nu_command/filters/
length.rs

1use std::io::Read;
2
3use nu_engine::command_prelude::*;
4
5#[derive(Clone)]
6pub struct Length;
7
8impl Command for Length {
9    fn name(&self) -> &str {
10        "length"
11    }
12
13    fn description(&self) -> &str {
14        "Count the number of items in an input list, rows in a table, or bytes in binary data."
15    }
16
17    fn signature(&self) -> nu_protocol::Signature {
18        Signature::build("length")
19            .input_output_types(vec![
20                (Type::List(Box::new(Type::Any)), Type::Int),
21                (Type::Binary, Type::Int),
22                (Type::Nothing, Type::Int),
23            ])
24            .category(Category::Filters)
25    }
26
27    fn search_terms(&self) -> Vec<&str> {
28        vec!["count", "size", "wc"]
29    }
30
31    fn run(
32        &self,
33        _engine_state: &EngineState,
34        _stack: &mut Stack,
35        call: &Call,
36        input: PipelineData,
37    ) -> Result<PipelineData, ShellError> {
38        length_row(call, input)
39    }
40
41    fn examples(&self) -> Vec<Example<'_>> {
42        vec![
43            Example {
44                description: "Count the number of items in a list",
45                example: "[1 2 3 4 5] | length",
46                result: Some(Value::test_int(5)),
47            },
48            Example {
49                description: "Count the number of rows in a table",
50                example: "[{a:1 b:2}, {a:2 b:3}] | length",
51                result: Some(Value::test_int(2)),
52            },
53            Example {
54                description: "Count the number of bytes in binary data",
55                example: "0x[01 02] | length",
56                result: Some(Value::test_int(2)),
57            },
58            Example {
59                description: "Count the length a null value",
60                example: "null | length",
61                result: Some(Value::test_int(0)),
62            },
63        ]
64    }
65}
66
67fn length_row(call: &Call, input: PipelineData) -> Result<PipelineData, ShellError> {
68    let span = input.span().unwrap_or(call.head);
69    match input {
70        PipelineData::Empty | PipelineData::Value(Value::Nothing { .. }, ..) => {
71            Ok(Value::int(0, call.head).into_pipeline_data())
72        }
73        PipelineData::Value(Value::Binary { val, .. }, ..) => {
74            Ok(Value::int(val.len() as i64, call.head).into_pipeline_data())
75        }
76        PipelineData::Value(Value::List { vals, .. }, ..) => {
77            Ok(Value::int(vals.len() as i64, call.head).into_pipeline_data())
78        }
79        PipelineData::ListStream(stream, ..) => {
80            Ok(Value::int(stream.into_iter().count() as i64, call.head).into_pipeline_data())
81        }
82        PipelineData::ByteStream(stream, ..) if stream.type_().is_binary_coercible() => {
83            Ok(Value::int(
84                match stream.reader() {
85                    Some(r) => r.bytes().count() as i64,
86                    None => 0,
87                },
88                call.head,
89            )
90            .into_pipeline_data())
91        }
92        _ => Err(ShellError::OnlySupportsThisInputType {
93            exp_input_type: "list, table, binary, and nothing".into(),
94            wrong_type: input.get_type().to_string(),
95            dst_span: call.head,
96            src_span: span,
97        }),
98    }
99}
100
101#[cfg(test)]
102mod test {
103    use super::*;
104
105    #[test]
106    fn test_examples() {
107        use crate::test_examples;
108
109        test_examples(Length {})
110    }
111}
nu_command/filters/length.rs

nu_command/filters/
length.rs
