Detect infinite r/w loop on unix systems

Author: niklasmohrin

Cargo.lock

@@ -51,6 +51,7 @@ serde = { version = "1.0", features = ["derive"] }
 serde_yaml = "0.8"
 semver = "0.10"
 path_abs = { version = "0.5", default-features = false }
+nix = "0.18.0"
 
 [dependencies.git2]
 version = "0.13"

Cargo.toml

@@ -63,6 +63,28 @@ impl<'b> Controller<'b> {
         }
 
         let attached_to_pager = output_type.is_pager();
+
+        #[cfg(not(target_os = "windows"))]
+        if !attached_to_pager {
+            use nix::sys::stat::fstat;
+            use std::os::unix::io::AsRawFd;
+            // Check whether any of the inputs is the same as the output (i.e. bat a b c > b)
+            // to avoid an infinite loop.
+            // We cannot detect this, if the output is piped into less (i.e. bat a b c | less > b).
+            let out_stats = fstat(io::stdout().as_raw_fd()).unwrap();
+            let out_dev = out_stats.st_dev;
+            let out_ino = out_stats.st_ino;
+
+            if inputs
+                .iter()
+                .flat_map(|input| input.kind.stat())
+                .any(|stats| stats.st_dev == out_dev && stats.st_ino == out_ino)
+            {
+                eprintln!("Duplicate files detected!");
+                return Ok(false);
+            }
+        }
+
         let writer = output_type.handle()?;
         let mut no_errors: bool = true;
 

src/controller.rs

@@ -1,8 +1,12 @@
 use std::ffi::{OsStr, OsString};
 use std::fs::File;
 use std::io::{self, BufRead, BufReader, Read};
+#[cfg(not(target_os = "windows"))]
+use std::os::unix::io::AsRawFd;
 
 use content_inspector::{self, ContentType};
+#[cfg(not(target_os = "windows"))]
+use nix::sys::stat::{fstat, stat, FileStat};
 
 use crate::error::*;
 
@@ -80,6 +84,15 @@ impl<'a> InputKind<'a> {
             InputKind::CustomReader(_) => InputDescription::new("READER"),
         }
     }
+
+    #[cfg(not(target_os = "windows"))]
+    pub fn stat(&self) -> Option<FileStat> {
+        match self {
+            InputKind::OrdinaryFile(ref path) => stat(path.as_os_str()).ok(),
+            InputKind::StdIn => fstat(io::stdin().as_raw_fd()).ok(),
+            InputKind::CustomReader(_) => None,
+        }
+    }
 }
 
 #[derive(Clone, Default)]