How to make the output (stdout, stderr) of any shell command unbuffered?

Question content

Is there a way to run a shell command without output buffering?

For example, hexdump file | ./my_script will only pass the input from hexdump to my_script in buffered chunks, not line by line.

What is the general solution to make the output of any command unbuffered?

Correct answer

As far as I know, you can't do this without ugly hacks. Writing to a pipe (or reading from a pipe) automatically turns on full buffering, there's nothing you can do about it :-(. "Line buffering" (which is what you want) is only used when reading/writing to the terminal. Ugly hack Exactly what this does: they connect the program to a pseudo-terminal so that other tools in the pipeline read/write from that terminal in line-buffered mode. The entire problem is described as follows:

• https://www.php.cn/link/01a416a7e28d0d2293e95ef842b9e773

The page also provides some suggestions (the "ugly hack" mentioned earlier), i.e. using unbuffer or doing some tricks with LD_PRELOAD.

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