Don't search stdout redirected file.

When running ripgrep like this:

    rg foo > output

we must be careful not to search `output` since ripgrep is actively writing
to it. Searching it can cause massive blowups where the file grows without
bound.

While this is conceptually easy to fix (check the inode of the redirection
and the inode of the file you're about to search), there are a few problems
with it.

First, inodes are a Unix thing, so we need a Windows specific solution to
this as well. To resolve this concern, I created a new crate, `same-file`,
which provides a cross platform abstraction.

Second, stat'ing every file is costly. This is not avoidable on Windows,
but on Unix, we can get the inode number directly from directory traversal.
However, this information wasn't exposed, but now it is (through both the
ignore and walkdir crates).

Fixes #286

7 files changed, 241 insertions, 69 deletions

diff --git a/Cargo.lock b/Cargo.lock
index 3fcef67f..d3e9bcf5 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2,19 +2,20 @@
 name = "ripgrep"
 version = "0.3.2"
 dependencies = [
- "bytecount 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)",
+ "bytecount 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "clap 2.19.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "env_logger 0.3.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "grep 0.1.4",
  "ignore 0.1.6",
  "kernel32-sys 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "lazy_static 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.18 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.19 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)",
- "memchr 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "memchr 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "memmap 0.5.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "num_cpus 1.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "num_cpus 1.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "regex 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "same-file 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "termcolor 0.1.1",
  "winapi 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -24,7 +25,7 @@ name = "aho-corasick"
 version = "0.6.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "memchr 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "memchr 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -39,7 +40,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "bytecount"
-version = "0.1.4"
+version = "0.1.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "simd 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -52,7 +53,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "ansi_term 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "bitflags 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.18 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.19 (registry+https://github.com/rust-lang/crates.io-index)",
  "strsim 0.5.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "term_size 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "unicode-segmentation 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -84,7 +85,7 @@ version = "0.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "kernel32-sys 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.18 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.19 (registry+https://github.com/rust-lang/crates.io-index)",
  "winapi 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -96,7 +97,7 @@ dependencies = [
  "fnv 1.0.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "lazy_static 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)",
- "memchr 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "memchr 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "regex 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -105,7 +106,7 @@ name = "grep"
 version = "0.1.4"
 dependencies = [
  "log 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)",
- "memchr 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "memchr 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "regex 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "regex-syntax 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -118,10 +119,10 @@ dependencies = [
  "globset 0.1.2",
  "lazy_static 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)",
- "memchr 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "memchr 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "regex 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "thread_local 0.3.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "walkdir 1.0.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "walkdir 1.0.7 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -140,7 +141,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "libc"
-version = "0.2.18"
+version = "0.2.19"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
@@ -150,10 +151,10 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "memchr"
-version = "1.0.0"
+version = "1.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "libc 0.2.18 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.19 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -163,16 +164,16 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "fs2 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "kernel32-sys 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.18 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.19 (registry+https://github.com/rust-lang/crates.io-index)",
  "winapi 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "num_cpus"
-version = "1.2.0"
+version = "1.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "libc 0.2.18 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.19 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -181,7 +182,7 @@ version = "0.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "aho-corasick 0.6.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "memchr 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "memchr 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "regex-syntax 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "simd 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "thread_local 0.3.2 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -194,6 +195,16 @@ version = "0.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
