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nbudstee: Non-Blocking Unix Domain Socket Tee

Tees Input to zero or more non-blocking Unix domain sockets, each of which can have zero or more connected readers,
and/or to zero or more existing FIFOs, each of which can have exactly one existing reader.
Also copies to STDOUT, unless -n/--no-stdout is used.
Input defaults to STDIN

Usage:

nbudstee [options] uds1 uds2 ...

Where uds1 uds2 ... are zero or more filenames to use as Unix domain sockets, or existing FIFOs.

Options:

  • -n, --no-stdout
    Do not copy input to STDOUT.
  • -b, --unlink-before
    First try to unlink any existing sockets. This will not try to unlink non-sockets.
  • -u, --unlink-after
    Try to unlink all sockets and FIFOs when done.
  • -m, --max-queue bytes
    Maximum amount of data to buffer for each connected reader (approximate).
    Accepts suffixes: k, M, G, for kilobytes, megabytes, gigabytes (multiples of 1024).
    Default: 64k.
    Above this limit new data for that socket reader will be discarded (unless -d/--no-overflow is used).
  • -d, --no-overflow
    Disconnect readers which would otherwise have data discarded because their buffer is full.
  • -i, --input file
    Read from file instead of STDIN.
  • -I, --input-reopen file
    Read from file instead of STDIN.
    When the end of input is reached, reopen from the beginning.
    This is primarily intended for FIFOs.

Use Case:

On demand logging, in particular in shell pipelines.

... | process | nbudstee -u uds1 | process | ...
... | process 2> >(nbudstee -n -u uds2) | ...

Any number of readers can read from each socket, on demand, without blocking the main pipeline, or requiring data to be dumped to a file.
This is useful for occasional debugging/sampling, or for inserting/removing tees without interrupting the main pipeline.

A possible command to read from a Unix domain socket is:

nc -U uds1

Notes:

  • No attempt is made to line-buffer or coalesce the input. A reader could receive a partial line when connecting/disconnecting if the input source is not line-buffered.
    If required line-buffer the input before piping it to nbudstee.
  • Writes to STDOUT are blocking.

URLs:

License:

GPLv2