hello everyone.

Here is an easy question.

How do I access (read and write) system variables in linux from a C program?
For example $HOSTNAME.

I've googled... searched this site but to no luck.

Thnx in advance for any help or pointers.

Sincerly Kristoffer Nordstrm

: hello everyone.
:
: Here is an easy question.
:
: How do I access (read and write) system variables in linux from a C program?
: For example $HOSTNAME.
:
: I've googled... searched this site but to no luck.
:
: Thnx in advance for any help or pointers.
:
: Sincerly Kristoffer Nordstrm
:

Not sure if this is what you want, but in <stdlib.h> there are a few environment variable functions.. setenv(), getenv(), putenv(), clearenv(), unsetenv(), and there's also "extern char **environ" (declared in <unistd.h>, or you can declare it yourself) which lets you access the environment variables as an array of strings in the form of `name=value'.


To understand recursive, first you need to understand recursive

Thnx a million.

That was exactly the functions I was looking for.
Now I will be able to pass some data between my processes.

At least I hope so... Im just worried how "global" these variables get .... but as I said thats exactly the answer I was looking for.
Thnx for the speedy reply.

Sincerly Kristoffer Nordstrm


: Not sure if this is what you want, but in <stdlib.h> there are a few
environment variable functions.. setenv(), getenv(), putenv(),
clearenv(), unsetenv(), and there's also "extern char **environ" (declared in <unistd.h>, or you can declare it yourself) which lets you access the environment variables as an array of strings in the form of `name=value'.
:
:
: To understand recursive, first you need to understand recursive
:
:

Isn't that what pipe() is used for??



: Thnx a million.
:
: That was exactly the functions I was looking for.
: Now I will be able to pass some data between my processes.
:
: At least I hope so... Im just worried how "global" these variables get .... but as I said thats exactly the answer I was looking for.
: Thnx for the speedy reply.
:
: Sincerly Kristoffer Nordstrm
:
:
: : Not sure if this is what you want, but in <stdlib.h> there are a few
: environment variable functions.. setenv(), getenv(), putenv(),
: clearenv(), unsetenv(), and there's also "extern char **environ" (declared in <unistd.h>, or you can declare it yourself) which lets you access the environment variables as an array of strings in the form of `name=value'.
: :
: :
: : To understand recursive, first you need to understand recursive
: :
: :
:
:

To understand recursive, first you need to understand recursive

I believe that pipe() has use in conjunction with fork() which my text tells me creates a duplicate process as the calling process, but with a different process id.

If you had completely different processes that you wanted to trade information between, I am not sure that you could do it using pipe().



;

: Isn't that what pipe() is used for??
:
:
:
: : Thnx a million.
: :
: : That was exactly the functions I was looking for.
: : Now I will be able to pass some data between my processes.
: :
: : At least I hope so... Im just worried how "global" these variables get .... but as I said thats exactly the answer I was looking for.
: : Thnx for the speedy reply.
: :
: : Sincerly Kristoffer Nordstrm
: :
: :
: : : Not sure if this is what you want, but in <stdlib.h> there are a few
: : environment variable functions.. setenv(), getenv(), putenv(),
: : clearenv(), unsetenv(), and there's also "extern char **environ" (declared in <unistd.h>, or you can declare it yourself) which lets you access the environment variables as an array of strings in the form of `name=value'.
: : :
: : :
: : : To understand recursive, first you need to understand recursive
: : :
: : :
: :
: :
:
: To understand recursive, first you need to understand recursive
:
:

Yea you're right. Looks like named pipes would work, but there are better ways. http://www.linuxhq.com/guides/LPG/node7.html

: I believe that pipe() has use in conjunction with fork() which my text tells me creates a duplicate process as the calling process, but with a different process id.
:
: If you had completely different processes that you wanted to trade information between, I am not sure that you could do it using pipe().
:
:
:
: ;
:
: : Isn't that what pipe() is used for??
: :
: :
: :
: : : Thnx a million.
: : :
: : : That was exactly the functions I was looking for.
: : : Now I will be able to pass some data between my processes.
: : :
: : : At least I hope so... Im just worried how "global" these variables get .... but as I said thats exactly the answer I was looking for.
: : : Thnx for the speedy reply.
: : :
: : : Sincerly Kristoffer Nordstrm
: : :
: : :
: : : : Not sure if this is what you want, but in <stdlib.h> there are a few
: : : environment variable functions.. setenv(), getenv(), putenv(),
: : : clearenv(), unsetenv(), and there's also "extern char **environ" (declared in <unistd.h>, or you can declare it yourself) which lets you access the environment variables as an array of strings in the form of `name=value'.
: : : :
: : : :
: : : : To understand recursive, first you need to understand recursive
: : : :
: : : :
: : :
: : :
: :
: : To understand recursive, first you need to understand recursive
: :
: :
:
:

To understand recursive, first you need to understand recursive

Thnx for the answers to both of you.

Teh situation I have is two entirely different processes with different memory and everything.
I will definatly look at the article mentioned previuosly .... another thought is to use /proc for this.

Anyway thnx for the time and effort.

Sincerly Kristoffer Nordstrm