Merge pull request #7253 from karlmcdowall/head_stdio_file

Head: ensure stdin input stream is correct on exit

src/uu/head/src/head.rs

@@ -7,8 +7,12 @@
 
 use clap::{crate_version, Arg, ArgAction, ArgMatches, Command};
 use std::ffi::OsString;
+#[cfg(unix)]
+use std::fs::File;
 use std::io::{self, BufWriter, Read, Seek, SeekFrom, Write};
 use std::num::TryFromIntError;
+#[cfg(unix)]
+use std::os::fd::{AsRawFd, FromRawFd};
 use thiserror::Error;
 use uucore::display::Quotable;
 use uucore::error::{FromIo, UError, UResult};
@@ -239,7 +243,7 @@ impl HeadOptions {
     }
 }
 
-fn read_n_bytes(input: impl Read, n: u64) -> std::io::Result<()> {
+fn read_n_bytes(input: impl Read, n: u64) -> std::io::Result<u64> {
     // Read the first `n` bytes from the `input` reader.
     let mut reader = input.take(n);
 
@@ -247,31 +251,31 @@ fn read_n_bytes(input: impl Read, n: u64) -> std::io::Result<()> {
     let stdout = std::io::stdout();
     let mut stdout = stdout.lock();
 
-    io::copy(&mut reader, &mut stdout)?;
+    let bytes_written = io::copy(&mut reader, &mut stdout)?;
 
     // Make sure we finish writing everything to the target before
     // exiting. Otherwise, when Rust is implicitly flushing, any
     // error will be silently ignored.
     stdout.flush()?;
 
-    Ok(())
+    Ok(bytes_written)
 }
 
-fn read_n_lines(input: &mut impl std::io::BufRead, n: u64, separator: u8) -> std::io::Result<()> {
+fn read_n_lines(input: &mut impl std::io::BufRead, n: u64, separator: u8) -> std::io::Result<u64> {
     // Read the first `n` lines from the `input` reader.
     let mut reader = take_lines(input, n, separator);
 
     // Write those bytes to `stdout`.
     let mut stdout = std::io::stdout();
 
-    io::copy(&mut reader, &mut stdout)?;
+    let bytes_written = io::copy(&mut reader, &mut stdout)?;
 
     // Make sure we finish writing everything to the target before
     // exiting. Otherwise, when Rust is implicitly flushing, any
     // error will be silently ignored.
     stdout.flush()?;
 
-    Ok(())
+    Ok(bytes_written)
 }
 
 fn catch_too_large_numbers_in_backwards_bytes_or_lines(n: u64) -> Option<usize> {
@@ -284,7 +288,8 @@ fn catch_too_large_numbers_in_backwards_bytes_or_lines(n: u64) -> Option<usize>
     }
 }
 
-fn read_but_last_n_bytes(input: impl std::io::BufRead, n: u64) -> std::io::Result<()> {
+fn read_but_last_n_bytes(input: impl std::io::BufRead, n: u64) -> std::io::Result<u64> {
+    let mut bytes_written = 0;
     if let Some(n) = catch_too_large_numbers_in_backwards_bytes_or_lines(n) {
         let stdout = std::io::stdout();
         let stdout = stdout.lock();
@@ -294,32 +299,36 @@ fn read_but_last_n_bytes(input: impl std::io::BufRead, n: u64) -> std::io::Resul
         let mut writer = BufWriter::with_capacity(BUF_SIZE, stdout);
         for byte in take_all_but(input.bytes(), n) {
             writer.write_all(&[byte?])?;
+            bytes_written += 1;
         }
         // Make sure we finish writing everything to the target before
         // exiting. Otherwise, when Rust is implicitly flushing, any
         // error will be silently ignored.
         writer.flush()?;
     }
-    Ok(())
+    Ok(bytes_written)
 }
 
 fn read_but_last_n_lines(
     input: impl std::io::BufRead,
     n: u64,
     separator: u8,
-) -> std::io::Result<()> {
+) -> std::io::Result<u64> {
+    let mut bytes_written: u64 = 0;
     if let Some(n) = catch_too_large_numbers_in_backwards_bytes_or_lines(n) {
         let stdout = std::io::stdout();
         let mut stdout = stdout.lock();
         for bytes in take_all_but(lines(input, separator), n) {
-            stdout.write_all(&bytes?)?;
+            let bytes = bytes?;
+            bytes_written += u64::try_from(bytes.len()).unwrap();
+            stdout.write_all(&bytes)?;
         }
         // Make sure we finish writing everything to the target before
         // exiting. Otherwise, when Rust is implicitly flushing, any
         // error will be silently ignored.
         stdout.flush()?;
     }
-    Ok(())
+    Ok(bytes_written)
 }
 
