Btukfyl

Use the "dot space script" calling syntax. For example, here's how to do it using the full path to a script:

. /path/to/set_env_vars.sh

And here's how to do it if you're in the same directory as the script:

. set_env_vars.sh

These execute the script under the current shell instead of loading another one (which is what would happen if you did ./set_env_vars.sh). Because it runs in the same shell, the environmental variables you set will be available when it exits.

This is the same thing as calling source set_env_vars.sh, but it's shorter to type and might work in some places where source doesn't.

You're not going to be able to modify the caller's shell because it's in a different process context. When child processes inherit your shell's variables, they're
inheriting copies themselves.

One thing you can do is to write a script that emits the correct commands for tcsh
or sh based how it's invoked. If you're script is "setit" then do:

ln -s setit setit-sh

and

ln -s setit setit-csh

Now either directly or in an alias, you do this from sh

eval `setit-sh`

or this from csh

eval `setit-csh`

setit uses $0 to determine its output style.

This is reminescent of how people use to get the TERM environment variable set.

The advantage here is that setit is just written in whichever shell you like as in:

#!/bin/bash

arg0=$0

arg0=${arg0##*/}

for nv in 

   NAME1=VALUE1 

   NAME2=VALUE2

do

   if [ x$arg0 = xsetit-sh ]; then

      echo 'export '$nv' ;'

   elif [ x$arg0 = xsetit-csh ]; then

      echo 'setenv '${nv%%=*}' '${nv##*=}' ;'

   fi

done

with the symbolic links given above, and the eval of the backquoted expression, this has the desired result.

To simplify invocation for csh, tcsh, or similar shells:

alias dosetit 'eval `setit-csh`'

or for sh, bash, and the like:

alias dosetit='eval `setit-sh`'

One nice thing about this is that you only have to maintain the list in one place.
In theory you could even stick the list in a file and put cat nvpairfilename between "in" and "do".

This is pretty much how login shell terminal settings used to be done: a script would output statments to be executed in the login shell. An alias would generally be used to make invocation simple, as in "tset vt100". As mentioned in another answer, there is also similar functionality in the INN UseNet news server.

In my .bash_profile I have :

# No Proxy

function noproxy

{

    /usr/local/sbin/noproxy  #turn off proxy server

    unset http_proxy HTTP_PROXY https_proxy HTTPs_PROXY

}





# Proxy

function setproxy

{

    sh /usr/local/sbin/proxyon  #turn on proxy server 

    http_proxy=http://127.0.0.1:8118/

    HTTP_PROXY=$http_proxy

    https_proxy=$http_proxy

    HTTPS_PROXY=$https_proxy

    export http_proxy https_proxy HTTP_PROXY HTTPS_PROXY

}

So when I want to disable the proxy,
the function(s) run in the login shell and sets the variables
as expected and wanted.

It's "kind of" possible through using gdb and setenv(3), although I have a hard time recommending actually doing this. (Additionally, i.e. the most recent ubuntu won't actually let you do this without telling the kernel to be more permissive about ptrace, and the same may go for other distros as well).

$ cat setfoo

#! /bin/bash



gdb /proc/${PPID}/exe ${PPID} <<END >/dev/null

call setenv("foo", "bar", 0)

END

$ echo $foo



$ ./setfoo

$ echo $foo

bar

This works — it isn't what I'd use, but it 'works'. Let's create a script teredo to set the environment variable TEREDO_WORMS:

#!/bin/ksh

export TEREDO_WORMS=ukelele

exec $SHELL -i

It will be interpreted by the Korn shell, exports the environment variable, and then replaces itself with a new interactive shell.

Before running this script, we have SHELL set in the environment to the C shell, and the environment variable TEREDO_WORMS is not set:

% env | grep SHELL

SHELL=/bin/csh

% env | grep TEREDO

%

When the script is run, you are in a new shell, another interactive C shell, but the environment variable is set:

% teredo

% env | grep TEREDO

TEREDO_WORMS=ukelele

%

When you exit from this shell, the original shell takes over:

% exit

% env | grep TEREDO

%

The environment variable is not set in the original shell's environment. If you use exec teredo to run the command, then the original interactive shell is replaced by the Korn shell that sets the environment, and then that in turn is replaced by a new interactive C shell:

% exec teredo

% env | grep TEREDO

TEREDO_WORMS=ukelele

%

If you type exit (or Control-D), then your shell exits, probably logging you out of that window, or taking you back to the previous level of shell from where the experiments started.

