Solved

Execute program and capture output

Posted on 2001-08-15
8
243 Views
Last Modified: 2009-07-29
Hi

I can't quite figure out how to execute an external application and get the output provided by this app for further processing;

Ex:

my_buffer = exec("NET USER");
processusers( (char *)my_buffer );

Hope somebody can help..

0
Comment
Question by:ToHo
8 Comments
 
LVL 6

Expert Comment

by:kotan
ID: 6387426
you can redirect the output to a file.
Then read the file to get output.

exec("NET USER > out.txt");

read("out.txt");
0
 
LVL 2

Author Comment

by:ToHo
ID: 6387625
Yeah, I know, but I was thinking more of redirecting the standard output (con) to my own stream or buffer. This way I don't have to go via another file.
0
 
LVL 5

Expert Comment

by:proskig
ID: 6387662
0
 
LVL 2

Expert Comment

by:bkdc
ID: 6387774
Check out the MSDN

This deals with consoles
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/fileio/hh/winbase/conchar_3vg3.asp

and

this deals with processes

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dllproc/hh/winbase/prothred_3mgj.asp

The most interesting function is CreateProcess()

If you "really" need help I'll give you a sample; currently I'm using QNX and is quite impossible to write a program for you on my machine
0
Is Your Active Directory as Secure as You Think?

More than 75% of all records are compromised because of the loss or theft of a privileged credential. Experts have been exploring Active Directory infrastructure to identify key threats and establish best practices for keeping data safe. Attend this month’s webinar to learn more.

 
LVL 86

Accepted Solution

by:
jkr earned 100 total points
ID: 6387830
/* POPEN.C: This program uses _popen and _pclose to receive a
 * stream of text from a system process.
 */

#include <stdio.h>
#include <stdlib.h>

void main( void )
{

   char   psBuffer[128];
   FILE   *netuser;

   /* Run 'net user' so that it writes its output to a pipe. Open this
    * pipe with read text attribute so that we can read it
    * like a text file.
    */
   if( (netuser = _popen( "net user" )) == NULL )
      exit( 1 );

   /* Read pipe until end of file. End of file indicates that
    * 'net user' closed its standard out (probably meaning it
    * terminated).
    */
   while( !feof( netuser ) )
   {
      if( fgets( psBuffer, 128, netuser ) != NULL )
         printf( psBuffer );
   }

   /* Close pipe and print return value of 'net user'. */
   printf( "\nProcess returned %d\n", _pclose( netuser ) );
}
0
 
LVL 4

Expert Comment

by:AssafLavie
ID: 6388960
// Open the target file. Specify the ability to inherit the handle.
SECURITY_ATTRIBUTES sa = { sizeof(SECURITY_ATTRIBUTES), NULL, TRUE };
HANDLE hOutputFile = CreateFile("OutputFile", GENERIC_ALL, 0, &sa, CREATE_ALWAYS, 0, 0); // Tell the new process to use the file as the standard output.
STARTUPINFO si = {0};
si.dwFlags = STARTF_USESTDHANDLES;
si.hStdOutput = hOutputFile; // Start the process.
PROCESSINFORMATION pi = {0};
HANDLE hProcess = CreateProcess("file.exe", NULL, NULL, NULL, TRUE, 0, NULL, NULL, &si, &pi); // Don't forget.
CloseHandle(hOutputFile);
CloseHandle(hProcess);
0
 
LVL 4

Expert Comment

by:AssafLavie
ID: 6388963
oops, it got all messed up. You can read it here:
http://www.geocities.com/assaflavie/faqs/redirecting_std_output.txt
0
 
LVL 2

Author Comment

by:ToHo
ID: 6389609
Thanks everybody.

The solution proposed by jkr provided exactly what I was trying to do, so I'm awarding the points to him.

Note: _popen( "net user" ) should read _popen( "net user", "r");
0

Featured Post

Is Your Active Directory as Secure as You Think?

More than 75% of all records are compromised because of the loss or theft of a privileged credential. Experts have been exploring Active Directory infrastructure to identify key threats and establish best practices for keeping data safe. Attend this month’s webinar to learn more.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Errors will happen. It is a fact of life for the programmer. How and when errors are detected have a great impact on quality and cost of a product. It is better to detect errors at compile time, when possible and practical. Errors that make their wa…
Written by John Humphreys C++ Threading and the POSIX Library This article will cover the basic information that you need to know in order to make use of the POSIX threading library available for C and C++ on UNIX and most Linux systems.   [s…
The viewer will learn additional member functions of the vector class. Specifically, the capacity and swap member functions will be introduced.
The viewer will be introduced to the member functions push_back and pop_back of the vector class. The video will teach the difference between the two as well as how to use each one along with its functionality.

896 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

13 Experts available now in Live!

Get 1:1 Help Now