在 bash 脚本中设置环境变量

Question

I have to admit I'm very rusty with bash scripting. I want to set 2 temp env vars and then run a binary.

The command is like this:

ENV_1=firstparam ENV_2=secondparam my_binary

I want to move the 2 env var assignment in a bash script and use a command like this:

setparams.sh my_binary

setparams.sh

#!/bin/bash
ENV_1=firstparam
ENV_2=secondparam

What's wrong here? Why do the vars are not being set?

Answer 1

By default all user defined variables are local. They are not exported to new processes. Use export command to export variables and functions

export ENV_1=firstparam
export ENV_2=secondparam

Also, instead of executing you should call source (built-in command that executes the content of the file passed as argument, in the current shell):

source setparams.sh && my_binary

Answer 2

Since you're passing my_binary as an argument to the script, I assume you want the script to (a) set the environment variables and then (b) invoke the command you sent it.

One way to do that is:

#!/bin/bash

ENV_1=firstparam ENV_2=secondparam "$@"

"$@" expands to the list of arguments you passed to the script.

If you set variables like that, they'll be inherited in the environment of any command you run on the same command line , but not by any subsequent commands.

If you wanted to execute more than one command with those environment variables, you could do:

#!/bin/bash

export ENV_1=firstparam
export ENV_2=secondparam
some_command
some_other_command

Then $ENV_1 and $ENV_2 will appear in the environment of some_command and some_other_command -- but not in the environment of your shell after set_params.sh finishes.

If you want a script to set environment variables that will be available in your interactive shell, you'll have to invoke it with . ./set_params.sh . ./set_params.sh or source./set_params.sh . (And in that case you don't need the #!/bin/bash at the top, since it will execute in your current shell.)

Answer 3

You need to export your environment variables:

setparams.sh

#!/usr/bin/env bash

# Export environment variables
export ENV_1=firstparam
export ENV_2=secondparam

# Launch binary with its provided arguments
"$@"

Testing it:

./setparams.sh bash -c 'echo "$ENV_1"'

Output:

firstparam