How to set environment variables in fish shell - shell

Can someone please tell me what's the correct way to set a bunch of environment variables in the fish shell?
In my ~/.config/fish/config.fish file, I have a function to setup my environment variables like so:
function setTESTENV
set -x BROKER_IP '10.14.16.216'
set -x USERNAME 'foo'
set -x USERPASS 'bar'
end
When I type from the command prompt setTESTENV and do a env in the command line, I don't see this information.

Use Universal Variables.
If the variable has to be shared between all the current user Fish instances on the current computer and preserved across restarts of the shell you can set them using -U or --universal. For example:
set -Ux FOO bar
Using set with -g or --global doesn't set the variable persistently between shell instances.
Note:
Do not append to universal variables in config.fish file, because these variables will then get longer with each new shell instance. Instead, simply run set -Ux once at the command line.
Universal variables will be stored in the file ~/.config/fish/fish_variables as of Fish 3.0. In prior releases, it was ~/.config/fish/fishd.MACHINE_ID, where MACHINE_ID was typically the MAC address.

The variables you are declaring are keep in a local scope inside your function.
Use:
set -g -x
Here "g" is for global.

another option is to run:
export (cat env_file.txt |xargs -L 1)
where env_file.txt contains rows of the format VAR=VALUE
this has the benefit of keeping the variables in a format supported by other shells and tools

Environment Variables in Fish
I would like to add that, while #JosEduSol's answer is not incorrect and does help solve the OP problem, -g is only setting the scope to be global, while -x is causing the specified environment variable to be exported to child processes.
The reason the above fails, is because #cfpete is setting the env vars inside a function and the default scope will be local to that function.

Related

Can't get environment variable from /etc/profile in GoLang

I've set some environment variables in /etc/profile, I can access them from bash, but for some reason I cant get them from Go.
/etc/profile:
...
TEST_ENV=test_me
I can access it from bash:
echo $TEST_ENV
test_me
I can't access this variable from GO
os.Getenv("TEST_ENV") // returns ""
If I list the available environment variables with
os.Environ()
I don't see the variable I'm looking for, but there a few variables that might help:
SHELL=/bin/sh
USER=root
LOGNAME=root
I guess my problem is related to different sessions and shells, so I even tried running
exec.Command("source /etc/profile")
and get the variables after, but it still returns nothing.
Can you give me some tips how to get environment variables if they're set in /etc/profile? I'd prefer getting them from that file, but if necessary, I can put the variables in a different place as well.
When you set an environment variable in bash, by default it isn't exported. Only exported environment variables are passed along to processes created by the shell (i.e., programs that you run). Try export TEST_ENV=test_me.

How to set environment variables with a forward slash in the key

Is there a way to export an environment variable with a slash in the name such as:
export /myapp/db/username=someval
This post indicates it should be possible but I cannot figure out valid syntax to do so.
For background:
I am using confd to produce config files from a template and key store. The typical stores (consul, etcd) use hierarchical keys such as /myapp/db/username. I would like to transparently allow for switching between using an environment variable based provider and a configuration store that leverages hierarchical keys.
export only marks valid shell identifiers to be exported into the environment, not any string that could form a valid name/value pair in the environment. You can use env to create a new shell instance with such an environment, though.
env "/myapp/db/username=someval" bash
Yes, you can export such an environment variable but not from a bash export statement.
While bash will refuse to create an environment variable named, for example, a/b, we can create it with python and subshells created by python will see it.
As an example, consider the following python command:
$ python -c 'import os; os.environ["a/b"]="2"; os.system("/bin/bash");'
If we run this command, we are put into a subshell. From that subshell, we can see that the creation of the environment variable was successful:
$ printenv | grep a/b
a/b=2
(At this point, one may want to exit the subshell (type exit or ctrl-D) to return to the python program which will exit and return us to the main shell.)

env command does not list SHELL environmental variable

Below is the output of the env command:
[root#machine123 /etc/profile.d] env | grep SHELL
As you can see the output of env does not list the SHELL environment variable.
But when I print $SHELL, it is there:
[root#machine123 /etc/profile.d] echo $SHELL
/bin/bash
What is going on, why is SHELL missing from the env output?
If you want to know your local variables use the set command:
set lets you change or display the names and values of all shell variables and functions
Try set | grep SHELL
env or printenv displays global (or environment) variables, set local ones (which include the environment variables):
http://tldp.org/LDP/Bash-Beginners-Guide/html/sect_03_02.html
If the shell you are running does not export this variable, it will not be visible to subprocesses, including env.
Expecting it to exist and to be set to a useful value (outside of a shell script) is probably not portable. A sane (at least on POSIX) default is to assume SHELL=/bin/sh if it is unset.

What is the meaning of "export" in Bash? [duplicate]

