Shell – How to unset a variable at the command line

shellyaourt

I have tried the following command to set Proxy on yaourt:

export ALL_PROXY=http://proxy.example.com:8080

The question is how to unset the proxy on yaourt?
In general, how can I unset the value of a variable in the current shell?

Best Answer

To remove an environment variable, run

unset ALL_PROXY

Note that an environment variable only takes effect in a program and the program it launches. If you set an environment variable in one shell window, it doesn't affect other shell windows.

If you've added export ALL_PROXY=… to an initialization file, remove it from there.

You can run export with no arguments to see what environment variables are set in the current shell.

Remember that to make a shell variable available to the programs started by that shell, you need to export it, either by running export VAR after the assignment VAR=VALUE or by combining the two (export VAR=VALUE).

Related Solutions

Bash Variable Visibility in Subshell of Command Substitution

The statement:

Because of that, any variables you create in the script aren't available to the subshell command.

is false. The scope of a variable defined in the parent shell is the entire script (including subshells created with command substitution).

Running:

#!/bin/bash
var=5.5555
ans1=$(echo $var)
ans2=$(var=6; echo $var)
echo $ans1
echo $ans2

will give the result:

5.5555
6

$var is resolved by the subshell:

if no local variable is specified, the value of three global variable is used
if a local variable is specified, it uses its value

Bash – Is the export command behaviour different in sh and in bash

It seems that you detected a POSIX deviation in bash that is also a deviation from the historic Bourne Shell. You may call it a bug or a just deviating behavior.

The script you refer to prints

1
2

with all shells except bash in default behavior.

If you call bash --posix, it works correctly.

From a pointer from user Kusalananda it seems that bash by default makes all builtin commands restore their temporary environment at exit and not just for the non-special builtins. Since export is a special builtin, POSIX requires a shell to behave the same as a Bourne Shell from the early 1980s end to keep the environment value.

Since bash does not implement this by default, you get the deviation.

Best Answer

Related Solutions

Bash Variable Visibility in Subshell of Command Substitution

Bash – Is the export command behaviour different in sh and in bash

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