nu_cmd_lang/core_commands/
echo.rs

1use nu_engine::command_prelude::*;
2
3#[derive(Clone)]
4pub struct Echo;
5
6impl Command for Echo {
7    fn name(&self) -> &str {
8        "echo"
9    }
10
11    fn description(&self) -> &str {
12        "Returns its arguments, ignoring the piped-in value."
13    }
14
15    fn signature(&self) -> Signature {
16        Signature::build("echo")
17            .input_output_types(vec![(Type::Nothing, Type::Any)])
18            .rest("rest", SyntaxShape::Any, "The values to echo.")
19            .category(Category::Core)
20    }
21
22    fn extra_description(&self) -> &str {
23        r#"Unlike `print`, which prints unstructured text to stdout, `echo` is like an
24identity function and simply returns its arguments. When given no arguments,
25it returns an empty string. When given one argument, it returns it as a
26nushell value. Otherwise, it returns a list of the arguments. There is usually
27little reason to use this over just writing the values as-is."#
28    }
29
30    fn run(
31        &self,
32        engine_state: &EngineState,
33        stack: &mut Stack,
34        call: &Call,
35        _input: PipelineData,
36    ) -> Result<PipelineData, ShellError> {
37        let args = call.rest(engine_state, stack, 0)?;
38        echo_impl(args, call.head)
39    }
40
41    fn run_const(
42        &self,
43        working_set: &StateWorkingSet,
44        call: &Call,
45        _input: PipelineData,
46    ) -> Result<PipelineData, ShellError> {
47        let args = call.rest_const(working_set, 0)?;
48        echo_impl(args, call.head)
49    }
50
51    fn is_const(&self) -> bool {
52        true
53    }
54
55    fn examples(&self) -> Vec<Example<'_>> {
56        vec![
57            Example {
58                description: "Put a list of numbers in the pipeline. This is the same as [1 2 3].",
59                example: "echo 1 2 3",
60                result: Some(Value::list(
61                    vec![Value::test_int(1), Value::test_int(2), Value::test_int(3)],
62                    Span::test_data(),
63                )),
64            },
65            Example {
66                description: "Returns the piped-in value, by using the special $in variable to obtain it.",
67                example: "echo $in",
68                result: None,
69            },
70        ]
71    }
72}
73
74fn echo_impl(mut args: Vec<Value>, head: Span) -> Result<PipelineData, ShellError> {
75    let value = match args.len() {
76        0 => Value::string("", head),
77        1 => args.pop().expect("one element"),
78        _ => Value::list(args, head),
79    };
80    Ok(value.into_pipeline_data())
81}
82
83#[cfg(test)]
84mod test {
85    #[test]
86    fn test_examples() {
87        use super::Echo;
88        use crate::test_examples;
89        test_examples(Echo {})
90    }
91}
nu_cmd_lang/core_commands/echo.rs

nu_cmd_lang/core_commands/
echo.rs
