stdstream support

[ezrizhu]

symlinks /dev/std{in,out,err} to /proc/self/fd/{0,1,2} and cleanup after
tests included

[mgree]

Nice! Could we add one more test that actually uses these streams, rather than just testing that the devices exist?

Here's a simple test script that reads a number x from stdin and outputs 2x on stdout and 3x on stderr:

read x
echo $((x * 2))
echo $((x * 3)) >&2

We should be able to run echo 5 | try $SCRIPT and get 10 on stdout and 15 on stderr. Similarly, we should be able to run echo 5 >FILE; try $SCRIPT <FILE (NB redir is in our shell, not in try's arg) and get the same result.

[ezrizhu]

Nice! Could we add one more test that actually uses these streams, rather than just testing that the devices exist?

Here's a simple test script that reads a number x from stdin and outputs 2x on stdout and 3x on stderr:

read x
echo $((x * 2))
echo $((x * 3)) >&2

We should be able to run echo 5 | try $SCRIPT and get 10 on stdout and 15 on stderr. Similarly, we should be able to run echo 5 >FILE; try $SCRIPT <FILE (NB redir is in our shell, not in try's arg) and get the same result.

That example would also pass outside of this PR since it seems like sh does not need /dev/std{in,out,err} for those streams. @mgree

[mgree]

That example would also pass outside of this PR since it seems like sh does not need /dev/std{in,out,err} for those streams. @mgree

Oh! Good point lol. Then we should write a test that uses those devices appropriately.

[mgree]

I think this can be simpler and more precise.

[mgree]

why not test for exact output from both at once by capturing output in mktemped files?

[mgree]

One more test please... 🫣

[mgree]

No diff on try stderr due to mount noise, I assume? LGTM thanks!