Reading global environment variables

Question

I have a process which is created by execve() from another program and a specific set of environment is passed to it. However, I would need to read a global environment variable that may or may not be set by the user based on certain aspects. For example, $PATH is set when the execve() is called, but if the user stes $LOWMEM=1 ( export LOWMEM=1 ) before the program is exec'ed, then the program will not make malloc() calls larger than 1KB .

when I do a getenv("LOWMEM") call from the program it returns NULL where as I have added LOWMEM=1 in /etc/enviroment and echo $LOWMWM shows the value as 1. But I don't see LOWMEM entry in /proc/<PID>/environ . Whereas I had rebooted the system after adding the entry to the /etc/environment .

Is it not possible to read global environment from a process running under specific environment without explicitly passing it from the parent process?

Answer 1

It seems most likely that you're clearing out the entry for LOWMEM while using execve . Instead, it might be better to call setenv for the new variables you want, either in the parent or in the child and then call execv .