 /// Return the index in `input` just after the `n`th line from the end.
@@ -400,45 +409,43 @@ fn is_seekable(input: &mut std::fs::File) -> bool {
         && input.seek(SeekFrom::Start(current_pos.unwrap())).is_ok()
 }
 
-fn head_backwards_file(input: &mut std::fs::File, options: &HeadOptions) -> std::io::Result<()> {
+fn head_backwards_file(input: &mut std::fs::File, options: &HeadOptions) -> std::io::Result<u64> {
     let st = input.metadata()?;
     let seekable = is_seekable(input);
     let blksize_limit = uucore::fs::sane_blksize::sane_blksize_from_metadata(&st);
     if !seekable || st.len() <= blksize_limit {
-        return head_backwards_without_seek_file(input, options);
+        head_backwards_without_seek_file(input, options)
-    }
+    } else {
-
         head_backwards_on_seekable_file(input, options)
+    }
 }
 
 fn head_backwards_without_seek_file(
     input: &mut std::fs::File,
     options: &HeadOptions,
-) -> std::io::Result<()> {
+) -> std::io::Result<u64> {
     let reader = std::io::BufReader::with_capacity(BUF_SIZE, &*input);
     match options.mode {
-        Mode::AllButLastBytes(n) => read_but_last_n_bytes(reader, n)?,
+        Mode::AllButLastBytes(n) => read_but_last_n_bytes(reader, n),
-        Mode::AllButLastLines(n) => read_but_last_n_lines(reader, n, options.line_ending.into())?,
+        Mode::AllButLastLines(n) => read_but_last_n_lines(reader, n, options.line_ending.into()),
         _ => unreachable!(),
     }
-
-    Ok(())
 }
 
 fn head_backwards_on_seekable_file(
     input: &mut std::fs::File,
     options: &HeadOptions,
-) -> std::io::Result<()> {
+) -> std::io::Result<u64> {
     match options.mode {
         Mode::AllButLastBytes(n) => {
             let size = input.metadata()?.len();
             if n >= size {
-                return Ok(());
+                Ok(0)
             } else {
                 read_n_bytes(
                     &mut std::io::BufReader::with_capacity(BUF_SIZE, input),
                     size - n,
-                )?;
+                )
             }
         }
         Mode::AllButLastLines(n) => {
@@ -446,14 +453,13 @@ fn head_backwards_on_seekable_file(
             read_n_bytes(
                 &mut std::io::BufReader::with_capacity(BUF_SIZE, input),
                 found,
-            )?;
+            )
         }
         _ => unreachable!(),
     }
-    Ok(())
 }
 
-fn head_file(input: &mut std::fs::File, options: &HeadOptions) -> std::io::Result<()> {
+fn head_file(input: &mut std::fs::File, options: &HeadOptions) -> std::io::Result<u64> {
     match options.mode {
         Mode::FirstBytes(n) => {
             read_n_bytes(&mut std::io::BufReader::with_capacity(BUF_SIZE, input), n)
@@ -480,16 +486,41 @@ fn uu_head(options: &HeadOptions) -> UResult<()> {
                     println!("==> standard input <==");
                 }
                 let stdin = std::io::stdin();
+
+                #[cfg(unix)]
+                {
+                    let stdin_raw_fd = stdin.as_raw_fd();
+                    let mut stdin_file = unsafe { File::from_raw_fd(stdin_raw_fd) };
+                    let current_pos = stdin_file.stream_position();
+                    if let Ok(current_pos) = current_pos {
+                        // We have a seekable file. Ensure we set the input stream to the
+                        // last byte read so that any tools that parse the remainder of
+                        // the stdin stream read from the correct place.
+
+                        let bytes_read = head_file(&mut stdin_file, options)?;
+                        stdin_file.seek(SeekFrom::Start(current_pos + bytes_read))?;
+                    } else {
+                        let _bytes_read = head_file(&mut stdin_file, options)?;
+                    }
+                }
+
+                #[cfg(not(unix))]
+                {
                     let mut stdin = stdin.lock();
 
