Passing the environment variables to the launched process bash script

Question

Under linux, I have a bash script, that launches a c++ program binary. What I need to do is set an environment variable in that script, and access that variable inside the launched C++ program using getenv .

Here is the code for the script

#!/bin/bash
export SAMPLE_VAR=1
./c++_binary

The c++ program:

char * env_var = getenv("SAMPLE_VAR");
if (env_var != NULL) printf("var set\n");

However this does not seem to work. From what I understand is that when we execute the script, it will run in a new subshell and set the environment variable SAMPLE_BAR there, but the C++ binary is launched in the same subshell as well (may be I am wrong here) so it should have access to the SAMPLE_VAR. I even tried writing a separate script that just sets the env variable, and in the main script I called that script as source env_var_set.sh to no avail.

Is it possible to pass on a newly set environment variable to a program this way ? Thanks

Did you mean `char * env_var = getenv("SAMPLE_VAR")`? Extra quotes can make all the difference. — mvp, Jun 11 '13 at 09:02
Have you tried `int main(int argc, char **argv, char **envp);` also? The `envp` should capture environment varibales as well. — user2052561, Jun 11 '13 at 09:04
this is weird - you are doing it correctly, and it should just work. About the only reason why it would not if you have some security software at work, something like [AppArmor](http://stackoverflow.com/questions/5835664/how-does-apparmor-do-environment-scrubbing). — mvp, Jun 11 '13 at 09:11
When you say "it doesn't work", is `getenv` returning `NULL`? — chepner, Jun 11 '13 at 09:37
Yes it returns NULL, i did a system("printenv") inside the program as well. And the SAMPE_VAR isnt set in the environment of the program. — Abdullah, Jun 11 '13 at 09:43
Your question mentions SAMPLE_VAR and SAMPLE_BAR; your last comment mentions SAMPE_VAR. You have to get your spelling consistent. Your code should work fine. Your script could use: `SAMPLE_VAR=1 ./c++_binary` too, which exports the variable only to the one program. — Jonathan Leffler, Jun 11 '13 at 12:46
Ah Sorry for the Typos, And my mistake, Inside the script I was launching the binary with 'sudo' which ran it in root's env and didnt have the variable set there. Removed sudo and it worked fine. Sorry for the confusion. Cheers. — Abdullah, Jun 11 '13 at 17:14

score 1 · Answer 1 · edited Jun 20 '20 at 09:12

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Since feature requests to mark a comment as an answer remain declined, I copy the above solution here.

Ah Sorry for the Typos, And my mistake, Inside the script I was launching the binary with 'sudo' which ran it in root's env and didnt have the variable set there. Removed sudo and it worked fine. Sorry for the confusion. Cheers. – Abdullah

edited Jun 20 '20 at 09:12

Community

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answered Oct 30 '13 at 13:50

Armali

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score -1 · Answer 2 · answered Jun 11 '13 at 09:05

-1

First of all you need to source your shell script in order for the env variable to be set. and secondly include quotes in the getenv call.

char * env_var = getenv("SAMPLE_VAR");
if (env_var != NULL) printf("var set\n");

answered Jun 11 '13 at 09:05

DevZer0

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He's exporting the variable and starting the binary from the same script. Sourcing versus executing the script won't make any difference. – chepner Jun 11 '13 at 09:36

Passing the environment variables to the launched process bash script

2 Answers2