+name = "same-file"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "kernel32-sys 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.19 (registry+https://github.com/rust-lang/crates.io-index)",
+ "winapi 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
 name = "simd"
 version = "0.1.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -209,7 +220,7 @@ version = "0.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "kernel32-sys 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.18 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.19 (registry+https://github.com/rust-lang/crates.io-index)",
  "winapi 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -226,7 +237,7 @@ version = "3.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "kernel32-sys 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.18 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.19 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -273,10 +284,11 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "walkdir"
-version = "1.0.3"
+version = "1.0.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "kernel32-sys 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "same-file 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "winapi 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -302,7 +314,7 @@ dependencies = [
 "checksum aho-corasick 0.6.1 (registry+https://github.com/rust-lang/crates.io-index)" = "4f660b942762979b56c9f07b4b36bb559776fbad102f05d6771e1b629e8fd5bf"
 "checksum ansi_term 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)" = "23ac7c30002a5accbf7e8987d0632fa6de155b7c3d39d0067317a391e00a2ef6"
 "checksum bitflags 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)" = "aad18937a628ec6abcd26d1489012cc0e18c21798210f491af69ded9b881106d"
-"checksum bytecount 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)" = "49e3c21915578e2300b08d3c174a8ac887e0c6421dff86fdc4d741dc29e5d413"
+"checksum bytecount 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)" = "289e7bdb4fb98f273dd0628a8be7ffe76aa9b944464f074b9c4f82000a580aed"
 "checksum clap 2.19.3 (registry+https://github.com/rust-lang/crates.io-index)" = "95b78f3fe0fc94c13c731714363260e04b557a637166f33a4570d3189d642374"
 "checksum crossbeam 0.2.10 (registry+https://github.com/rust-lang/crates.io-index)" = "0c5ea215664ca264da8a9d9c3be80d2eaf30923c259d03e870388eb927508f97"
 "checksum env_logger 0.3.5 (registry+https://github.com/rust-lang/crates.io-index)" = "15abd780e45b3ea4f76b4e9a26ff4843258dd8a3eed2775a0e7368c2e7936c2f"
@@ -310,13 +322,14 @@ dependencies = [
 "checksum fs2 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)" = "640001e1bd865c7c32806292822445af576a6866175b5225aa2087ca5e3de551"
 "checksum kernel32-sys 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)" = "7507624b29483431c0ba2d82aece8ca6cdba9382bff4ddd0f7490560c056098d"
 "checksum lazy_static 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)" = "6abe0ee2e758cd6bc8a2cd56726359007748fbf4128da998b65d0b70f881e19b"
-"checksum libc 0.2.18 (registry+https://github.com/rust-lang/crates.io-index)" = "a51822fc847e7a8101514d1d44e354ba2ffa7d4c194dcab48870740e327cac70"
+"checksum libc 0.2.19 (registry+https://github.com/rust-lang/crates.io-index)" = "9e030dc72013ed68994d1b2cbf36a94dd0e58418ba949c4b0db7eeb70a7a6352"
 "checksum log 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)" = "ab83497bf8bf4ed2a74259c1c802351fcd67a65baa86394b6ba73c36f4838054"
-"checksum memchr 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)" = "7492849298f0731c393b1f34ce03a7c84c00bead2e7057db9342907c8fdcae28"
+"checksum memchr 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)" = "1dbccc0e46f1ea47b9f17e6d67c5a96bd27030519c519c9c91327e31275a47b4"
 "checksum memmap 0.5.0 (registry+https://github.com/rust-lang/crates.io-index)" = "065ce59af31c18ea2c419100bda6247dd4ec3099423202b12f0bd32e529fabd2"
-"checksum num_cpus 1.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "55aabf4e2d6271a2e4e4c0f2ea1f5b07cc589cc1a9e9213013b54a76678ca4f3"
+"checksum num_cpus 1.2.1 (registry+https://github.com/rust-lang/crates.io-index)" = "a225d1e2717567599c24f88e49f00856c6e825a12125181ee42c4257e3688d39"
 "checksum regex 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)" = "4278c17d0f6d62dfef0ab00028feb45bd7d2102843f80763474eeb1be8a10c01"
 "checksum regex-syntax 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "2f9191b1f57603095f105d317e375d19b1c9c5c3185ea9633a99a6dcbed04457"
+"checksum same-file 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)" = "05f5dc7680f4bdc74fa0df5f32fcbaf1174a92e65bf3d69e0288248604306875"
 "checksum simd 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)" = "63b5847c2d766ca7ce7227672850955802fabd779ba616aeabead4c2c3877023"
 "checksum strsim 0.5.2 (registry+https://github.com/rust-lang/crates.io-index)" = "67f84c44fbb2f91db7fef94554e6b2ac05909c9c0b0bc23bb98d3a1aebfe7f7c"
 "checksum term_size 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)" = "3f7f5f3f71b0040cecc71af239414c23fd3c73570f5ff54cf50e03cef637f2a0"
@@ -328,6 +341,6 @@ dependencies = [
 "checksum utf8-ranges 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)" = "662fab6525a98beff2921d7f61a39e7d59e0b425ebc7d0d9e66d316e55124122"
 "checksum vec_map 0.6.0 (registry+https://github.com/rust-lang/crates.io-index)" = "cac5efe5cb0fa14ec2f84f83c701c562ee63f6dcc680861b21d65c682adfb05f"
 "checksum void 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)" = "6a02e4885ed3bc0f2de90ea6dd45ebcbb66dacffe03547fadbb0eeae2770887d"
-"checksum walkdir 1.0.3 (registry+https://github.com/rust-lang/crates.io-index)" = "dd7c16466ecc507c7cb5988db03e6eab4aaeab89a5c37a29251fcfd3ac9b7afe"
+"checksum walkdir 1.0.7 (registry+https://github.com/rust-lang/crates.io-index)" = "bb08f9e670fab86099470b97cd2b252d6527f0b3cc1401acdb595ffc9dd288ff"
 "checksum winapi 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)" = "167dc9d6949a9b857f3451275e911c3f44255842c1f7a76f33c55103a909087a"
 "checksum winapi-build 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)" = "2d315eee3b34aca4797b2da6b13ed88266e6d612562a0c46390af8299fc699bc"
diff --git a/Cargo.toml b/Cargo.toml
index ce497a11..d671cbba 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -37,6 +37,7 @@ memchr = "1"
 memmap = "0.5"
 num_cpus = "1"
 regex = "0.2.0"
+same-file = "0.1.1"
 termcolor = { version = "0.1.0", path = "termcolor" }
 