                     match options.mode {
                         Mode::FirstBytes(n) => read_n_bytes(&mut stdin, n),
                         Mode::AllButLastBytes(n) => read_but_last_n_bytes(&mut stdin, n),
-                    Mode::FirstLines(n) => read_n_lines(&mut stdin, n, options.line_ending.into()),
+                        Mode::FirstLines(n) => {
+                            read_n_lines(&mut stdin, n, options.line_ending.into())
+                        }
                         Mode::AllButLastLines(n) => {
                             read_but_last_n_lines(&mut stdin, n, options.line_ending.into())
                         }
+                    }?;
                 }
+
+                Ok(())
             }
             (name, false) => {
                 let mut file = match std::fs::File::open(name) {
@@ -508,7 +539,8 @@ fn uu_head(options: &HeadOptions) -> UResult<()> {
                     }
                     println!("==> {name} <==");
                 }
-                head_file(&mut file, options)
+                head_file(&mut file, options)?;
+                Ok(())
             }
         };
         if let Err(e) = res {

tests/by-util/test_head.rs

@@ -7,6 +7,14 @@
 // spell-checker:ignore (words) seekable
 
 use crate::common::util::TestScenario;
+#[cfg(all(
+    not(target_os = "windows"),
+    not(target_os = "macos"),
+    not(target_os = "android"),
+    not(target_os = "freebsd"),
+    not(target_os = "openbsd")
+))]
+use std::io::Read;
 
 static INPUT: &str = "lorem_ipsum.txt";
 
@@ -400,51 +408,51 @@ fn test_all_but_last_bytes_large_file_piped() {
     let fixtures = &scene.fixtures;
 
     // First, create all our fixtures.
-    let seq_30000_file_name = "seq_30000";
+    let seq_20000_file_name = "seq_20000";
-    let seq_29000_file_name = "seq_29000";
+    let seq_19000_file_name = "seq_19000";
-    let seq_29001_30000_file_name = "seq_29001_30000";
+    let seq_19001_20000_file_name = "seq_19001_20000";
     scene
         .cmd("seq")
-        .arg("30000")
+        .arg("20000")
-        .set_stdout(fixtures.make_file(seq_30000_file_name))
+        .set_stdout(fixtures.make_file(seq_20000_file_name))
         .succeeds();
     scene
         .cmd("seq")
-        .arg("29000")
+        .arg("19000")
-        .set_stdout(fixtures.make_file(seq_29000_file_name))
+        .set_stdout(fixtures.make_file(seq_19000_file_name))
         .succeeds();
     scene
         .cmd("seq")
-        .args(&["29001", "30000"])
+        .args(&["19001", "20000"])
-        .set_stdout(fixtures.make_file(seq_29001_30000_file_name))
+        .set_stdout(fixtures.make_file(seq_19001_20000_file_name))
         .succeeds();
 
-    let seq_29001_30000_file_length = fixtures
+    let seq_19001_20000_file_length = fixtures
-        .open(seq_29001_30000_file_name)
+        .open(seq_19001_20000_file_name)
         .metadata()
         .unwrap()
         .len();
     scene
         .ucmd()
-        .args(&["-c", &format!("-{}", seq_29001_30000_file_length)])
+        .args(&["-c", &format!("-{}", seq_19001_20000_file_length)])
-        .pipe_in_fixture(seq_30000_file_name)
+        .pipe_in_fixture(seq_20000_file_name)
         .succeeds()
-        .stdout_only_fixture(seq_29000_file_name);
+        .stdout_only_fixture(seq_19000_file_name);
 }
 
 #[test]
-fn test_read_backwards_lines_large_file() {
+fn test_all_but_last_lines_large_file() {
     // Create our fixtures on the fly. We need the input file to be at least double
     // the size of BUF_SIZE as specified in head.rs. Go for something a bit bigger
     // than that.
     let scene = TestScenario::new(util_name!());
     let fixtures = &scene.fixtures;
-    let seq_30000_file_name = "seq_30000";
+    let seq_20000_file_name = "seq_20000";
     let seq_1000_file_name = "seq_1000";
     scene
         .cmd("seq")
-        .arg("30000")
+        .arg("20000")
-        .set_stdout(fixtures.make_file(seq_30000_file_name))
+        .set_stdout(fixtures.make_file(seq_20000_file_name))
         .succeeds();
     scene
         .cmd("seq")
@@ -455,21 +463,246 @@ fn test_read_backwards_lines_large_file() {
     // Now run our tests.
     scene
         .ucmd()
-        .args(&["-n", "-29000", "seq_30000"])
+        .args(&["-n", "-19000", seq_20000_file_name])
         .succeeds()
-        .stdout_is_fixture("seq_1000");
+        .stdout_only_fixture("seq_1000");
 
