run and shell

Usage

rc run --stack <linguagem> (--code '<código>' | --file <arquivo>) [--stdin '<texto>'] [--timeout 5s]

Flag	Default	Description
--stack	—	catalog language
--code	—	code of the main file
--file	—	reads the code from a local file (replaces --code)
--stdin	empty	the program's standard input
--timeout	10s	duration in Go format (500ms, 5s, 2m); maximum 300 s
--gpu	off	VM with the host GPU over Vulkan (virtio-gpu/Venus); only on a stack with gpu in the catalog, otherwise E007. See GPU

What happens

run does not use the pool: it boots a fresh VM (cold boot), runs the job and destroys the VM. On the measured machine, a Python job took ~240 ms total, with 31–38 ms of execution.

Output is streamed: each chunk appears in the terminal while the program runs, not only at the end.

• The program's stdout goes to stdout.
• The program's stderr goes to stderr, followed by a summary line:

[status=success exit=0 exec=33ms total=241ms timeout=false]

(illustrative values)

Language buffering

Streaming delivers what the program writes to the pipe. When the output is not a terminal, several languages accumulate stdout in a buffer and only write it at the end (or block by block):

Language	Streaming behavior
Python	line by line: the runner sets PYTHONUNBUFFERED=1 in streaming mode
Node.js, Go, Bash, sh	line by line, no configuration
C, C++ (printf), Ruby, Perl	in blocks: call fflush(stdout), $stdout.sync = true or $| = 1 in the program
stderr	unbuffered in all of them

Exit code

Situation	rc
program exited with 0	0
program exited with a non-zero code, failed to compile or hit the timeout	1
job rejected (language, limits) or infrastructure failure	1, with the error message

Examples

# Python with stdin
rc run --stack python --code 'print(input().upper())' --stdin 'olá'

# Local file
rc run --stack go --file ./main.go

# Short timeout
rc run --stack bash --code 'sleep 10' --timeout 2s

Through the Taskfile:

task run -- --stack python --code 'print(1)'

shell

rc shell --stack python [--gpu]
task shell -- --stack python

Opens an interactive shell in a fresh VM of the stack, with the same image the jobs use: read-only root, no network and a writable /tmp. The VM disappears on exit.

• In a terminal, the guest gets a real TTY (a virtio console in place of the implicit console) and the host terminal stays in raw mode during the session: Ctrl+C interrupts only the command in the guest, and the window size reaches the guest (stty size).
• With stdin from a pipe, the console is the regular one, without a TTY: echo 'python3 -V' | rc shell --stack python works.
• It is bash if the image has it; on Alpine images, sh.

For a shell that keeps what you install, use a machine: rc machine run -it --stack python (gone at the end) or rc machine shell on a running machine. See machine.

Prerequisite

The language image must be built (rc image build --stack <l>); without it, the job is rejected with E006.