child_process: truncate output when maxBuffer is exceeded

Preserves truncated output for `child_process.exec()` when `maxBuffer`
is exceeded.

This is particularly useful for commands which have indistinguishable
error codes for what output they produce.

PR-URL: https://github.com/nodejs/node/pull/24951
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Anna Henningsen <anna@addaleax.net>

1 files changed, 12 insertions, 8 deletions

diff --git a/doc/api/child_process.md b/doc/api/child_process.md
index e32568cd78..cdfdab1a98 100644
--- a/doc/api/child_process.md
+++ b/doc/api/child_process.md
@@ -147,8 +147,9 @@ changes:
     `'/bin/sh'` on UNIX, `process.env.ComSpec` on Windows.
   * `timeout` {number} **Default:** `0`
   * `maxBuffer` {number} Largest amount of data in bytes allowed on stdout or
-    stderr. If exceeded, the child process is terminated. See caveat at
-    [`maxBuffer` and Unicode][]. **Default:** `200 * 1024`.
+    stderr. If exceeded, the child process is terminated and any output is
+    truncated. See caveat at [`maxBuffer` and Unicode][].
+    **Default:** `200 * 1024`.
   * `killSignal` {string|integer} **Default:** `'SIGTERM'`
   * `uid` {number} Sets the user identity of the process (see setuid(2)).
   * `gid` {number} Sets the group identity of the process (see setgid(2)).
@@ -245,8 +246,9 @@ changes:
   * `encoding` {string} **Default:** `'utf8'`
   * `timeout` {number} **Default:** `0`
   * `maxBuffer` {number} Largest amount of data in bytes allowed on stdout or
-    stderr. If exceeded, the child process is terminated. See caveat at
-    [`maxBuffer` and Unicode][]. **Default:** `200 * 1024`.
+    stderr. If exceeded, the child process is terminated and any output is
+    truncated. See caveat at [`maxBuffer` and Unicode][].
+    **Default:** `200 * 1024`.
   * `killSignal` {string|integer} **Default:** `'SIGTERM'`
   * `uid` {number} Sets the user identity of the process (see setuid(2)).
   * `gid` {number} Sets the group identity of the process (see setgid(2)).
@@ -779,8 +781,9 @@ changes:
   * `killSignal` {string|integer} The signal value to be used when the spawned
     process will be killed. **Default:** `'SIGTERM'`.
   * `maxBuffer` {number} Largest amount of data in bytes allowed on stdout or
-    stderr. If exceeded, the child process is terminated. See caveat at
-    [`maxBuffer` and Unicode][]. **Default:** `200 * 1024`.
+    stderr. If exceeded, the child process is terminated and any output is
+    truncated. See caveat at [`maxBuffer` and Unicode][].
+    **Default:** `200 * 1024`.
   * `encoding` {string} The encoding used for all stdio inputs and outputs.
     **Default:** `'buffer'`.
   * `windowsHide` {boolean} Hide the subprocess console window that would
@@ -842,8 +845,9 @@ changes:
   * `killSignal` {string|integer} The signal value to be used when the spawned
     process will be killed. **Default:** `'SIGTERM'`.
   * `maxBuffer` {number} Largest amount of data in bytes allowed on stdout or
-    stderr. If exceeded, the child process is terminated. See caveat at
-    [`maxBuffer` and Unicode][]. **Default:** `200 * 1024`.
+    stderr. If exceeded, the child process is terminated and any output is
+    truncated. See caveat at [`maxBuffer` and Unicode][].
+    **Default:** `200 * 1024`.
   * `encoding` {string} The encoding used for all stdio inputs and outputs.
     **Default:** `'buffer'`.
   * `shell` {boolean|string} If `true`, runs `command` inside of a shell. Uses