The same mechanism works for Bash or Korn shell. You may find that the prompt after the exit commands appears in funny places.

Note the discussion in the comments. This is not a solution I would recommend, but it does achieve the stated purpose of a single script to set the environment that works with all shells (that accept the -i option to make an interactive shell). You could also add "$@" after the option to relay any other arguments, which might then make the shell usable as a general 'set environment and execute command' tool. You might want to omit the -i if there are other arguments, leading to:

#!/bin/ksh

export TEREDO_WORMS=ukelele

exec $SHELL "${@-'-i'}"

The "${@-'-i'}" bit means 'if the argument list contains at least one argument, use the original argument list; otherwise, substitute -i for the non-existent arguments'.

You should use modules, see http://modules.sourceforge.net/

EDIT: The modules package has not been updated since 2012 but still works ok for the basics. All the new features, bells and whistles happen in lmod this day (which I like it more): https://www.tacc.utexas.edu/research-development/tacc-projects/lmod

Another workaround that I don't see mentioned is to write the variable value to a file.

I ran into a very similar issue where I wanted to be able to run the last set test (instead of all my tests). My first plan was to write one command for setting the env variable TESTCASE, and then have another command that would use this to run the test. Needless to say that I had the same exact issue as you did.

But then I came up with this simple hack:

First command ( testset ):

#!/bin/bash



if [ $# -eq 1 ]

then

  echo $1 > ~/.TESTCASE

  echo "TESTCASE has been set to: $1"

else

  echo "Come again?"

fi

Second command (testrun ):

#!/bin/bash



TESTCASE=$(cat ~/.TESTCASE)

drush test-run $TESTCASE

Add the -l flag in top of your bash script i.e.

#!/usr/bin/env bash -l



...



export NAME1="VALUE1"

export NAME2="VALUE2"

The values with NAME1 and NAME2 will now have been exported to your current environment, however these changes are not permanent. If you want them to be permanent you need to add them to your .bashrc file or other init file.

From the man pages:

-l Make bash act as if it had been invoked as a login shell (see INVOCATION below).

You can instruct the child process to print its environment variables (by calling "env"), then loop over the printed environment variables in the parent process and call "export" on those variables.

The following code is based on Capturing output of find . -print0 into a bash array

If the parent shell is the bash, you can use

while IFS= read -r -d $'' line; do

    export "$line"

done < <(bash -s <<< 'export VARNAME=something; env -0')

echo $VARNAME

If the parent shell is the dash, then read does not provide the -d flag and the code gets more complicated

TMPDIR=$(mktemp -d)

mkfifo $TMPDIR/fifo

(bash -s << "EOF"

    export VARNAME=something

    while IFS= read -r -d $'' line; do

        echo $(printf '%q' "$line")

    done < <(env -0)

EOF

) > $TMPDIR/fifo &

while read -r line; do export "$(eval echo $line)"; done < $TMPDIR/fifo

rm -r $TMPDIR

echo $VARNAME

You can invoke another one Bash with the different bash_profile.
Also, you can create special bash_profile for using in multi-bashprofile environment.

Remember that you can use functions inside of bashprofile, and that functions will be avialable globally.
for example, "function user { export USER_NAME $1 }" can set variable in runtime, for example: user olegchir && env | grep olegchir

Technically, that is correct -- only 'eval' doesn't fork another shell. However, from the point of view of the application you're trying to run in the modified environment, the difference is nil: the child inherits the environment of its parent, so the (modified) environment is conveyed to all descending processes.

Ipso facto, the changed environment variable 'sticks' -- as long as you are running under the parent program/shell.

If it is absolutely necessary for the environment variable to remain after the parent (Perl or shell) has exited, it is necessary for the parent shell to do the heavy lifting. One method I've seen in the documentation is for the current script to spawn an executable file with the necessary 'export' language, and then trick the parent shell into executing it -- always being cognizant of the fact that you need to preface the command with 'source' if you're trying to leave a non-volatile version of the modified environment behind. A Kluge at best.

The second method is to modify the script that initiates the shell environment (.bashrc or whatever) to contain the modified parameter. This can be dangerous -- if you hose up the initialization script it may make your shell unavailable the next time it tries to launch. There are plenty of tools for modifying the current shell; by affixing the necessary tweaks to the 'launcher' you effectively push those changes forward as well.
Generally not a good idea; if you only need the environment changes for a particular application suite, you'll have to go back and return the shell launch script to its pristine state (using vi or whatever) afterwards.

