FIFO Command Input¶

milk-cli supports command FIFO (named pipe) input, allowing external processes to inject commands into a running CLI session. This enables powerful automation workflows where shell pipelines feed commands into milk-cli in real time.

Quick Start¶

milk> fifo create
[fifo] opened: /milk/shm/.milk.fifo.12345 (fd=4)

milk> echo $MCLIFIFO
/milk/shm/.milk.fifo.12345

From another terminal:

echo "mem.listim" > /milk/shm/.milk.fifo.12345

The milk-cli session shows ingestion feedback:

[fifo] ← "mem.listim"
... (command output) ...
[fifo] ✓ (0.003s)

The `fifo` Command¶

Sub-command	Description
`fifo create [path]`	Create and open a new FIFO. Auto-generates path if omitted.
`fifo open <path>`	Connect to an existing FIFO at the given path.
`fifo close`	Close and remove the current FIFO.
`fifo on`	Re-enable FIFO input (after `fifo off`).
`fifo off`	Temporarily disable FIFO input without destroying the pipe.
`fifo status`	Print current FIFO state, path, and file descriptor.
`fifo`	Same as `fifo status`.

The `$MCLIFIFO` Variable¶

The special variable $MCLIFIFO expands to the current FIFO path when a FIFO is active, or an empty string when no FIFO is open. This makes it easy to reference the FIFO in shell commands:

milk> fifo create
milk> !echo "echo hello" > $MCLIFIFO

Startup Flags¶

FIFOs can also be enabled at startup:

Flag	Description
`-f`	Auto-create a FIFO (path based on process name and PID)
`-F <path>`	Create a FIFO at the specified path

These are equivalent to running fifo create or fifo create <path> immediately after startup.

Examples¶

Batch Command Injection¶

Feed a list of commands from a file into a running milk-cli session:

# Terminal 1: start milk-cli with FIFO
milk-cli -f

# Terminal 2: send commands
cat commands.milk > $(cat /milk/shm/.milk.fifo.*)

Dynamic Processing with awk¶

Process a list of images and save specific ones based on metadata:

milk> fifo create
milk> !awk '{if ($4>200) print "iofits.saveFITS " $2 " " $2 "_save.fits"}' imlist.txt > $MCLIFIFO

Each generated command appears with ingestion feedback:

[fifo] ← "iofits.saveFITS im003 im003_save.fits"
[fifo] ✓ (0.012s)
[fifo] ← "iofits.saveFITS im007 im007_save.fits"
[fifo] ✓ (0.015s)

Pausing and Resuming FIFO Input¶

Temporarily disable FIFO input while doing interactive work, then re-enable it:

milk> fifo create
milk> fifo off
[fifo] input disabled

milk> # ... do interactive work ...

milk> fifo on
[fifo] input enabled

Connecting to Another Session's FIFO¶

If another milk-cli session has a FIFO open, you can connect to it:

milk> fifo open /milk/shm/.othersession.fifo.54321
[fifo] opened: /milk/shm/.othersession.fifo.54321 (fd=4)

Using with xargs¶

Combine find, xargs, and FIFO to batch-process files:

milk> fifo create
milk> !find /data/frames -name "*.fits" | xargs -I {} echo "iofits.loadfits {} frame" > $MCLIFIFO

Scripted FIFO Workflow¶

Create a shell script that starts milk-cli and feeds commands through the FIFO:

#!/bin/bash
# Start milk-cli with FIFO in the background
milk-cli -f &
MILKPID=$!
sleep 1

# Find the FIFO path
FIFO=$(ls /milk/shm/.milk.fifo.${MILKPID})

# Send commands
echo "mem.mk2Dim im1 128 128" > "$FIFO"
echo "mem.mk2Dim im2 256 256" > "$FIFO"
echo "mem.listim" > "$FIFO"
echo "exit" > "$FIFO"

wait $MILKPID