Thread: Setting an environment variable using setenv()

  1. #1
    Registered User
    Join Date
    Oct 2014

    Question Setting an environment variable using setenv()

    Hi, all!

    I'm trying to set an environmet variable using setenv() function. I'm able to print it when using getenv() within same program, but cannot see it with printenv command in bash after program exits. It seems like variable just set for the program execution time and not exported, how can I export it to be able to use it inside bash Thanks.

  2. #2
    Master Apprentice phantomotap's Avatar
    Join Date
    Jan 2008

    The environment block, for most operating systems, is designed such that changes to the environment are only inherited not propagated. The `setenv' function changes the environment only for the calling process and children. In other words, the behavior you are seeing is the intended behavior.

    The propagation of an environment the way you would like presents a major security issue. If you'd tell us about the platform and why you are trying to propagate a change to the environment, someone may be able to help you find a solution.

    “Salem Was Wrong!” -- Pedant Necromancer
    “Four isn't random!” -- Gibbering Mouther

  3. #3
    Unregistered User Yarin's Avatar
    Join Date
    Jul 2007
    Quote Originally Posted by kill'emall View Post
    how can I export it to be able to use it inside bash
    You can't; for the reason stated by Soma.

    I think that you are being misled by the name of the command "export".

    When you export an environment variable in bash, it is not back-propagating the envvar, it is simply setting it's own envvar, just the same as when your program calls setenv().
    To see what I mean, do this: Run bash. Run bash again. Export an envvar of your liking. Confirm that it's set. Exit bash. Check the envvar again, it will no longer be what you exported it as.

    The only way you can get all the programs to take on an envvar is by updating the users profile, and even then it won't take effect until all the processes are restarted from the new profile (that is, you log out and back in again)

  4. #4
    Registered User
    Join Date
    Nov 2012
    Quote Originally Posted by kill'emall View Post
    how can I export it to be able to use it inside bash Thanks.
    One possibility is to put the export commands into your $HOME/.bash_profile startup script.

  5. #5
    Registered User
    Join Date
    Oct 2014
    Thank's a lot for your responds. I'm reading a great book "Advanced Linux Programming" and trying to practice on one chapter that explains the environment. What I'm trying to do is to write the program that promts for a variables and sets or unsets them respectively. From the same book I know about the external environ variable. And I think modifying it is the way to make environment variable persistent.
    But I think my knowledge will not me allow to play with this in near future.

Popular pages Recent additions subscribe to a feed

Similar Threads

  1. Some advice in setting my Linux dev environment
    By Mario F. in forum General Discussions
    Replies: 19
    Last Post: 08-28-2010, 07:20 AM
  2. Setting environment variables for use outside program
    By guesst in forum Windows Programming
    Replies: 12
    Last Post: 09-09-2008, 12:53 PM
  3. Setting path environment variable
    By Tonto in forum Windows Programming
    Replies: 5
    Last Post: 09-01-2006, 03:03 PM
  4. Setting environment variables.
    By Ezzetabi in forum C++ Programming
    Replies: 10
    Last Post: 07-26-2005, 08:30 AM
  5. Setting OS Environment Variables
    By ImNotMad in forum C Programming
    Replies: 4
    Last Post: 10-23-2003, 02:07 AM

Tags for this Thread