--filter argument for split

src/uu/split/src/platform/mod.rs

@@ -0,0 +1,11 @@
+#[cfg(unix)]
+pub use self::unix::instantiate_current_writer;
+
+#[cfg(windows)]
+pub use self::windows::instantiate_current_writer;
+
+#[cfg(unix)]
+mod unix;
+
+#[cfg(windows)]
+mod windows;

src/uu/split/src/platform/unix.rs

@@ -0,0 +1,124 @@
+use std::env;
+use std::io::Write;
+use std::io::{BufWriter, Result};
+use std::process::{Child, Command, Stdio};
+/// A writer that writes to a shell_process' stdin
+///
+/// We use a shell process (not directy calling a sub-process) so we can forward the name of the
+/// corresponding output file (xaa, xab, xac… ). This is the way it was implemented in GNU split.
+struct FilterWriter {
+    /// Running shell process
+    shell_process: Child,
+}
+
+impl Write for FilterWriter {
+    fn write(&mut self, buf: &[u8]) -> Result<usize> {
+        self.shell_process
+            .stdin
+            .as_mut()
+            .expect("failed to get shell stdin")
+            .write(buf)
+    }
+    fn flush(&mut self) -> Result<()> {
+        self.shell_process
+            .stdin
+            .as_mut()
+            .expect("failed to get shell stdin")
+            .flush()
+    }
+}
+
+/// Have an environment variable set at a value during this lifetime
+struct WithEnvVarSet {
+    /// Env var key
+    _previous_var_key: String,
+    /// Previous value set to this key
+    _previous_var_value: std::result::Result<String, env::VarError>,
+}
+impl WithEnvVarSet {
+    /// Save previous value assigned to key, set key=value
+    fn new(key: &str, value: &str) -> WithEnvVarSet {
+        let previous_env_value = env::var(key);
+        env::set_var(key, value);
+        WithEnvVarSet {
+            _previous_var_key: String::from(key),
+            _previous_var_value: previous_env_value,
+        }
+    }
+}
+
+impl Drop for WithEnvVarSet {
+    /// Restore previous value now that this is being dropped by context
+    fn drop(&mut self) {
+        if let Ok(ref prev_value) = self._previous_var_value {
+            env::set_var(&self._previous_var_key, &prev_value);
+        } else {
+            env::remove_var(&self._previous_var_key)
+        }
+    }
+}
+impl FilterWriter {
+    /// Create a new filter running a command with $FILE pointing at the output name
+    ///
+    /// #Arguments
+    ///
+    /// * `command` - The shell command to execute
+    /// * `filepath` - Path of the output file (forwarded to command as $FILE)
+    fn new(command: &str, filepath: &str) -> FilterWriter {
+        // set $FILE, save previous value (if there was one)
+        let _with_env_var_set = WithEnvVarSet::new("FILE", &filepath);
+
+        let shell_process = Command::new(env::var("SHELL").unwrap_or("/bin/sh".to_owned()))
+            .arg("-c")
+            .arg(command)
+            .stdin(Stdio::piped())
+            .spawn()
+            .expect("Couldn't spawn filter command");
+
+        FilterWriter {
+            shell_process: shell_process,
+        }
+    }
+}
+
+impl Drop for FilterWriter {
+    /// flush stdin, close it and wait on `shell_process` before dropping self
+    fn drop(&mut self) {
+        {
+            // close stdin by dropping it
+            let _stdin = self.shell_process.stdin.as_mut();
+        }
+        let exit_status = self
+            .shell_process
+            .wait()
+            .expect("Couldn't wait for child process");
+        if let Some(return_code) = exit_status.code() {
+            if return_code != 0 {
+                crash!(1, "Shell process returned {}", return_code);
+            }
+        } else {
+            crash!(1, "Shell process terminated by signal")
+        }
+    }
+}
+
+/// Instantiate either a file writer or a "write to shell process's stdin" writer
+pub fn instantiate_current_writer(
+    filter: &Option<String>,
+    filename: &str,
+) -> BufWriter<Box<dyn Write>> {
+    match filter {
+        None => BufWriter::new(Box::new(
+            // write to the next file
+            std::fs::OpenOptions::new()
+                .write(true)
+                .create(true)
+                .open(std::path::Path::new(&filename))
+                .unwrap(),
+        ) as Box<dyn Write>),
+        Some(ref filter_command) => BufWriter::new(Box::new(
+            // spawn a shell command and write to it
+            FilterWriter::new(&filter_command, &filename),
+        ) as Box<dyn Write>),
+    }
+}

