } else {
>> std::cout << "mounted";
>> }
>>
>> Works great! Thank you. However, even though the filesystem is mounted and
>> /bin/mountpoint confirms it's a mountpoint, I do not see the mountpoint
>> listed in /etc/mtab.
>>
>> Also, according to what I've read about ramfs, the size is supposed to be
>> limited to size=, however, I can cat /dev/zero until the box it out of
>> memory (and swap).
>>
>> I think I'm just missing something and google's not helping a whole lot
>> since ramfs isn't the most popular subject today.
>>
>> Thanks,
>>
>> -b
>>
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