Why can’t the bash script export variables

bashenvironment-variables

I am using MSYS and have a file vars.txt with variable, value keys like:

WINDIR C:/WINDOWS
STS_BUILD_DIRECTORY D:/STS/TMP
ALLUSERSPROFILE C:/Documents and Settings/All Users

I want to read this in and set environment variables up. I have a bash script setenv:

while read var value;
do
  echo "performing export $var=$value"
  export $var='$value'
done

and I call it with

cat vars.txt | source setenv

However in my environment the variables are not set. I also tried making it into a function but no joy. Anybody here know what I'm doign wrong? Thanks.

Best Answer

The pipe sets up a subshell. When the subshell exits, the variables are lost.

Try this:

source setenv < vars.txt

Also your single quotes may prevent the expansion of the variable (I don't know if this is true in MSYS). Try changing the export line to this:

export $var="$value"

You can use declare instead of export if the variables don't need to be exported.

Related Solutions

Bash Environment Variables – How to Export Back to Parent Process

Can't be done. The only reliable way to pass anything to the parent process is to echo it and have the parent process capture it with command substitution.

VAR=$(./myprogram)

Linux – the scope of “exported” in Unix shell variables

OK, for starters, I think you mean ps --pid and not ps ---pid.
You don't need to echo $$ and then type the number into ps --pid number; it's good enough to type ps --pid $$. Unless you're talking about
```
# echo $$
42
# su joe
% ps --pid 42
```
in which case you're doing the right thing.
What were you expecting?
--pid pidlist
-p pidlist
So, when you do ps --pid PID_of_shell, you're getting the line of ps's output for the shell process only. You might find ps -l | grep PID_of_shell more useful; it will show any line that contains PID_of_shell anywhere, including in the PPID column. I.e., it will show child processes of the shell. But, of course, grep 42 will find things like 7428.
Your guess is right; environment variables are passed from parent to child. As indicated above, your su shell is a child of your login shell (or other parent shell). Note, however, that a process can change its environment; sudo is somewhat notorious for doing this, and su does it too (e.g., it changes $USER, $LOGNAME, and $HOME unless you specify --preserve-environment, and even more if you do specify --login). Also, a process can pass its children a different environment than the one it is using; the shell does that when you say something like PAGER=cat man man_page_topic. References: 1, 2.
So, no, if you set (export) an environment variable in the shell in one terminal, and then start another terminal through the window manager, it will not see the environment variable, because it is not a child (or descendent) of the shell that set it. But, if you start a new terminal window from the shell (e.g., by xterm&), then that terminal window will inherit the shell's environment.

Best Answer

Related Solutions

Bash Environment Variables – How to Export Back to Parent Process

Linux – the scope of “exported” in Unix shell variables

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