src/uu/split/src/platform/windows.rs

@@ -0,0 +1,19 @@
+use std::io::BufWriter;
+use std::io::Write;
+/// Get a file writer
+///
+/// Unlike the unix version of this function, this _always_ returns
+/// a file writer
+pub fn instantiate_current_writer(
+    _filter: &Option<String>,
+    filename: &str,
+) -> BufWriter<Box<dyn Write>> {
+    BufWriter::new(Box::new(
+        // write to the next file
+        std::fs::OpenOptions::new()
+            .write(true)
+            .create(true)
+            .open(std::path::Path::new(&filename))
+            .unwrap(),
+    ) as Box<dyn Write>)
+}

src/uu/split/src/split.rs

@@ -10,8 +10,11 @@
 #[macro_use]
 extern crate uucore;
 
+mod platform;
+
 use std::char;
-use std::fs::{File, OpenOptions};
+use std::env;
+use std::fs::File;
 use std::io::{stdin, stdout, BufRead, BufReader, BufWriter, Read, Write};
 use std::path::Path;
 
@@ -47,6 +50,12 @@ pub fn uumain(args: impl uucore::Args) -> i32 {
         "additional suffix to append to output file names",
         "SUFFIX",
     );
+    opts.optopt(
+        "",
+        "filter",
+        "write to shell COMMAND file name is $FILE (Currently not implemented for Windows)",
+        "COMMAND",
+    );
     opts.optopt("l", "lines", "put NUMBER lines per output file", "NUMBER");
     opts.optflag(
         "",
@@ -92,6 +101,7 @@ size is 1000, and default PREFIX is 'x'. With no INPUT, or when INPUT is
         suffix_length: 0,
         additional_suffix: "".to_owned(),
         input: "".to_owned(),
+        filter: None,
         strategy: "".to_owned(),
         strategy_param: "".to_owned(),
         verbose: false,
@@ -138,6 +148,14 @@ size is 1000, and default PREFIX is 'x'. With no INPUT, or when INPUT is
     settings.input = input;
     settings.prefix = prefix;
 
+    settings.filter = matches.opt_str("filter");
+
+    if settings.filter.is_some() && cfg!(windows) {
+        // see https://github.com/rust-lang/rust/issues/29494
+        show_error!("--filter is currently not supported in this platform");
+        exit!(-1);
+    }
+
     split(&settings)
 }
 
@@ -147,6 +165,8 @@ struct Settings {
     suffix_length: usize,
     additional_suffix: String,
     input: String,
+    /// When supplied, a shell command to output to instead of xaa, xab …
+    filter: Option<String>,
     strategy: String,
     strategy_param: String,
     verbose: bool,
@@ -323,7 +343,6 @@ fn split(settings: &Settings) -> i32 {
                 _ => {}
             }
         }
-
         if control.request_new_file {
             let mut filename = settings.prefix.clone();
             filename.push_str(
@@ -336,17 +355,9 @@ fn split(settings: &Settings) -> i32 {
             );
             filename.push_str(settings.additional_suffix.as_ref());
 
-            if fileno != 0 {
-                crash_if_err!(1, writer.flush());
-            }
+            crash_if_err!(1, writer.flush());
             fileno += 1;
-            writer = BufWriter::new(Box::new(
-                OpenOptions::new()
-                    .write(true)
-                    .create(true)
-                    .open(Path::new(&filename))
-                    .unwrap(),
-            ) as Box<dyn Write>);
+            writer = platform::instantiate_current_writer(&settings.filter, filename.as_str());
             control.request_new_file = false;
             if settings.verbose {
                 println!("creating file '{}'", filename);

tests/by-util/test_split.rs

@@ -4,6 +4,8 @@ extern crate regex;
 use self::rand::{thread_rng, Rng};
 use self::regex::Regex;
 use crate::common::util::*;
+#[cfg(not(windows))]
+use std::env;
 use std::fs::{read_dir, File};
 use std::io::Write;
 use std::path::Path;
@@ -32,6 +34,7 @@ impl Glob {
         self.collect().len()
     }
 
+    /// Get all files in `self.directory` that match `self.regex`
     fn collect(&self) -> Vec<String> {
         read_dir(Path::new(&self.directory.subdir))
             .unwrap()
@@ -49,6 +52,7 @@ impl Glob {
             .collect()
     }
 
