feature: add check for whether the output is to a terminal (#760)

Adds a warning if the user is calling bottom from an environment where the output is not a terminal.

CHANGELOG.md

@@ -12,7 +12,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - [#711](https://github.com/ClementTsang/bottom/pull/711): Fix building in Rust beta 1.61 due to `as_ref()` calls
   causing type inference issues.
 
-  - [#717](https://github.com/ClementTsang/bottom/pull/717): Fix clicking on empty space in tables selecting the very last entry of a list in some cases.
+- [#717](https://github.com/ClementTsang/bottom/pull/717): Fix clicking on empty space in tables selecting the very last entry of a list in some cases.
 
 ## Changes
 
@@ -22,6 +22,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - [#676](https://github.com/ClementTsang/bottom/pull/676): Adds support for NVIDIA GPU temperature sensors.
 
+- [#760](https://github.com/ClementTsang/bottom/pull/760): Adds a check for whether bottom is being run in a terminal.
+
 ## [0.6.8] - 2022-02-01
 
 ## Bug Fixes

src/bin/main.rs

@@ -33,6 +33,10 @@ fn main() -> Result<()> {
         utils::logging::init_logger(log::LevelFilter::Debug, std::ffi::OsStr::new("debug.log"))?;
     }
 
+    // Check if the current environment is in a terminal.
+    check_if_terminal();
+
+    // Read from config file.
     let config_path = read_config(matches.value_of("config_location"))
         .context("Unable to access the given config file location.")?;
     let mut config: Config = create_or_get_config(&config_path)

src/lib.rs

@@ -16,7 +16,7 @@ extern crate log;
 use std::{
     boxed::Box,
     fs,
-    io::{stdout, Write},
+    io::{stderr, stdout, Write},
     panic::PanicInfo,
     path::PathBuf,
     sync::Arc,
@@ -271,15 +271,22 @@ pub fn cleanup_terminal(
     )?;
     terminal.show_cursor()?;
 
-    // if is_debug {
-    //     let mut tmp_dir = std::env::temp_dir();
-    //     tmp_dir.push("bottom_debug.log");
-    //     println!("Your debug file is located at {:?}", tmp_dir.as_os_str());
-    // }
-
     Ok(())
 }
 
+/// Check and report to the user if the current environment is not a terminal.
+pub fn check_if_terminal() {
+    use crossterm::tty::IsTty;
+
+    if !stdout().is_tty() {
+        eprintln!(
+            "Warning: bottom is not being output to a terminal. Things might not work properly."
+        );
+        stderr().flush().unwrap();
+        thread::sleep(Duration::from_secs(1));
+    }
+}
+
 /// A panic hook to properly restore the terminal in the case of a panic.
 /// Based on [spotify-tui's implementation](https://github.com/Rigellute/spotify-tui/blob/master/src/main.rs).
 pub fn panic_hook(panic_info: &PanicInfo<'_>) {