WasiCli

1 type6 functions

The component target's command line: printing, reading stdin, arguments, environment variables and exiting over the WASI 0.2 CLI interfaces. The wasip1 package's WasiCli has the same names and types for all of these, so a program builds for either target. exit differs: this one reports only success or failure to the host, since wasi:cli/exit carries no other code. readLine reads a byte at a time, so that it consumes exactly the bytes it returns and a later read still sees the rest.

At a glance

Result
Shorthand for [Ok(a) | Err(e)], the variant this module's fallible functions return.
print
Write text to stdout as it is, with no newline added.
readAll
Stdin to the end of input.
readLine
One line of stdin, its terminator (\n, or \r\n) stripped.
args
The program's arguments, its own name first.
env
The value of the environment variable name, or Err(NotFound) when the environment has none.
exit
Stop the program: 0 is success and any other code is failure.

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

Write text to stdout as it is, with no newline added. A stream that fails or closes drops the rest of the text, as WasiCli.print drops a failed write.

readAll

() -> Stringimpure

Stdin to the end of input. Bytes that are not UTF-8 are replaced by U+FFFD, and a stream that fails ends the input where it stood.

readLine

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

One line of stdin, its terminator (\n, or \r\n) stripped. An empty line is Ok(""), distinct from the Err(EndOfInput) a closed stdin gives, and a last line with no terminator is still Ok. It consumes exactly the bytes it returns, so a later readAll sees the rest.

args

() -> List(String)impure

The program's arguments, its own name first.

env

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

The value of the environment variable name, or Err(NotFound) when the environment has none.

exit

(Int) -> aimpure

Stop the program: 0 is success and any other code is failure. Stable WASI 0.2.3 reports only which of the two it was, so the host's exit status is 0 or 1 whatever the nonzero code. Its exit-with-code is unstable, behind a feature hosts leave off by default (-S cli-exit-with-code in wasmtime).