Don’t try reading from pipes or special file descriptors

CHANGELOG.md

@@ -24,6 +24,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Canonicalization: combine `text-*` and `leading-*` classes ([#19396](https://github.com/tailwindlabs/tailwindcss/pull/19396))
 - Correctly handle duplicate CLI arguments ([#19416](https://github.com/tailwindlabs/tailwindcss/pull/19416))
 - Don’t emit color-mix fallback rules inside `@keyframes` ([#19419](https://github.com/tailwindlabs/tailwindcss/pull/19419))
+- CLI: Don't hang when output is `/dev/stdout` ([#19421](https://github.com/tailwindlabs/tailwindcss/pull/19421))
 
 ### Added
 

packages/@tailwindcss-cli/src/commands/build/utils.ts

@@ -13,10 +13,19 @@ export function drainStdin() {
 }
 
 export async function outputFile(file: string, contents: string) {
-  try {
-    let currentContents = await fs.readFile(file, 'utf8')
-    if (currentContents === contents) return // Skip writing the file
-  } catch {}
+  // Check for special files like `/dev/stdout` or pipes. We don't want to read from these as that
+  // will hang the process until the file descriptors are closed.
+  let isSpecialFile = await fs
+    .stat(file)
+    .then((stats) => stats.isCharacterDevice() || stats.isFIFO())
+    .catch(() => false)
+
+  if (!isSpecialFile) {
+    try {
+      let currentContents = await fs.readFile(file, 'utf8')
+      if (currentContents === contents) return // Skip writing the file
+    } catch {}
+  }
 
   // Ensure the parent directories exist
   await fs.mkdir(path.dirname(file), { recursive: true })