Scripting Ecasound Interactive Mode via Stdin

Ecasound fully supports feeding batch command scripts directly into its interactive mode using standard input (stdin). By invoking Ecasound with the interactive mode flag (-c), the engine continuously reads text-based instructions from the input stream, allowing you to automate multitrack processing, effect parameters, and routing. Using standard UNIX streams, redirection, pipes, and here-documents enables non-interactive, programmatic execution of Ecasound Control Interface (ECI) commands.

How Ecasound Handles Interactive Stdin

When launched with the -c option, Ecasound starts in interactive mode and listens for ECI commands via standard input. Rather than manually typing commands into the terminal prompt, you can pipe or redirect a pre-written text file containing sequential commands directly into the process.

Methods for Passing Batch Commands

1. Input Redirection

You can store your commands in a plain text file (commonly with a .eci extension) and pass it directly to Ecasound using shell redirection:

ecasound -c < batch_commands.eci

2. Using Standard Pipes

If commands need to be generated dynamically by another process, you can pipe standard output straight to Ecasound:

cat batch_commands.eci | ecasound -c

Or generate single, sequential commands inline:

printf "cs-add play_chain\nai-add input.wav\nao-add /dev/dsp\nstart\nsleep 5\nstop\nquit\n" | ecasound -c

3. Bash Here-Documents

For standalone shell scripts, embedding commands directly within a here-document avoids the need for external .eci files:

ecasound -c <<EOF
cs-add session1
c-add chain1
ai-add audio_track.wav
ao-add alsa
start
int-cmd-sleep 10
stop
quit
EOF

Essential Scripting Guidelines

• Terminating the Process: Always ensure the batch script ends with the quit command. Because stdin is redirected, failing to issue quit or close the stream may leave the process hanging or terminate abruptly without flushing audio buffers.
• Managing Playback Duration: Since Ecasound processes batch inputs sequentially at machine speed, playback commands like start need time to execute before receiving stop or quit. Use Ecasound's built-in timing commands—such as sleep <seconds> or int-cmd-sleep <seconds>—to allow playback or recording to run for the desired length of time.
• Error Handling: Ecasound interactive mode will attempt to continue parsing input even if an invalid command is encountered. Ensure command sequences are validated beforehand to prevent unintended routing or incomplete audio rendering.