Can a shell script set environment variables of the calling shell? [duplicate]

Answer 1

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 $'\0' line; do
    export "$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 $'\0' 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

Answer 2

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.

Answer 3

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

Answer 4

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

Answer 5

Your shell process has a copy of the parent's environment and no access to the parent process's environment whatsoever. When your shell process terminates any changes you've made to its environment are lost. Sourcing a script file is the most commonly used method for configuring a shell environment, you may just want to bite the bullet and maintain one for each of the two flavors of shell.

Answer 6

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.