WasiCli

1 type6 functions

Reading and writing a command-line program's standard streams, its arguments, its environment variables, and its exit, for a WASI preview1 host. The wasip2 package's WasiCli, preloaded on the component target instead, has print, args, env and exit, with exit reaching the host as success or failure only.

_start = () -> match WasiCli.readLine() {
  Ok(line) -> WasiCli.print(String.concat(line, "\n"))
  Err(EndOfInput) -> WasiCli.exit(0)
}

At a glance

Result
Shorthand for [Ok(a) | Err(e)], the variant this module's fallible functions return.
print
Writes the string to stdout, exactly as it is: no newline is added.
readAll
Everything left on stdin, read to the end of input.
readLine
The next line of stdin, without its \n or \r\n.
exit
Stop the program with code as its exit status.
args
The program's arguments, starting with the program's own path as the host gives it.
env
The value of the environment variable name, everything after the first = of its entry, or Err(NotFound) when the environment has none.

Types

Result

Result(a, e) = [Ok(a) | Err(e)]

Shorthand for [Ok(a) | Err(e)], the variant this module's fallible functions return.

Functions

print

(String) -> Unitimpure

Writes the string to stdout, exactly as it is: no newline is added.

readAll

() -> Stringimpure

Everything left on stdin, read to the end of input.

readLine

() -> Result(String, [EndOfInput | e])impure

The next line of stdin, without its \n or \r\n. An empty line is Ok(""), and a closed stdin is Err(EndOfInput), so a loop can tell the two apart. A last line with no terminator is still Ok; the end of input is reported on the call after it.

exit

(Int) -> aimpure

Stop the program with code as its exit status. It does not return, so its result is any type the call stands in for.

args

() -> List(String)impure

The program's arguments, starting with the program's own path as the host gives it.

env

(String) -> Result(String, [NotFound | e])impure

The value of the environment variable name, everything after the first = of its entry, or Err(NotFound) when the environment has none.