 [target.'cfg(windows)'.dependencies]
diff --git a/ignore/Cargo.toml b/ignore/Cargo.toml
index dc903783..238fe44e 100644
--- a/ignore/Cargo.toml
+++ b/ignore/Cargo.toml
@@ -25,7 +25,7 @@ log = "0.3"
 memchr = "1"
 regex = "0.2.0"
 thread_local = "0.3.2"
-walkdir = "1"
+walkdir = "1.0.7"
 
 [dev-dependencies]
 tempdir = "0.3.5"
diff --git a/ignore/src/walk.rs b/ignore/src/walk.rs
index e1dd2052..860f26d8 100644
--- a/ignore/src/walk.rs
+++ b/ignore/src/walk.rs
@@ -72,6 +72,14 @@ impl DirEntry {
         self.dent.depth()
     }
 
+    /// Returns the underlying inode number if one exists.
+    ///
+    /// If this entry doesn't have an inode number, then `None` is returned.
+    #[cfg(unix)]
+    pub fn ino(&self) -> Option<u64> {
+        self.dent.ino()
+    }
+
     /// Returns an error, if one exists, associated with processing this entry.
     ///
     /// An example of an error is one that occurred while parsing an ignore
@@ -188,6 +196,16 @@ impl DirEntryInner {
             Raw(ref x) => x.depth(),
         }
     }
+
+    #[cfg(unix)]
+    fn ino(&self) -> Option<u64> {
+        use self::DirEntryInner::*;
+        match *self {
+            Stdin => None,
+            Walkdir(ref x) => Some(x.ino()),
+            Raw(ref x) => Some(x.ino()),
+        }
+    }
 }
 
 /// DirEntryRaw is essentially copied from the walkdir crate so that we can
@@ -203,6 +221,9 @@ struct DirEntryRaw {
     follow_link: bool,
     /// The depth at which this entry was generated relative to the root.
     depth: usize,
+    /// The underlying inode number (Unix only).
+    #[cfg(unix)]
+    ino: u64,
 }
 
 impl fmt::Debug for DirEntryRaw {
@@ -247,6 +268,11 @@ impl DirEntryRaw {
         self.depth
     }
 
