Interview › Scripting (Bash, Groovy)
What is the difference between a subshell and the current shell? [Intermediate]
Answer
A subshell is a child shell process, often created with parentheses, pipelines, or command substitution. Changes made in a subshell, such as cd or variable assignments, do not affect the parent shell.
Technical explanation
Use ( commands ) when you want isolation, such as temporarily changing directories.
Use { commands; } when you want grouping in the current shell.
Pipeline behavior differs across shells; do not rely on variable changes inside a pipeline loop persisting unless you understand the shell options involved.
Hands-on example
pwd
(cd /tmp && pwd)
pwd # still original directory
count=0
printf '%s\n' a b | while read -r x; do count=$((count+1)); done
echo "count may still be $count because loop ran in subshell"
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