Displaying free disk space and memory

kanik · 08-19-2008, 05:44 PM

Hey, I need to display the free disk space in the /tmp folder and the free memory of the computer.
I'm using the following commands right now:

df -h /tmp
free -t -m

These give me a column of info like:

Filesystem Size Used Avail Use% Mounted on
tmpfs 2.0G 188K 2.0G 1% /tmp

But I only need to display the avail memory. I tried using the cut function to do so but wasn't able to do it.

So how do I do this? It can be done in the terminal or as a part of a C++ code.

Cheers
--Kanik

raconteur · 08-19-2008, 06:11 PM

free -t -m reports:

Code:

bash-3.1$ free -t -m
             total       used       free     shared    buffers     cached
Mem:           438        432          6          0        263         84
-/+ buffers/cache:         83        355
Swap:          172          2        170
Total:         611        434        176
bash-3.1$

so a simple parse would display the free memory:

Code:

bash-3.1$ free -t -m | egrep Mem | awk '{print $4}'
6
bash-3.1$

Unless I misunderstand what it was you were looking for...

kanik · 08-19-2008, 07:38 PM

Thats exactly what I was looking for. Thanks a lot!!

syg00 · 08-19-2008, 07:43 PM

If that's all you're looking for, might be easier to grep /proc/meminfo

kanik · 08-19-2008, 10:23 PM

Quote:

Originally Posted by syg00

If that's all you're looking for, might be easier to grep /proc/meminfo

Cheers, I'll try that method as well.

I'm also having a problem with converting the obtained memory/free disk space to string. I'm using this code:

PHP Code:



string DiskSensor::readSensorValue()
  {
string diskspace;  
diskspace = system("df /tmp | egrep tmpfs | awk '{print $4}'");
return diskspace;
  }
// Return a name for our sensor
string DiskSensor::getSensorTitle()
  {
  return "Free Disk Space";
  }


// Return the value read by the sensor
string DiskSensor::getSensorValue()
  {
  return readSensorValue();
  }

And in another file linked to this:

PHP Code:



  cout << "Sensor Title is: " << disksensor.getSensorTitle() << endl;
  cout << "Sensor Value is: " << disksensor.getSensorValue() << endl;

And I get this as output:

PHP Code:



Sensor Title is: Free Disk Space
2096984
Sensor Value is:

When I want :

PHP Code:



Sensor Title is: Free Disk Space
Sensor Value is:2096984 kB

So how can I fix the string and how do I add a "kB" at the end of the disk space?

Cheers
--Kanik

raconteur · 08-20-2008, 11:35 AM

Using the system() call is rarely necessary...

For example, the disk space info can be obtained directly using statfs()
And the free memory info is available via getrusage() and/or getrlimit()

hth

vharishankar · 08-20-2008, 12:16 PM

I second that. Use C calls (preferably standard POSIX calls) when available to system() calls with shell parameters. It is more portable.

kanik · 08-20-2008, 10:29 PM

I can't seem to get the getrusage command working. I'm more familiar with the system command so I would rather do it that way. So is this the right way to make the output from system command to a string and return it?

PHP Code:



string diskspace;   
diskspace = system("df /tmp | egrep tmpfs | awk '{print $4}'"); 
return diskspace;

Thanks

raconteur · 08-21-2008, 11:15 AM

Nope, that won't work.

system() only returns the exit status of the shell command, meaning it will only tell you whether the command succeeded or not. The output of the command will not be captured.

There are several ways to do that, but again, it is more work than it is worth.

kanik · 08-23-2008, 10:59 PM

Ok. Is there a way to put the output from the system(...) command into a text file? cuz if I can do that I know the rest...

kanik · 08-24-2008, 10:22 PM

Nevermind, I figured it out. Just added a ">abc.txt" at the end.
Thanks for the help!