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Bash: Capture Output of Command Run in Background


Bash: Capture output of command run in background - Stack Overflow

see efficient bash writing

The solution is the following construct

$ exec 3< <(yes) # Save stdout of the ‘yes’ job as (input) fd 3.

This opens the file as input fd 3 before the background job is started.

You can now read from the background job whenever you prefer. For a stupid example

$ for i in 1 2 3; do read <&3 line; echo “$line”; done y y y

Note that this has slightly different semantics than having the background job write to a drive backed file: the background job will be blocked when the buffer is full (you empty the buffer by reading from the fd). By contrast, writing to a drive-backed file is only blocking when the hard drive doesn’t respond