make nbsh -c work

2 files changed, 42 insertions, 26 deletions

diff --git a/src/main.rs b/src/main.rs
index b65fb1e..48d2b2b 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -24,17 +24,41 @@ mod prelude;
 mod runner;
 mod shell;
 
-async fn async_main() -> anyhow::Result<i32> {
+use prelude::*;
+
+async fn async_main(
+    shell_write: Option<&async_std::fs::File>,
+) -> anyhow::Result<i32> {
     if std::env::args().nth(1).as_deref() == Some("-c") {
-        return runner::run(std::env::args().nth(2).as_deref().unwrap())
-            .await;
+        return runner::run(
+            std::env::args().nth(2).as_deref().unwrap(),
+            shell_write,
+        )
+        .await;
     }
 
     shell::main().await
 }
 
 fn main() {
-    match async_std::task::block_on(async_main()) {
+    // need to do this here because the async-std executor allocates some fds,
+    // and so in the case where we aren't being called from the main shell and
+    // fd 3 wasn't preallocated in advance, we need to be able to tell that
+    // before async-std opens something on fd 3
+    let shell_write = if nix::sys::stat::fstat(3).is_ok() {
+        nix::fcntl::fcntl(
+            3,
+            nix::fcntl::FcntlArg::F_SETFD(nix::fcntl::FdFlag::FD_CLOEXEC),
+        )
+        .unwrap();
+        // Safety: we don't create File instances for or read/write data on fd
+        // 3 anywhere else
+        Some(unsafe { async_std::fs::File::from_raw_fd(3) })
+    } else {
+        None
+    };
+
+    match async_std::task::block_on(async_main(shell_write.as_ref())) {
         Ok(code) => {
             std::process::exit(code);
         }
diff --git a/src/runner/mod.rs b/src/runner/mod.rs
index 0f02ef0..98894b3 100644
--- a/src/runner/mod.rs
+++ b/src/runner/mod.rs
@@ -69,16 +69,14 @@ enum Frame {
     For(bool, usize, Vec<String>),
 }
 
-pub async fn run(commands: &str) -> anyhow::Result<i32> {
-    // Safety: we don't create File instances for or read/write data on fd
-    // 3 anywhere else
-    let shell_write = unsafe { async_std::fs::File::from_raw_fd(3) };
-    cloexec(3)?;
-
+pub async fn run(
+    commands: &str,
+    shell_write: Option<&async_std::fs::File>,
+) -> anyhow::Result<i32> {
     let mut env = Env::new_from_env()?;
-    run_commands(commands, &mut env, &shell_write).await?;
+    run_commands(commands, &mut env, shell_write).await?;
     let status = env.latest_status();
-    write_event(&shell_write, Event::Exit(env)).await?;
+    write_event(shell_write, Event::Exit(env)).await?;
 
     if let Some(signal) = status.signal() {
         nix::sys::signal::raise(signal.try_into().unwrap())?;
@@ -89,7 +87,7 @@ pub async fn run(commands: &str) -> anyhow::Result<i32> {
 async fn run_commands(
     commands: &str,
     env: &mut Env,
-    shell_write: &async_std::fs::File,
+    shell_write: Option<&async_std::fs::File>,
 ) -> anyhow::Result<()> {
     let commands = crate::parse::ast::Commands::parse(commands)?;
     let commands = commands.commands();
@@ -194,7 +192,7 @@ async fn run_commands(
 async fn run_pipeline(
     pipeline: crate::parse::ast::Pipeline,
     env: &mut Env,
-    shell_write: &async_std::fs::File,
+    shell_write: Option<&async_std::fs::File>,
 ) -> anyhow::Result<()> {
     write_event(shell_write, Event::RunPipeline(env.idx(), pipeline.span()))
         .await?;
@@ -224,11 +222,13 @@ async fn run_pipeline(
 }
 
 async fn write_event(
-    mut fh: &async_std::fs::File,
+    fh: Option<&async_std::fs::File>,
     event: Event,
 ) -> anyhow::Result<()> {
-    fh.write_all(&bincode::serialize(&event)?).await?;
-    fh.flush().await?;
+    if let Some(mut fh) = fh {
+        fh.write_all(&bincode::serialize(&event)?).await?;
+        fh.flush().await?;
+    }
     Ok(())
 }
 
@@ -277,7 +277,7 @@ async fn wait_children(
     pg: Option<nix::unistd::Pid>,
     env: &Env,
     io: &builtins::Io,
-    shell_write: &async_std::fs::File,
+    shell_write: Option<&async_std::fs::File>,
 ) -> std::process::ExitStatus {
     enum Res {
         Child(nix::Result<nix::sys::wait::WaitStatus>),
@@ -514,14 +514,6 @@ fn setpgid_parent(
     Ok(())
 }
 
-fn cloexec(fd: std::os::unix::io::RawFd) -> anyhow::Result<()> {
-    nix::fcntl::fcntl(
-        fd,
-        nix::fcntl::FcntlArg::F_SETFD(nix::fcntl::FdFlag::FD_CLOEXEC),
-    )?;
-    Ok(())
-}
-
 fn id_to_pid(id: u32) -> nix::unistd::Pid {
     nix::unistd::Pid::from_raw(id.try_into().unwrap())
 }