In short, there are no good (and easy) methods. Presumably this was made difficult to ensure the security of the system was not irrevocably compromised.

The short answer is no, you cannot alter the environment of the parent process, but it seems like what you want is an environment with custom environment variables and the shell that the user has chosen.

So why not simply something like

#!/usr/bin/env bash

FOO=foo $SHELL

Then when you are done with the environment, just exit.

You could always use aliases

alias your_env='source ~/scripts/your_env.sh'

Another option is to use "Environment Modules" (http://modules.sourceforge.net/). This unfortunately introduces a third language into the mix. You define the environment with the language of Tcl, but there are a few handy commands for typical modifications (prepend vs. append vs set). You will also need to have environment modules installed. You can then use module load *XXX* to name the environment you want. The module command is basically a fancy alias for the eval mechanism described above by Thomas Kammeyer. The main advantage here is that you can maintain the environment in one language and rely on "Environment Modules" to translate it to sh, ksh, bash, csh, tcsh, zsh, python (?!?!!), etc.

I did this many years ago. If I rememeber correctly, I included an alias in each of .bashrc and .cshrc, with parameters, aliasing the respective forms of setting the environment to a common form.

Then the script that you will source in any of the two shells has a command with that last form, that is suitable aliased in each shell.

If I find the concrete aliases, I will post them.

I created a solution using pipes, eval and signal.

parent() {

    if [ -z "$G_EVAL_FD" ]; then

            die 1 "Rode primeiro parent_setup no processo pai"

    fi

    if [ $(ppid) = "$$" ]; then

            "$@"

    else

            kill -SIGUSR1 $$

            echo "$@">&$G_EVAL_FD

    fi

}

parent_setup() {

    G_EVAL_FD=99

    tempfile=$(mktemp -u)

    mkfifo "$tempfile"

    eval "exec $G_EVAL_FD<>'$tempfile'"

    rm -f "$tempfile"

    trap "read CMD <&$G_EVAL_FD; eval "$CMD"" USR1

}

parent_setup #on parent shell context

( A=1 ); echo $A # prints nothing

( parent A=1 ); echo $A # prints 1

It might work with any command.

Under OS X bash you can do the following:


Create the bash script file to unset the variable

#!/bin/bash

unset http_proxy

Make the file executable

sudo chmod 744 unsetvar

Create alias

alias unsetvar='source /your/path/to/the/script/unsetvar'

It should be ready to use so long you have the folder containing your script file appended to the path.

I don't see any answer documenting how to work around this problem with cooperating processes. A common pattern with things like ssh-agent is to have the child process print an expression which the parent can eval.

bash$ eval $(shh-agent)

For example, ssh-agent has options to select Csh or Bourne-compatible output syntax.

bash$ ssh-agent

SSH2_AUTH_SOCK=/tmp/ssh-era/ssh2-10690-agent; export SSH2_AUTH_SOCK;

SSH2_AGENT_PID=10691; export SSH2_AGENT_PID;

echo Agent pid 10691;

(This causes the agent to start running, but doesn't allow you to actually use it, unless you now copy-paste this output to your shell prompt.) Compare:

bash$ ssh-agent -c

setenv SSH2_AUTH_SOCK /tmp/ssh-era/ssh2-10751-agent;

setenv SSH2_AGENT_PID 10752;

echo Agent pid 10752;

(As you can see, csh and tcsh uses setenv to set varibles.)

Your own program can do this, too.

bash$ foo=$(makefoo)

Your makefoo script would simply calculate and print the value, and let the caller do whatever they want with it -- assigning it to a variable is a common use case, but probably not something you want to hard-code into the tool which produces the value.

It's not what I would call outstanding, but this also works if you need to call the script from the shell anyway. It's not a good solution, but for a single static environment variable, it works well enough.

1.) Create a script with a condition that exits either 0 (Successful) or 1 (Not successful)

if [[ $foo == "True" ]]; then

    exit 0

else

    exit 1

2.) Create an alias that is dependent on the exit code.

alias='myscript.sh && export MyVariable'

You call the alias, which calls the script, which evaluates the condition, which is required to exit zero via the '&&' in order to set the environment variable in the parent shell.

This is flotsam, but it can be useful in a pinch.