add term size command (#792)

* add `term-size` command

* Update term_size.rs

Co-authored-by: JT <547158+jntrnr@users.noreply.github.com>

crates/nu-command/src/default_context.rs

@@ -172,6 +172,7 @@ pub fn create_default_context(cwd: impl AsRef<Path>) -> EngineState {
             Input,
             Kill,
             Sleep,
+            TermSize,
         };
 
         // Date

crates/nu-command/src/platform/mod.rs

@@ -3,9 +3,11 @@ mod clear;
 mod input;
 mod kill;
 mod sleep;
+mod term_size;
 
 pub use ansi::{Ansi, AnsiGradient, AnsiStrip};
 pub use clear::Clear;
 pub use input::Input;
 pub use kill::Kill;
 pub use sleep::Sleep;
+pub use term_size::TermSize;

crates/nu-command/src/platform/term_size.rs

@@ -0,0 +1,113 @@
+use nu_protocol::ast::Call;
+use nu_protocol::engine::{Command, EngineState, Stack};
+use nu_protocol::{Category, Example, IntoPipelineData, PipelineData, Signature, Span, Value};
+use terminal_size::{terminal_size, Height, Width};
+
+#[derive(Clone)]
+pub struct TermSize;
+
+impl Command for TermSize {
+    fn name(&self) -> &str {
+        "term size"
+    }
+
+    fn usage(&self) -> &str {
+        "Returns the terminal size"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("term size")
+            .switch(
+                "columns",
+                "Report only the width of the terminal",
+                Some('c'),
+            )
+            .switch("rows", "Report only the height of the terminal", Some('r'))
+            .category(Category::Platform)
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![
+            Example {
+                description: "Return the width height of the terminal",
+                example: "term size",
+                result: None,
+            },
+            Example {
+                description: "Return the width (columns) of the terminal",
+                example: "term size -c",
+                result: None,
+            },
+            Example {
+                description: "Return the height (rows) of the terminal",
+                example: "term size -r",
+                result: None,
+            },
+        ]
+    }
+
+    fn run(
+        &self,
+        _engine_state: &EngineState,
+        _stack: &mut Stack,
+        call: &Call,
+        _input: PipelineData,
+    ) -> Result<nu_protocol::PipelineData, nu_protocol::ShellError> {
+        let head = call.head;
+        let wide = call.has_flag("columns");
+        let tall = call.has_flag("rows");
+
+        let (cols, rows) = match terminal_size() {
+            Some((w, h)) => (Width(w.0), Height(h.0)),
+            None => (Width(0), Height(0)),
+        };
+
+        Ok((match (wide, tall) {
+            (true, false) => Value::Record {
+                cols: vec!["columns".into()],
+                vals: vec![Value::Int {
+                    val: cols.0 as i64,
+                    span: Span::test_data(),
+                }],
+                span: head,
+            },
+            (true, true) => Value::Record {
+                cols: vec!["columns".into(), "rows".into()],
+                vals: vec![
+                    Value::Int {
+                        val: cols.0 as i64,
+                        span: Span::test_data(),
+                    },
+                    Value::Int {
+                        val: rows.0 as i64,
+                        span: Span::test_data(),
+                    },
+                ],
+                span: head,
+            },
+            (false, true) => Value::Record {
+                cols: vec!["rows".into()],
+                vals: vec![Value::Int {
+                    val: rows.0 as i64,
+                    span: Span::test_data(),
+                }],
+                span: head,
+            },
+            (false, false) => Value::Record {
+                cols: vec!["columns".into(), "rows".into()],
+                vals: vec![
+                    Value::Int {
+                        val: cols.0 as i64,
+                        span: Span::test_data(),
+                    },
+                    Value::Int {
+                        val: rows.0 as i64,
+                        span: Span::test_data(),
+                    },
+                ],
+                span: head,
+            },
+        })
+        .into_pipeline_data())
+    }
+}