linux - BASH: Global variables aren't updateable in a function only when that function is piped (simple example) -



linux - BASH: Global variables aren't updateable in a function only when that function is piped (simple example) -

this smells buggy, probably, can explain it:

the next script doesn't work, output below:

#!/bin/bash global_var="old" myfunc() { echo "func before set> $global_var" global_var="new" echo "func after set> $global_var" } myfunc | cat echo "final value> $global_var"

output:

func before set> old func after set> new final value> old

now, take off | cat , works!

#!/bin/bash global_var="old" myfunc() { echo "func before set> $global_var" global_var="new" echo "func after set> $global_var" } myfunc echo "final value> $global_var"

output:

func before set> old func after set> new final value> new

a pipe creates subshell. it's said in bash manual subshells cannot modify environment of parents. see these links:

http://www.gnu.org/software/bash/manual/bashref.html#pipelines

http://wiki.bash-hackers.org/scripting/processtree#actions_that_create_a_subshell

linux bash variables cat

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