doc,child_process: pid can be undefined when ENOENT

From the code `nodejs@8` and up should behave the same: github.com/nodejs/node/blame/v8.17.0/lib/internal/child_process.js#L290 And a short test snippet: ```js const { spawn } = require('child_process') const subProcess = spawn('non-exist-command') subProcess.on('error', (error) => console.warn('mute Unhandled "error" event:', error)) console.log('- pid:', subProcess.pid) process.nextTick(() => console.log('- after error emit')) console.log('== end of test ==') ``` Note: the sync spawn result `pid` currently do not follow this pattern. Co-authored-by: Rich Trott <rtrott@gmail.com> PR-URL: #37014 Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
nodejs · May 1, 2021 · a3c564bead0b8e3e71d635f259395b6165879124 · a3c564b
1 parent 605cb4c
commit a3c564bead0b8e3e71d635f259395b6165879124
Showing with 4 additions and 2 deletions.

+4 −2 doc/api/child_process.md
diff --git a/doc/api/child_process.md b/doc/api/child_process.md
@@ -1243,9 +1243,11 @@ does not indicate that the child process has been terminated.
 added: v0.1.90
 -->
 
-* {integer}
+* {integer|undefined}
 
-Returns the process identifier (PID) of the child process.
+Returns the process identifier (PID) of the child process. If the child process
+fails to spawn due to errors, then the value is `undefined` and `error` is
+emitted.
 
 ```js
 const { spawn } = require('child_process');