     scene
         .ucmd()
-        .args(&["-n", "-30000", "seq_30000"])
+        .args(&["-n", "-20000", seq_20000_file_name])
-        .run()
+        .succeeds()
-        .stdout_is_fixture("emptyfile.txt");
+        .stdout_only_fixture("emptyfile.txt");
 
     scene
         .ucmd()
-        .args(&["-n", "-30001", "seq_30000"])
+        .args(&["-n", "-20001", seq_20000_file_name])
-        .run()
+        .succeeds()
-        .stdout_is_fixture("emptyfile.txt");
+        .stdout_only_fixture("emptyfile.txt");
+}
+
+#[cfg(all(
+    not(target_os = "windows"),
+    not(target_os = "macos"),
+    not(target_os = "android"),
+    not(target_os = "freebsd"),
+    not(target_os = "openbsd")
+))]
+#[test]
+fn test_validate_stdin_offset_lines() {
+    // A handful of unix-only tests to validate behavior when reading from stdin on a seekable
+    // file. GNU-compatibility requires that the stdin file be left such that if another
+    // process is invoked on the same stdin file after head has run, the subsequent file should
+    // start reading from the byte after the last byte printed by head.
+    // Since this is unix-only requirement, keep this as a separate test rather than adding a
+    // conditionally-compiled segment to multiple tests.
+    //
+    // Test scenarios...
+    // 1 - Print the first n lines
+    // 2 - Print all-but the last n lines
+    // 3 - Print all but the last n lines, large file.
+    let scene = TestScenario::new(util_name!());
+    let fixtures = &scene.fixtures;
+
+    // Test 1 - Print the first n lines
+    fixtures.write("f1", "a\nb\nc\n");
+    let file = fixtures.open("f1");
+    let mut file_shadow = file.try_clone().unwrap();
+    scene
+        .ucmd()
+        .args(&["-n", "1"])
+        .set_stdin(file)
+        .succeeds()
+        .stdout_only("a\n");
+    let mut bytes_remaining_in_stdin = vec![];
+    assert_eq!(
+        file_shadow
+            .read_to_end(&mut bytes_remaining_in_stdin)
+            .unwrap(),
+        4
+    );
+    assert_eq!(
+        String::from_utf8(bytes_remaining_in_stdin).unwrap(),
+        "b\nc\n"
+    );
+
+    // Test 2 - Print all-but the last n lines
+    fixtures.write("f2", "a\nb\nc\n");
+    let file = fixtures.open("f2");
+    let mut file_shadow = file.try_clone().unwrap();
+    scene
+        .ucmd()
+        .args(&["-n", "-1"])
+        .set_stdin(file)
+        .succeeds()
+        .stdout_only("a\nb\n");
+    let mut bytes_remaining_in_stdin = vec![];
+    assert_eq!(
+        file_shadow
+            .read_to_end(&mut bytes_remaining_in_stdin)
+            .unwrap(),
+        2
+    );
+    assert_eq!(String::from_utf8(bytes_remaining_in_stdin).unwrap(), "c\n");
+
+    // Test 3 - Print all but the last n lines, large input file.
+    // First, create all our fixtures.
+    let seq_20000_file_name = "seq_20000";
+    let seq_1000_file_name = "seq_1000";
+    let seq_1001_20000_file_name = "seq_1001_20000";
+    scene
+        .cmd("seq")
+        .arg("20000")
+        .set_stdout(fixtures.make_file(seq_20000_file_name))
+        .succeeds();
+    scene
+        .cmd("seq")
+        .arg("1000")
+        .set_stdout(fixtures.make_file(seq_1000_file_name))
+        .succeeds();
+    scene
+        .cmd("seq")
+        .args(&["1001", "20000"])
+        .set_stdout(fixtures.make_file(seq_1001_20000_file_name))
+        .succeeds();
+
+    let file = fixtures.open(seq_20000_file_name);
+    let file_shadow = file.try_clone().unwrap();
+    scene
+        .ucmd()
+        .args(&["-n", "-19000"])
+        .set_stdin(file)
+        .succeeds()
+        .stdout_only_fixture(seq_1000_file_name);
+    scene
+        .cmd("cat")
+        .set_stdin(file_shadow)
+        .succeeds()
+        .stdout_only_fixture(seq_1001_20000_file_name);
+}
+
+#[cfg(all(
+    not(target_os = "windows"),
+    not(target_os = "macos"),
+    not(target_os = "android"),
+    not(target_os = "freebsd"),
+    not(target_os = "openbsd")
+))]
+#[test]
