nushell/crates/nu-cli/src/commands/keep.rs

63 lines
1.4 KiB
Rust
Raw Normal View History

use crate::commands::WholeStreamCommand;
use crate::context::CommandRegistry;
use crate::prelude::*;
use nu_errors::ShellError;
use nu_protocol::{Signature, SyntaxShape};
use nu_source::Tagged;
pub struct Keep;
#[derive(Deserialize)]
pub struct KeepArgs {
rows: Option<Tagged<usize>>,
}
impl WholeStreamCommand for Keep {
fn name(&self) -> &str {
"keep"
}
fn signature(&self) -> Signature {
Signature::build("keep").optional(
"rows",
SyntaxShape::Int,
"starting from the front, the number of rows to keep",
)
}
fn usage(&self) -> &str {
"Keep the number of rows only"
}
fn run(
&self,
args: CommandArgs,
registry: &CommandRegistry,
) -> Result<OutputStream, ShellError> {
args.process(registry, keep)?.run()
}
fn examples(&self) -> &[Example] {
&[
Example {
description: "Keep the first row",
example: "ls | keep",
},
Example {
description: "Keep the first four rows",
example: "ls | keep 4",
},
]
}
}
fn keep(KeepArgs { rows }: KeepArgs, context: RunnableContext) -> Result<OutputStream, ShellError> {
let rows_desired = if let Some(quantity) = rows {
*quantity
} else {
1
};
Ok(OutputStream::from_input(context.input.take(rows_desired)))
}