+    #[cfg(unix)]
+    fn ino(&self) -> u64 {
+        self.ino
+    }
+
     fn from_entry(
         depth: usize,
         ent: &fs::DirEntry,
@@ -258,15 +284,57 @@ impl DirEntryRaw {
                 err: Box::new(err),
             }
         }));
-        Ok(DirEntryRaw {
+        Ok(DirEntryRaw::from_entry_os(depth, ent, ty))
+    }
+
+    #[cfg(not(unix))]
+    fn from_entry_os(
+        depth: usize,
+        ent: &fs::DirEntry,
+        ty: fs::FileType,
+    ) -> DirEntryRaw {
+        DirEntryRaw {
             path: ent.path(),
             ty: ty,
             follow_link: false,
             depth: depth,
+        }
+    }
+
+    #[cfg(unix)]
+    fn from_entry_os(
+        depth: usize,
+        ent: &fs::DirEntry,
+        ty: fs::FileType,
+    ) -> DirEntryRaw {
+        use std::os::unix::fs::DirEntryExt;
+
+        DirEntryRaw {
+            path: ent.path(),
+            ty: ty,
+            follow_link: false,
+            depth: depth,
+            ino: ent.ino(),
+        }
+    }
+
+    #[cfg(not(unix))]
+    fn from_link(depth: usize, pb: PathBuf) -> Result<DirEntryRaw, Error> {
+        let md = try!(fs::metadata(&pb).map_err(|err| {
+            Error::Io(err).with_path(&pb)
+        }));
+        Ok(DirEntryRaw {
+            path: pb,
+            ty: md.file_type(),
+            follow_link: true,
+            depth: depth,
         })
     }
 
+    #[cfg(unix)]
     fn from_link(depth: usize, pb: PathBuf) -> Result<DirEntryRaw, Error> {
+        use std::os::unix::fs::MetadataExt;
+
         let md = try!(fs::metadata(&pb).map_err(|err| {
             Error::Io(err).with_path(&pb)
         }));
@@ -275,6 +343,7 @@ impl DirEntryRaw {
             ty: md.file_type(),
             follow_link: true,
             depth: depth,
+            ino: md.ino(),
         })
     }
 }
diff --git a/src/args.rs b/src/args.rs
index 6aec396b..29a7fa81 100644
--- a/src/args.rs
+++ b/src/args.rs
@@ -15,6 +15,7 @@ use grep::{Grep, GrepBuilder};
 use log;
 use num_cpus;
 use regex;
+use same_file;
 use termcolor;
 
 use app;
@@ -65,6 +66,7 @@ pub struct Args {
     quiet_matched: QuietMatched,
     replace: Option<Vec<u8>>,
     sort_files: bool,
+    stdout_handle: Option<same_file::Handle>,
     text: bool,
     threads: usize,
     type_list: bool,
@@ -182,6 +184,17 @@ impl Args {
         termcolor::Stdout::new(self.color_choice)
     }
 
+    /// Returns a handle to stdout for filtering search.
+    ///
+    /// A handle is returned if and only if ripgrep's stdout is being
+    /// redirected to a file. The handle returned corresponds to that file.
+    ///
+    /// This can be used to ensure that we do not attempt to search a file
+    /// that ripgrep is writing to.
+    pub fn stdout_handle(&self) -> Option<&same_file::Handle> {
+        self.stdout_handle.as_ref()
+    }
+
     /// Create a new buffer writer for multi-threaded searching with color
     /// support.
     pub fn buffer_writer(&self) -> termcolor::BufferWriter {
@@ -338,6 +351,7 @@ impl<'a> ArgMatches<'a> {
             quiet_matched: QuietMatched::new(quiet),
             replace: self.replace(),
             sort_files: self.is_present("sort-files"),
+            stdout_handle: self.stdout_handle(),
             text: self.text(),
             threads: try!(self.threads()),
             type_list: self.is_present("type-list"),
@@ -518,6 +532,28 @@ impl<'a> ArgMatches<'a> {
         }
     }
 
+    /// Returns a handle to stdout for filtering search.
+    ///
+    /// A handle is returned if and only if ripgrep's stdout is being
+    /// redirected to a file. The handle returned corresponds to that file.
+    ///
+    /// This can be used to ensure that we do not attempt to search a file
+    /// that ripgrep is writing to.
+    fn stdout_handle(&self) -> Option<same_file::Handle> {
+        let h = match same_file::Handle::stdout() {
+            Err(_) => return None,
+            Ok(h) => h,
+        };
+        let md = match h.as_file().metadata() {
+            Err(_) => return None,
+            Ok(md) => md,
+        };
+        if !md.is_file() {
+            return None;
+        }
+        Some(h)
+    }
+
     /// Returns true if and only if memory map searching should be tried.
     ///
     /// `paths` should be a slice of all top-level file paths that ripgrep
diff --git a/src/atty.rs b/src/atty.rs
index 9e96fe6e..cb10c1dc 100644
--- a/src/atty.rs
+++ b/src/atty.rs
@@ -11,15 +11,10 @@ use winapi::winnt::HANDLE;
 