+fn test_validate_stdin_offset_bytes() {
+    // A handful of unix-only tests to validate behavior when reading from stdin on a seekable
+    // file. GNU-compatibility requires that the stdin file be left such that if another
+    // process is invoked on the same stdin file after head has run, the subsequent file should
+    // start reading from the byte after the last byte printed by head.
+    // Since this is unix-only requirement, keep this as a separate test rather than adding a
+    // conditionally-compiled segment to multiple tests.
+    //
+    // Test scenarios...
+    // 1 - Print the first n bytes
+    // 2 - Print all-but the last n bytes
+    // 3 - Print all-but the last n bytes, with n=0 (i.e. print everything)
+    // 4 - Print all but the last n bytes, large file.
+    let scene = TestScenario::new(util_name!());
+    let fixtures = &scene.fixtures;
+
+    // Test 1 - Print the first n bytes
+    fixtures.write("f1", "abc\ndef\n");
+    let file = fixtures.open("f1");
+    let mut file_shadow = file.try_clone().unwrap();
+    scene
+        .ucmd()
+        .args(&["-c", "2"])
+        .set_stdin(file)
+        .succeeds()
+        .stdout_only("ab");
+    let mut bytes_remaining_in_stdin = vec![];
+    assert_eq!(
+        file_shadow
+            .read_to_end(&mut bytes_remaining_in_stdin)
+            .unwrap(),
+        6
+    );
+    assert_eq!(
+        String::from_utf8(bytes_remaining_in_stdin).unwrap(),
+        "c\ndef\n"
+    );
+
+    // Test 2 - Print all-but the last n bytes
+    fixtures.write("f2", "abc\ndef\n");
+    let file = fixtures.open("f2");
+    let mut file_shadow = file.try_clone().unwrap();
+    scene
+        .ucmd()
+        .args(&["-c", "-3"])
+        .set_stdin(file)
+        .succeeds()
+        .stdout_only("abc\nd");
+    let mut bytes_remaining_in_stdin = vec![];
+    assert_eq!(
+        file_shadow
+            .read_to_end(&mut bytes_remaining_in_stdin)
+            .unwrap(),
+        3
+    );
+    assert_eq!(String::from_utf8(bytes_remaining_in_stdin).unwrap(), "ef\n");
+
+    // Test 3 - Print all-but the last n bytes, n=0 (i.e. print everything)
+    fixtures.write("f3", "abc\ndef\n");
+    let file = fixtures.open("f3");
+    let mut file_shadow = file.try_clone().unwrap();
+    scene
+        .ucmd()
+        .args(&["-c", "-0"])
+        .set_stdin(file)
+        .succeeds()
+        .stdout_only("abc\ndef\n");
+    let mut bytes_remaining_in_stdin = vec![];
+    assert_eq!(
+        file_shadow
+            .read_to_end(&mut bytes_remaining_in_stdin)
+            .unwrap(),
+        0
+    );
+    assert_eq!(String::from_utf8(bytes_remaining_in_stdin).unwrap(), "");
+
+    // Test 4 - Print all but the last n bytes, large input file.
+    // First, create all our fixtures.
+    let seq_20000_file_name = "seq_20000";
+    let seq_19000_file_name = "seq_19000";
+    let seq_19001_20000_file_name = "seq_19001_20000";
+    scene
+        .cmd("seq")
+        .arg("20000")
+        .set_stdout(fixtures.make_file(seq_20000_file_name))
+        .succeeds();
+    scene
+        .cmd("seq")
+        .arg("19000")
+        .set_stdout(fixtures.make_file(seq_19000_file_name))
+        .succeeds();
+    scene
+        .cmd("seq")
+        .args(&["19001", "20000"])
+        .set_stdout(fixtures.make_file(seq_19001_20000_file_name))
+        .succeeds();
+
+    let file = fixtures.open(seq_20000_file_name);
+    let file_shadow = file.try_clone().unwrap();
+    let seq_19001_20000_file_length = fixtures
+        .open(seq_19001_20000_file_name)
+        .metadata()
+        .unwrap()
+        .len();
+    scene
+        .ucmd()
+        .args(&["-c", &format!("-{}", seq_19001_20000_file_length)])
+        .set_stdin(file)
+        .succeeds()
+        .stdout_only_fixture(seq_19000_file_name);
+    scene
+        .cmd("cat")
+        .set_stdin(file_shadow)
+        .succeeds()
+        .stdout_only_fixture(seq_19001_20000_file_name);
 }
 
 #[cfg(all(