Hey everyone! I'm diving into some of the new features in Bash 5.3 and I've hit a snag that has me puzzled. Check out this example:
First, I set an environment variable: `export TEST=aaabbb`.
Then I used this command:
`echo $( sed 's/a/b/g' <<< $TEST )`
And it worked perfectly, giving me `bbbbbb`.
But when I tried:
`echo ${ sed 's/a/b/g' <<< $TEST; }`
I got an error message saying `sed: couldn't flush stdout: Device not configured`.
Lastly, I tried:
`echo ${| sed 's/a/b/g' <<< $TEST; }`
And it returned `bbbbbb` without errors.
Can someone shed some light on why the second command doesn't work? Thanks!
3 Answers
It looks like the issue relates to how Bash handles pipes and output flushing. In your second command, Bash tries to close the `sed` pipe before it can complete its task. That leads to the 'Device not configured' error. Interestingly, others using macOS haven’t been able to replicate this issue. You might be encountering a race condition! Also, remember to check whether you're using the same version of Bash across different platforms. That might help clarify the discrepancies!
I haven't encountered that error, and I've tried your commands on my set up running macOS. It seems to be a portable issue since you mentioned using Homebrew. You could check your Bash configuration or even run Bash in a clean environment using `env -i /opt/homebrew/bin/bash --norc --noprofile` to diagnose further.
Thanks for the tip! I’ll check that out and see if the clean environment makes a difference.
There's a slight confusion in syntax with `${...}` and `$(...)`. Remember that `${...}` is used for variable expansion while `$(...)` is for executing commands. The behavior you're seeing with the error message suggests that Bash expected variable content but couldn't find it properly due to the usage. It may help to stick with `$(...)` for executing commands to avoid such issues.
That's really helpful advice! I’ll make sure to keep the syntax straight moving forward.
Got it, thanks! Just to confirm, is anyone else running into this on specific setups like macOS? It seems like it could be an environment-specific issue.