+    /// Accumulate bytes of all files in `self.collect()`
     fn collate(&self) -> Vec<u8> {
         let mut files = self.collect();
         files.sort();
@@ -60,11 +64,16 @@ impl Glob {
     }
 }
 
+/// File handle that user can add random bytes (line-formatted or not) to
 struct RandomFile {
     inner: File,
 }
 
 impl RandomFile {
+    /// Size of each line that's being generated
+    const LINESIZE: usize = 32;
+
+    /// `create()` file handle located at `at` / `name`
     fn new(at: &AtPath, name: &str) -> RandomFile {
         RandomFile {
             inner: File::create(&at.plus(name)).unwrap(),
@@ -81,11 +90,11 @@ impl RandomFile {
         let _ = write!(self.inner, "{}", random_chars(n));
     }
 
+    /// Add n lines each of size `RandomFile::LINESIZE`
     fn add_lines(&mut self, lines: usize) {
-        let line_size: usize = 32;
         let mut n = lines;
         while n > 0 {
-            let _ = writeln!(self.inner, "{}", random_chars(line_size));
+            let _ = writeln!(self.inner, "{}", random_chars(RandomFile::LINESIZE));
             n -= 1;
         }
     }
@@ -156,3 +165,64 @@ fn test_split_additional_suffix() {
     assert_eq!(glob.count(), 2);
     assert_eq!(glob.collate(), at.read(name).into_bytes());
 }
+
+// note: the test_filter* tests below are unix-only
+// windows support has been waived for now because of the difficulty of getting
+// the `cmd` call right
+// see https://github.com/rust-lang/rust/issues/29494
+
+#[test]
+#[cfg(unix)]
+fn test_filter() {
+    // like `test_split_default()` but run a command before writing
+    let (at, mut ucmd) = at_and_ucmd!();
+    let name = "filtered";
+    let glob = Glob::new(&at, ".", r"x[[:alpha:]][[:alpha:]]$");
+    let n_lines = 3;
+    RandomFile::new(&at, name).add_lines(n_lines);
+
+    // change all characters to 'i'
+    ucmd.args(&["--filter=sed s/./i/g > $FILE", name])
+        .succeeds();
+    // assert all characters are 'i' / no character is not 'i'
+    // (assert that command succeded)
+    assert!(
+        glob.collate().iter().find(|&&c| {
+            // is not i
+            c != ('i' as u8)
+            // is not newline
+            && c != ('\n' as u8)
+        }) == None
+    );
+}
+
+#[test]
+#[cfg(unix)]
+fn test_filter_with_env_var_set() {
+    // This test will ensure that if $FILE env var was set before running --filter, it'll stay that
+    // way
+    // implemented like `test_split_default()` but run a command before writing
+    let (at, mut ucmd) = at_and_ucmd!();
+    let name = "filtered";
+    let glob = Glob::new(&at, ".", r"x[[:alpha:]][[:alpha:]]$");
+    let n_lines = 3;
+    RandomFile::new(&at, name).add_lines(n_lines);
+
+    let env_var_value = "somevalue";
+    env::set_var("FILE", &env_var_value);
+    ucmd.args(&[format!("--filter={}", "cat > $FILE").as_str(), name])
+        .succeeds();
+    assert_eq!(glob.collate(), at.read(name).into_bytes());
+    assert!(env::var("FILE").unwrap_or("var was unset".to_owned()) == env_var_value);
+}
+
+#[test]
+#[cfg(unix)]
+fn test_filter_command_fails() {
+    let (at, mut ucmd) = at_and_ucmd!();
+    let name = "filter-will-fail";
+    RandomFile::new(&at, name).add_lines(4);
+
+    ucmd.args(&["--filter=/a/path/that/totally/does/not/exist", name])
+        .fails();
+}

tests/common/util.rs

@@ -72,8 +72,12 @@ pub fn repeat_str(s: &str, n: u32) -> String {
 pub struct CmdResult {
     //tmpd is used for convenience functions for asserts against fixtures
     tmpd: Option<Rc<TempDir>>,
+    /// zero-exit from running the Command?
+    /// see [`success`]
     pub success: bool,
+    /// captured utf-8 standard output after running the Command
     pub stdout: String,
+    /// captured utf-8 standard error after running the Command
     pub stderr: String,
 }