IO

IO

Generated from MemCP commit c42e19eba on 27 August 2026. See Full SCM API documentation.

The IO module provides process-facing input and output facilities for Scheme programs and embedded services. It includes console output, environment access, files and streams, HTTP helpers, serialization, argument handling, and server-control functions.

IO functions are intentionally effectful. Treat filenames, URLs, environment values, request data, and generated output as trust boundaries; restrict administrative handlers and do not expose arbitrary IO primitives to untrusted users.

print

Prints values to stdout (only in IO environment)

Allowed number of parameters: 0–10000

Parameters

• value... (any): values to print (variadic)

Returns

• value (bool)

env

returns the content of a environment variable

Allowed number of parameters: 1–2

Parameters

• var (string): envvar
• default (string): default if the env is not found (optional)

Returns

• value (string)

help

Lists all functions or returns help for a specific function as a string

Allowed number of parameters: 0–1

Parameters

• topic (string): function to get help about (optional)

Returns

• value (string)

import

Imports a file .scm file into current namespace

Allowed number of parameters: 1–1

Parameters

• filename (string): filename relative to folder of source file or absolute path

Returns

• value (any)

load

Loads a file or stream and returns the string or iterates line-wise

Allowed number of parameters: 1–3

Parameters

• filenameOrStream (string|stream): filename relative to folder of source file, absolute path, or stream to read from
• linehandler (func): handler that reads each line; each line may end with delimiter (optional)
  • Parameters
    • line (string)
  • Returns
    • value (any)
• delimiter (string): delimiter to extract; if no delimiter is given, the file is read as whole and returned or passed to linehandler (optional)

Returns

• value (string|bool)

stream

Opens a file readonly as stream

Allowed number of parameters: 1–1

Parameters

• filename (string): filename relative to folder of source file or absolute path

Returns

• value (stream)

watch

Loads a file and calls the callback. Whenever the file changes on disk, the file is load again.

Allowed number of parameters: 2–2

Parameters

• filename (string): filename relative to folder of source file or absolute path
• updatehandler (func): handler that receives the file content whenever it changes
  • Parameters
    • content (string): new file content
  • Returns
    • result (any): ignored handler result

Returns

• value (bool)

serve

Opens a HTTP server at a given port

Allowed number of parameters: 2–2

Parameters

• port (number): port number for HTTP server
• handler (func): handler that processes each HTTP request
  • Parameters
    • req (any): HTTP request object
    • res (any): HTTP response object
  • Returns
    • result (any): handler result

Returns

• value (bool)

serveStatic

creates a static-file HTTP handler for use with serve

Allowed number of parameters: 1–1

Parameters

• directory (string): folder with the files to serve

Returns

• handler (func): HTTP handler that serves files from the configured directory
  • Parameters
    • req (any): HTTP request object
    • res (any): HTTP response object
  • Returns
    • result (any): handler result

mysql

Imports a file .scm file into current namespace

Allowed number of parameters: 4–4

Parameters

• port (number): port number for MySQL server
• getPassword (func): returns the password for a user, or nil to deny login
  • Parameters
    • username (string): user attempting to log in
  • Returns
    • password (string|nil): password used for authentication, or nil to deny login
• schemacallback (func): checks whether a user may access a schema
  • Parameters
    • username (string): authenticated user
    • schema (string): requested schema
  • Returns
    • allowed (bool): whether access is allowed
• handler (func): processes one SQL query in a schema
  • Parameters
    • schema (string)
    • sql (string)
    • resultrow (func): emits one result row
      • Parameters
        • row (list<any>)
          • column value (any)
      • Returns
        • result (any)
    • session (func): reads or updates request-local values
      • Parameters
        • key (any) (optional)
        • value (any) (optional)
      • Returns
        • stored value (any)
  • Returns
    • value (any)

Returns

• value (bool)

mysql_socket

Listen on a Unix domain socket for MySQL protocol

Allowed number of parameters: 4–4

Parameters

• socketpath (string): path to the Unix domain socket
• getPassword (func): returns the password for a user, or nil to deny login
  • Parameters
    • username (string): user attempting to log in
  • Returns
    • password (string|nil): password used for authentication, or nil to deny login
• schemacallback (func): checks whether a user may access a schema
  • Parameters
    • username (string): authenticated user
    • schema (string): requested schema
  • Returns
    • allowed (bool): whether access is allowed
• handler (func): processes one SQL query in a schema
  • Parameters
    • schema (string)
    • sql (string)
    • resultrow (func): emits one result row
      • Parameters
        • row (list<any>)
          • column value (any)
      • Returns
        • result (any)
    • session (func): reads or updates request-local values
      • Parameters
        • key (any) (optional)
        • value (any) (optional)
      • Returns
        • stored value (any)
  • Returns
    • value (any)

Returns

• value (bool)

password

Hashes a password with sha1 (for mysql user authentication)

Allowed number of parameters: 1–1

Parameters

• password (string): plain text password to hash

Returns

• value (string)

shutdown

Initiates a graceful shutdown of memcp after a short delay

Allowed number of parameters: 0–0

Parameters

This function has no parameters.

Returns

• value (bool)

crash

Hard process exit with no cleanup (kill -9 equivalent) for crash testing. SCM only, not exposed to SQL.

Allowed number of parameters: 0–0

Parameters

This function has no parameters.

Returns

• value (bool)

path

Joins path segments using the OS path separator and cleans the result

Allowed number of parameters: 0–10000

Parameters

• segments (string): path segments to join (variadic)

Returns

• value (string)

args

Returns command line arguments

Allowed number of parameters: 0–0

Parameters

This function has no parameters.

Returns

• value (list)

arg

Gets a command line argument value

Allowed number of parameters: 2–3

Parameters

• longname (string): long argument name (without --)
• shortname (string|any): short argument name (without -) or default value if only 2 args
• default (any): default value if argument not found (optional)

Returns

• value (any)