Solved

Getting Environment Variables of Another User in C++ in Unix?

Posted on 2010-09-24
3
624 Views
Last Modified: 2012-08-13
Dear experts,

I have a process running in UNIX. I want the process to get the environment variables of a user other than the user in which it is running. Then I will run some of its threads with the environment of that another user. How can I achieve this?

BR,
0
Comment
Question by:GurcanK
3 Comments
 
LVL 78

Assisted Solution

by:arnold
arnold earned 200 total points
ID: 33755397
If you want to run an under the effective rights of another user, you have to switch to the effective user's settings. The environment variables are definable and vary depending on what the user has configured under their shell.

Are you spawning the thread using fork?

Have a look at any daemon application, http, etc. and you see that while the process starts running as root it then continues to run under a user with lower level rights.

I.e. you can use execv with fork etc.
http://www.google.com/url?sa=t&source=web&cd=6&ved=0CC0QFjAF&url=https%3A%2F%2Fwww.securecoding.cert.org%2Fconfluence%2Fdownload%2Fattachments%2F26017980%2F07%2BUNIX%2BPermissions%2Band%2BPrivileges.pdf%3Fversion%3D1%26modificationDate%3D1238607959000&rct=j&q=unix%20programming%20fork%20drop%20privileges&ei=w8-cTI3eKIWKlwemhvnVCg&usg=AFQjCNF4mU4EeSAzTfDSBTdkFtRF_7QMXA&cad=rja

http%3A%2F%2Fwww.cs.uga.edu%2F~eileen%2F1730%2FNotes%2Fprocesses-UNIX.ppt&rct=j&q=unix%20programming%20fork%20drop%20privileges&ei=w8-cTI3eKIWKlwemhvnVCg&usg=AFQjCNFHbm7rVc-AW71bJ6okEqEeOJV3sA&cad=rja

etc.
get yourself an account on www.informit.com and you may be able to use one of the C++ programming references.

There are other similar resources where you can access various books to get an example.
0
 
LVL 86

Accepted Solution

by:
jkr earned 300 total points
ID: 33755665
The easiest way would be to launch a shell to execute an 'export' command that list all environment variables. From your other Q I understand that your process is running as 'root', so you could use
#include <iostream>
#include <vector>
using namespace std;

#include <stdlib.h>

#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>

int run_cmd ( const char* pCmd, vector<string>& vOutput) {

  FILE *fp;
  int status;
  char path[PATH_MAX];

  fp = popen(pCmd, "r");
 // if (fp == NULL)
    /* Handle error */;

  while (fgets(path, PATH_MAX, fp) != NULL)
      printf("%s", path);

  status = pclose(fp);
  if (status == -1) {
    /* Error reported by pclose() */

  } else {

    /* Use macros described under wait() to inspect `status' in order
       to determine success/failure of command executed by popen() */
  }
return 0;
}

int main () {

  vector<string> vOutput;

  run_cmd("su -l OtherUser csh -c export",vOutput);

  // now vOutput contains all environment variables

  return 0;
}

Open in new window

0
 

Author Closing Comment

by:GurcanK
ID: 33763287
The comments were satisfactory.
0

Featured Post

Announcing the Most Valuable Experts of 2016

MVEs are more concerned with the satisfaction of those they help than with the considerable points they can earn. They are the types of people you feel privileged to call colleagues. Join us in honoring this amazing group of Experts.

Question has a verified solution.

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

Templates For Beginners Or How To Encourage The Compiler To Work For You Introduction This tutorial is targeted at the reader who is, perhaps, familiar with the basics of C++ but would prefer a little slower introduction to the more ad…
I have been running these systems for a few years now and I am just very happy with them.   I just wanted to share the manual that I have created for upgrades and other things.  Oooh yes! FreeBSD makes me happy (as a server), no maintenance and I al…
Learn several ways to interact with files and get file information from the bash shell. ls lists the contents of a directory: Using the -a flag displays hidden files: Using the -l flag formats the output in a long list: The file command gives us mor…
In a previous video, we went over how to export a DynamoDB table into Amazon S3.  In this video, we show how to load the export from S3 into a DynamoDB table.

735 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