use crate::prelude::*; use nu_engine::WholeStreamCommand; use nu_errors::ShellError; use nu_protocol::{Signature, SyntaxShape, UntaggedValue}; pub struct Last; impl WholeStreamCommand for Last { fn name(&self) -> &str { "last" } fn signature(&self) -> Signature { Signature::build("last").optional( "rows", SyntaxShape::Number, "starting from the back, the number of rows to return", ) } fn usage(&self) -> &str { "Show only the last number of rows." } fn run(&self, args: CommandArgs) -> Result { last(args) } fn examples(&self) -> Vec { vec![ Example { description: "Get the last row", example: "echo [1 2 3] | last", result: Some(vec![UntaggedValue::int(3).into()]), }, Example { description: "Get the last three rows", example: "echo [1 2 3 4 5] | last 3", result: Some(vec![ UntaggedValue::int(3).into(), UntaggedValue::int(4).into(), UntaggedValue::int(5).into(), ]), }, ] } } fn last(args: CommandArgs) -> Result { let args = args.evaluate_once()?; let rows = args.nth(0).cloned(); let v: Vec<_> = args.input.into_vec(); let end_rows_desired = if let Some(quantity) = rows { quantity.as_usize()? } else { 1 }; let beginning_rows_to_skip = if end_rows_desired < v.len() { v.len() - end_rows_desired } else { 0 }; let iter = v.into_iter().skip(beginning_rows_to_skip); Ok(OutputStream::from_stream(iter)) } #[cfg(test)] mod tests { use super::Last; use super::ShellError; #[test] fn examples_work_as_expected() -> Result<(), ShellError> { use crate::examples::test as test_examples; test_examples(Last {}) } }