How to stay in the directory after subshell completion?

Question

I'm trying to do this (just an example, not a real life situation):

$ mkdir test; ( cd test; echo "foo" > test.txt ); cat test.txt
cat: test.txt: No such file or directory

However, it fails, since cd test directory change is reverted after subshell is finished. What is a workaround? I can't use script .sh files, everything should be in one command line.

"`cd test` directory change is reverted after subshell is finished." Take it out of the subshell. — Kevin, Aug 29 '13 at 13:03
It has to be inside the subshell. I'm changing the directory in the subshell, and want to preserve this change when subshell is finished. — yegor256, Aug 29 '13 at 13:04
Then you have to change directory outside when the subshell is finished. A subshell cannot change its parent's working directory. Period. — Kevin, Aug 29 '13 at 13:05
You would probably get better and more applicable answers if you tell us the actual problem. — Kevin, Aug 29 '13 at 13:06
how about define a var in beginning, like a=test; mkdir $a; ... ; cat $a/test.txt — Jiejing Zhang, Aug 29 '13 at 13:06

score 5 · Accepted Answer · answered Aug 29 '13 at 13:32

5

Skip the subshell and use a { ... } block instead (or explain your usecase, since this example does not make so much sense):

$ find
.
$ mkdir dir; { cd dir; echo foo > test.txt; }; cat test.txt
foo
$ cd ..
$ find
.
./dir
./dir/test.txt

answered Aug 29 '13 at 13:32

Adrian Frühwirth

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Thanks, that's exactly what I'm looking for. Maybe you know the answer to this related one: http://stackoverflow.com/questions/18513631/why-pipe-resets-current-working-directory – yegor256 Aug 29 '13 at 14:25
@yegor256 Yes, as stated in the answers over there, the pipe creates a subshell. – Adrian Frühwirth Aug 29 '13 at 14:49

score 3 · Answer 2 · answered Aug 29 '13 at 13:17

Why not just?

mkdir test; echo "foo" > test/test.txt; cat test/test.txt

Another way is

mkdir test; cd "$(cd test; echo "foo" > test.txt; echo "$PWD";)"; cat test.txt

Or

mkdir test; (cd test; echo "foo" > test.txt; echo "$PWD" > /some/file); cd "$(</some/file)"; cat test.txt

score 1 · Answer 3 · answered Aug 29 '13 at 13:20

As commenters have said, a child process can't modify the parent's working directory. You can return a value from the child process for the parent to read, then make the parent act on this value. Meaningless bash example:-

$ mkdir test; DIR=$( cd test; echo "foo" > test.txt; echo test ); cat $DIR/test.txt

How to stay in the directory after subshell completion?

3 Answers3