Re: [Fwd: Re: How to use a shell command in an application?]

["Sandeep K.S" <sandeep@xxxxxxxxxxxxxxx>]

Yasmine Habib wrote:

Hi,
    thank you so much for your e-mail but i tried this code to pipe
the input from "ps" into an output file then read from it but the
problem is that the output file is not flushed. that is; it is being
written over which results in incorrect information.. can you help me
with a correct code to take the information from ps and write it to a
file to be used later in my program?
  

Dont pipe it to the file, but do ' ps > output_file'. This will flush out all teh existing contents of the file and write the latest output into the file

sandeep

thank you so much 






On 5/10/05, Sandeep Tyagi <sandeepktyagi@xxxxxxxxx> wrote:
  

use popen system call. it will give u the flexibility to read the out put.
# man popen

On 5/10/05, Sandeep <sandeep@xxxxxxxxxxxxxxx> wrote:
    

---------- Forwarded message ----------
From: "Sachin Rane" <sachin.trane@xxxxxxxxx>
To: "'Sandeep'" <sandeep@xxxxxxxxxxxxxxx>
Date: Tue, 10 May 2005 11:05:50 -0700
Subject: RE: How to use a shell command in an application?
Hi Sandeep,

Could you forward my reply to 'kernelnewbies@xxxxxxxxxxxx' and  'Yasmine
Habib'?
This mail may not reach them because of firewall settings.

/****************************************************/
// Below is the example of executing shell command
// "cat > /proc/iomem" from application
//
/****************************************************/

#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>

int main(void)
{
       int fd_exec;
       char *const arg_list[]= {
               "cat",
               "/proc/iomem",
               NULL
       };
       if(fork() == 0)
       {
       /*** Please note below 3 statements can be replaced by the above two
          statements viz close(1) & open(...) ***/
               fd_exec = open("/tmp/iomemdump", O_CREAT | O_WRONLY );
               dup2(fd_exec,1);
               close(fd_exec);
               execvp("/bin/cat",arg_list);
       }
       printf("Hello\n");
       return 0;
}

Regards,
Sachin Rane

-----Original Message-----
From: kernelnewbies-bounce@xxxxxxxxxxxx
[mailto:kernelnewbies-bounce@xxxxxxxxxxxx]On Behalf Of Sandeep
Sent: Monday, May 09, 2005 10:07 PM
To: Yasmine Habib
Cc: kernelnewbies@xxxxxxxxxxxx
Subject: Re: How to use a shell command in an application?

Yasmine Habib wrote:

      

How can i use a shell command inside a program or application? in
other words, i am writing a small scheduler that needs to get the
current cpu usage/utliization of a processor at a certain time. using
"top", "free", "vmstat" provide me with required information but just
as a display when used as a shell command. i need the code to be
written inside my scheduler.


        

You can try it out with the system( ) call. This will give you the
flexibility to run any command that u can run in the shell.

sandeep

      

Thank you

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