 #[cfg(unix)]
 pub fn stdin_is_readable() -> bool {
-    use std::fs::File;
     use std::os::unix::fs::FileTypeExt;
-    use std::os::unix::io::{FromRawFd, IntoRawFd};
-    use libc;
+    use same_file::Handle;
 
-    let file = unsafe { File::from_raw_fd(libc::STDIN_FILENO) };
-    let md = file.metadata();
-    let _ = file.into_raw_fd();
-    let ft = match md {
+    let ft = match Handle::stdin().and_then(|h| h.as_file().metadata()) {
         Err(_) => return false,
         Ok(md) => md.file_type(),
     };
@@ -101,7 +96,7 @@ pub fn on_stdout() -> bool {
 
 /// Returns true if there is an MSYS tty on the given handle.
 #[cfg(windows)]
-fn msys_tty_on_handle(handle: HANDLE) -> bool {
+unsafe fn msys_tty_on_handle(handle: HANDLE) -> bool {
     use std::ffi::OsString;
     use std::mem;
     use std::os::raw::c_void;
@@ -113,27 +108,25 @@ fn msys_tty_on_handle(handle: HANDLE) -> bool {
     use winapi::minwinbase::FileNameInfo;
     use winapi::minwindef::MAX_PATH;
 
-    unsafe {
-        let size = mem::size_of::<FILE_NAME_INFO>();
-        let mut name_info_bytes = vec![0u8; size + MAX_PATH];
-        let res = GetFileInformationByHandleEx(
-            handle,
-            FileNameInfo,
-            &mut *name_info_bytes as *mut _ as *mut c_void,
-            name_info_bytes.len() as u32);
-        if res == 0 {
-            return true;
-        }
-        let name_info: FILE_NAME_INFO =
-            *(name_info_bytes[0..size].as_ptr() as *const FILE_NAME_INFO);
-        let name_bytes =
-            &name_info_bytes[size..size + name_info.FileNameLength as usize];
-        let name_u16 = slice::from_raw_parts(
-            name_bytes.as_ptr() as *const u16, name_bytes.len() / 2);
-        let name = OsString::from_wide(name_u16)
-            .as_os_str().to_string_lossy().into_owned();
-        name.contains("msys-") || name.contains("-pty")
+    let size = mem::size_of::<FILE_NAME_INFO>();
+    let mut name_info_bytes = vec![0u8; size + MAX_PATH];
+    let res = GetFileInformationByHandleEx(
+        handle,
+        FileNameInfo,
+        &mut *name_info_bytes as *mut _ as *mut c_void,
+        name_info_bytes.len() as u32);
+    if res == 0 {
+        return true;
     }
+    let name_info: FILE_NAME_INFO =
+        *(name_info_bytes[0..size].as_ptr() as *const FILE_NAME_INFO);
+    let name_bytes =
+        &name_info_bytes[size..size + name_info.FileNameLength as usize];
+    let name_u16 = slice::from_raw_parts(
+        name_bytes.as_ptr() as *const u16, name_bytes.len() / 2);
+    let name = OsString::from_wide(name_u16)
+        .as_os_str().to_string_lossy().into_owned();
+    name.contains("msys-") || name.contains("-pty")
 }
 
 /// Returns true if there is a console on the given file descriptor.
@@ -145,8 +138,8 @@ unsafe fn console_on_fd(fd: DWORD) -> bool {
 
