$# set testvar to be a value
$testvar=asdf
$# demonstrate that it is set in the current shell
$echo $testvar
$# create a bash subprocess and examine the environment.
$bash -c "export | grep 'testvar'"

$bash -c 'echo $testvar'

$# export testvar and set it to the a value of foo
$export testvar=foo
$# create a bash subprocess and examine the environment.
$bash -c "export | grep 'testvar'"
declare -x testvar="foo"
$bash -c 'echo $testvar'
foo
$# mark testvar to not be exported
$export -n testvar
$bash -c "export | grep 'testvar'"

$bash -c 'echo $testvar'

您会注意到,如果没有导出,您创建的新bash进程将无法看到testvar.导出testvar时,新进程能够测试var.