This question already has answers here:
What does the 'export' command do?
(3 answers)
Closed 7 years ago.
When I customize my environment, I add PATH=$PATH:$My-own-Path in file .bash_profile.
The tutorials tell me I should use this one: export PATH=$PATH:$My-own-Path
So, what is the difference?
To answer your exact specific question, in this particular case, there isn't any difference. Why?
Somewhere in the initialization process, the variable PATH has already been exported. A change in the variable's value which is already exported does not need another export; this is automatic. The processes fired hereafter will get the new value.
export makes the environment variable available to child processes
From man bash:
... The export and declare -x commands allow parameters and functions to be added to and deleted from the environment. If the value of a parameter in the environment is modified, the new value becomes part of the environment, replacing the old.
Also from man bash:
export [-fn] [name[=word]] ...
export -p
The supplied names are marked for automatic export to the environment of subsequently executed commands. If the -f option is given, the names refer to functions. If no names are given, or if the -p option is supplied, a list of names of all exported variables is printed. The -n option causes the export property to be removed from each name. If a variable name is followed by =word, the value of the variable is set to word. export returns an exit status of 0 unless an invalid option is encountered, one of the names is not a valid shell variable name, or -f is supplied with a name that is not a function.
Exported variables are available to other programs. Non-exported variables are not.
Example:
$ myVar=Foo # Create local
$ env | grep '^myVar='
$ export myVar # Export myVar to child process
$ env | grep '^myVar='
Foo
If you want to read more about this, check out export (GNU Bash manual).
Also, please note that non-exported variables will be available to subshells run with (...) and other similar notations:
$ thereVar=Bar
$ (echo $thereVar; echo $myVar; $myVar=testing; echo $myVar)
Bar
Foo
Testing
$echo $myVar
Foo
The subshell cannot affect variables in the parent shell.
For more information on subshells, please reference:
Command Grouping
Command Execution Environment
Every process has an area of memory called the environment block. In the environment block are environment variables. These look like ordinary variables, for example x=42.
In most shells (C shell is an exception) you move an ordinary variable into the environment block using export. That command can also create an environment variable without going through an intermediate stage. If the variable is already in the environment block then export will have no effect.
So why? When a new process is created, the default action is to copy various "core information" from parent to child. These include the current directory, the umask, the file descriptor table, the uid and gid, and the environment block.
Note that the child only gets a copy of the parent's environment block. The variable is not shared and cannot be passed back to the parent (except by using some other inter-process communication mechanism).
You can override this default behaviour using the env program, but this is rarely required.
So, if we set an environment variable in a shell script using export then all our child processes we create, when we call other programs, will get a copy of them. Some variable names are well-known and have a special meaning, and the PATH environment variable is probably the most important of those.
The PATH environment variable is used to find programs on UNIX/Linux. Directories in PATH are searched in left-right order each time we need to load a program. Bash also caches executable paths in a hash (KornShell calls them "tracked aliases").

What does the 'export' command do?

I happen to run some commands blindly, in order to get things done.
I started to work with Jenkins recently, and then I had to use this export command to run the Jenkins WAR archive. What does the export command do in general, and why do we need to run this command, while running Jenkins (after the Jenkins home is set)?
export in sh and related shells (such as Bash), marks an environment variable to be exported to child-processes, so that the child inherits them.
export is defined in POSIX:
The shell shall give the export attribute to the variables corresponding to the specified names, which shall cause them to be in the environment of subsequently executed commands. If the name of a variable is followed by = word, then the value of that variable shall be set to word.
I guess you're coming from a Windows background. So I'll contrast them (I'm kind of new to Linux too). I found a user's reply to my comment, to be useful in figuring things out.
In Windows, a variable can be permanent or not. The term environment variable includes a variable set in the cmd shell with the SET command, as well as when the variable is set within the Windows GUI, thus set in the registry, and becoming viewable in new cmd windows.
E.g., the documentation for the set command in Windows "Displays, sets, or removes environment variables. Used without parameters, set displays the current environment settings."
In Linux, set does not display environment variables. It displays shell variables which it doesn't call/refer to as environment variables. Also, Linux doesn't use set to set variables (apart from positional parameters and shell options, which I explain as a note at the end), only to display them and even then only to display shell variables. Windows uses set for setting and displaying, e.g., set a=5, but Linux doesn't.
In Linux, I guess you could make a script that sets variables on bootup, e.g., /etc/profile or /etc/.bashrc, but otherwise, they're not permanent. They're stored in RAM.
There is a distinction in Linux between shell variables, and environment variables. In Linux, shell variables are only in the current shell, and environment variables, are in that shell and all child shells.
You can view shell variables with the set command (though note that, unlike Windows, variables are not set in Linux with the set command).
set -o posix; set (doing that set -o posix once first, helps not display too much unnecessary stuff). So set displays shell variables.
You can view environment variables with the env command.
Shell variables are set with, e.g., just a = 5.
Environment variables are set with export. Export also sets the shell variable.
Here you see shell variable zzz set with zzz = 5, and see it shows when running set, but it doesn't show as an environment variable.
Here we see yyy set with export, so it's an environment variable. And see it shows under both shell variables and environment variables:
$ zzz=5
$ set | grep zzz
zzz=5
$ env | grep zzz
$ export yyy=5
$ set | grep yyy
yyy=5
$ env | grep yyy
yyy=5
$
Other useful QnAs:
https://unix.stackexchange.com/questions/176001/how-can-i-list-all-shell-variables
https://askubuntu.com/questions/26318/environment-variable-vs-shell-variable-whats-the-difference
Note: One point which elaborates a bit and is somewhat corrective to what I've written, is that, in Linux bash, 'set' can be used to set "positional parameters" and "shell options/attributes", and technically both of those are variables, though the man pages might not describe them as such.
But still, as mentioned, set won't set shell variables or environment variables). If you do set asdf then it sets $1 to asdf, and if you do echo $1 you see asdf.
If you do set a=5 it won't set the variable a, equal to 5. It will set the positional parameter $1 equal to the string of "a=5". So if you ever saw set a=5 in Linux it's probably a mistake unless somebody actually wanted that string a=5, in $1.
The other thing that Linux's set can set, is shell options/attributes. If you do set -o you see a list of them. And you can do for example set -o verbose, off, to turn verbose on (by the way, the default happens to be off, but that makes no difference to this). Or you can do set +o verbose to turn verbose off. Windows has no such usage for its set command.
In simple terms, environment variables are set when you open a new shell session. At any time if you change any of the variable values, the shell has no way of picking that change. That means the changes you made become effective in new shell sessions.
The export command, on the other hand, provides the ability to update the current shell session about the change you made to the exported variable. You don't have to wait until new shell session to use the value of the variable you changed.

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