 /// Returns true if there is a console on the given handle.
 #[cfg(windows)]
-fn console_on_handle(handle: HANDLE) -> bool {
+unsafe fn console_on_handle(handle: HANDLE) -> bool {
     use kernel32::GetConsoleMode;
     let mut out = 0;
-    unsafe { GetConsoleMode(handle, &mut out) != 0 }
+    GetConsoleMode(handle, &mut out) != 0
 }
diff --git a/src/main.rs b/src/main.rs
index 236c093e..735298f9 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -15,6 +15,7 @@ extern crate memchr;
 extern crate memmap;
 extern crate num_cpus;
 extern crate regex;
+extern crate same_file;
 extern crate termcolor;
 #[cfg(windows)]
 extern crate winapi;
@@ -106,7 +107,11 @@ fn run_parallel(args: Arc<Args>) -> Result<u64> {
             if quiet_matched.has_match() {
                 return Quit;
             }
-            let dent = match get_or_log_dir_entry(result, args.no_messages()) {
+            let dent = match get_or_log_dir_entry(
+                result,
+                args.stdout_handle(),
+                args.no_messages(),
+            ) {
                 None => return Continue,
                 Some(dent) => dent,
             };
@@ -148,7 +153,11 @@ fn run_one_thread(args: Arc<Args>) -> Result<u64> {
     let mut paths_searched: u64 = 0;
     let mut match_count = 0;
     for result in args.walker() {
-        let dent = match get_or_log_dir_entry(result, args.no_messages()) {
+        let dent = match get_or_log_dir_entry(
+            result,
+            args.stdout_handle(),
+            args.no_messages(),
+        ) {
             None => continue,
             Some(dent) => dent,
         };
@@ -190,11 +199,15 @@ fn run_files_parallel(args: Arc<Args>) -> Result<u64> {
         }
         file_count
     });
-    let no_messages = args.no_messages();
     args.walker_parallel().run(move || {
+        let args = args.clone();
         let tx = tx.clone();
         Box::new(move |result| {
-            if let Some(dent) = get_or_log_dir_entry(result, no_messages) {
+            if let Some(dent) = get_or_log_dir_entry(
+                result,
+                args.stdout_handle(),
+                args.no_messages(),
+            ) {
                 tx.send(dent).unwrap();
             }
             ignore::WalkState::Continue
@@ -208,7 +221,11 @@ fn run_files_one_thread(args: Arc<Args>) -> Result<u64> {
     let mut printer = args.printer(stdout.lock());
     let mut file_count = 0;
     for result in args.walker() {
-        let dent = match get_or_log_dir_entry(result, args.no_messages()) {
+        let dent = match get_or_log_dir_entry(
+            result,
+            args.stdout_handle(),
+            args.no_messages(),
+        ) {
             None => continue,
             Some(dent) => dent,
         };
@@ -231,6 +248,7 @@ fn run_types(args: Arc<Args>) -> Result<u64> {
 
 fn get_or_log_dir_entry(
     result: result::Result<ignore::DirEntry, ignore::Error>,
+    stdout_handle: Option<&same_file::Handle>,
     no_messages: bool,
 ) -> Option<ignore::DirEntry> {
     match result {
@@ -253,16 +271,58 @@ fn get_or_log_dir_entry(
             // A depth of 0 means the user gave the path explicitly, so we
             // should always try to search it.
             if dent.depth() == 0 && !ft.is_dir() {
-                Some(dent)
-            } else if ft.is_file() {
-                Some(dent)
-            } else {
-                None
+                return Some(dent);
+            } else if !ft.is_file() {
+                return None;
+            }
+            // If we are redirecting stdout to a file, then don't search that
+            // file.
+            if is_stdout_file(&dent, stdout_handle, no_messages) {
+                return None;
+            }
+            Some(dent)
+        }
+    }
+}
+
+fn is_stdout_file(
+    dent: &ignore::DirEntry,
+    stdout_handle: Option<&same_file::Handle>,
+    no_messages: bool,
+) -> bool {
+    let stdout_handle = match stdout_handle {
+        None => return false,
+        Some(stdout_handle) => stdout_handle,
+    };
+    // If we know for sure that these two things aren't equal, then avoid
+    // the costly extra stat call to determine equality.
+    if !maybe_dent_eq_handle(dent, stdout_handle) {
+        return false;
+    }
+    match same_file::Handle::from_path(dent.path()) {
+        Ok(h) => stdout_handle == &h,
+        Err(err) => {
+            if !no_messages {
+                eprintln!("{}: {}", dent.path().display(), err);
             }
+            false
         }
     }
 }
 
+#[cfg(unix)]
+fn maybe_dent_eq_handle(
+    dent: &ignore::DirEntry,
+    handle: &same_file::Handle,
+) -> bool {
+    dent.ino() == Some(handle.ino())
+}
+
+#[cfg(not(unix))]
+fn maybe_dent_eq_handle(_: &ignore::DirEntry, _: &same_file::Handle) -> bool {
+    true
+}
+
 fn eprint_nothing_searched() {
     eprintln!("No files were searched, which means ripgrep probably \
                applied a filter you didn't expect. \