How to access shell variables in C program

navin_karnam · 07-17-2007, 01:05 AM

Hi all,

How can i access the Shell variable(PATH) in c program.

Actually i am running a command in C program using "system", which will update the shell variable "COUNT" continuously. I need to access the COUNT after every second in a c program.

Thanks and Regards,
Naveen.

nc3b · 07-17-2007, 02:27 AM

Hello. Use getenv to get a specific variable, eg

Code:

char *mypath=getenv("PATH")

or use the special variable environ,

Code:

extern char **environ

which contains all environment variables.

Edit
equally, to set a variable you would use setenv

jlliagre · 07-17-2007, 02:37 AM

Quote:

Originally Posted by navin_karnam

Actually i am running a command in C program using "system", which will update the shell variable "COUNT" continuously.

If I understand correctly what you are doing, this isn't going to work.
The COUNT variable you are modifying with system is local to the system subshell, and unreachable from anything else.

navin_karnam · 07-18-2007, 12:10 AM

Thank you for the replies ..

I came to know how i can access the environment variables in c program..
But it is not solved my main problem still .. I will explain my problem clearly.

1) I have to display the progress of the command "tar zxf largesize.tgz"
2) To uncompress it is taking more than 10 min.
3) The above things i have to do in a c program and i have to display the progress of uncompressing.

4) To do the above I tried running the process in background using :
system ( " tar zxf largesize.tgz > temp & " );

But i dont know how i can check the progress of the background process.

Please help me out in solving this problem, or guide me is there any other good procedure which suits my requirement..

Thanks and Regards,
Naveen.

cfaj · 07-18-2007, 12:40 AM

Quote:

Originally Posted by navin_karnam

Thank you for the replies ..

I came to know how i can access the environment variables in c program..
But it is not solved my main problem still .. I will explain my problem clearly.

1) I have to display the progress of the command "tar zxf largesize.tgz"
2) To uncompress it is taking more than 10 min.
3) The above things i have to do in a c program and i have to display the progress of uncompressing.

4) To do the above I tried running the process in background using :
system ( " tar zxf largesize.tgz > temp & " );

But i dont know how i can check the progress of the background process.

Please help me out in solving this problem, or guide me is there any other good procedure which suits my requirement..

Use popen() instead of system(), and read the output of your command (perhaps use tar xvzf).