From e6f0af31a70b10709bd20acabbcb634874d0534d Mon Sep 17 00:00:00 2001
From: ecsimsw <ecsimsw@gmail.com>
Date: Thu, 9 Jul 2026 18:51:22 +0900
Subject: [PATCH 1/8] feat(file-logger): use io.stdout/io.stderr for
 /dev/stdout and /dev/stderr paths

---
 apisix/plugins/file-logger.lua | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/apisix/plugins/file-logger.lua b/apisix/plugins/file-logger.lua
index afe73d662b79..9d7403502f36 100644
--- a/apisix/plugins/file-logger.lua
+++ b/apisix/plugins/file-logger.lua
@@ -21,6 +21,8 @@ local plugin       =   require("apisix.plugin")
 local expr         =   require("resty.expr.v1")
 local ngx          =   ngx
 local io_open      =   io.open
+local io_stdout    =   io.stdout
+local io_stderr    =   io.stderr
 local is_apisix_or, process = pcall(require, "resty.apisix.process")
 
 
@@ -89,6 +91,12 @@ local _M = {
 }
 
 
+local std_files = {
+    ["/dev/stdout"] = io_stdout,
+    ["/dev/stderr"] = io_stderr,
+}
+
+
 local function get_configured_path(conf)
     if conf.path then
         return conf.path
@@ -152,6 +160,11 @@ if is_apisix_or then
     end
 
     function open_file_cache(conf)
+        local std_file = std_files[conf.path]
+        if std_file then
+            return std_file
+        end
+
         local last_reopen_time = process.get_last_reopen_ms()
 
         local handler, err = path_to_file(conf.path, 0, open_file_handler, conf, {})
@@ -185,7 +198,10 @@ local function write_file_data(conf, log_message)
 
     local file, err
     local file_conf = conf.path and conf or {path = path}
-    if open_file_cache then
+    local std_file = std_files[path]
+    if std_file then
+        file = std_file
+    elseif open_file_cache then
         file, err = open_file_cache(file_conf)
     else
         file, err = io_open(path, 'a+')
@@ -204,8 +220,9 @@ local function write_file_data(conf, log_message)
             core.log.error("failed to write file: ", path, ", error info: ", err)
         end
 
+        -- stdout/stderr should not be closed
         -- file will be closed by gc, if open_file_cache exists
-        if not open_file_cache then
+        if not open_file_cache and not std_file then
             file:close()
         end
     end

From 090afa30b4e1f253468155aab3c50e495a676d7a Mon Sep 17 00:00:00 2001
From: ecsimsw <ecsimsw@gmail.com>
Date: Thu, 9 Jul 2026 20:12:37 +0900
Subject: [PATCH 2/8] feat(file-logger): disable buffering for stdout/stderr
 handles

---
 apisix/plugins/file-logger.lua | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/apisix/plugins/file-logger.lua b/apisix/plugins/file-logger.lua
index 9d7403502f36..d14ecd61966c 100644
--- a/apisix/plugins/file-logger.lua
+++ b/apisix/plugins/file-logger.lua
@@ -95,6 +95,8 @@ local std_files = {
     ["/dev/stdout"] = io_stdout,
     ["/dev/stderr"] = io_stderr,
 }
+io_stdout:setvbuf("no")
+io_stderr:setvbuf("no")
 
 
 local function get_configured_path(conf)

From 9bb47d1210abc32c16bff3cd5fa6455aaf3de2cd Mon Sep 17 00:00:00 2001
From: ecsimsw <ecsimsw@gmail.com>
Date: Thu, 9 Jul 2026 20:12:48 +0900
Subject: [PATCH 3/8] test(file-logger): add cli test for stdout/stderr output

---
 t/cli/test_file_logger_stdout.sh | 67 ++++++++++++++++++++++++++++++++
 1 file changed, 67 insertions(+)
 create mode 100755 t/cli/test_file_logger_stdout.sh

diff --git a/t/cli/test_file_logger_stdout.sh b/t/cli/test_file_logger_stdout.sh
new file mode 100755
index 000000000000..6b2271ad9c10
--- /dev/null
+++ b/t/cli/test_file_logger_stdout.sh
@@ -0,0 +1,67 @@
+#!/usr/bin/env bash
+
+#
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements.  See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.
+# The ASF licenses this file to You under the Apache License, Version 2.0
+# (the "License"); you may not use this file except in compliance with
+# the License.  You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+. ./t/cli/common.sh
+
+# file-logger: write to stdout via /dev/stdout
+
+echo '
+apisix:
+  node_listen: 9080
+deployment:
+  role: data_plane
+  role_data_plane:
+    config_provider: yaml
+nginx_config:
+  main_configuration_snippet: |
+    daemon off;
+' > conf/config.yaml
+
+echo '
+routes:
+  - uri: /hello
+    upstream:
+      nodes:
+        "127.0.0.1:1980": 1
+      type: roundrobin
+    plugins:
+      file-logger:
+        path: /dev/stdout
+#END
+' > conf/apisix.yaml
+
+make init
+
+./bin/apisix start > stdout.log 2>&1 &
+apisix_pid=$!
+sleep 1
+
+curl -s http://127.0.0.1:9080/hello > /dev/null
+sleep 2
+
+kill "$apisix_pid" 2>/dev/null || true
+wait "$apisix_pid" 2>/dev/null || true
+
+if ! grep -q "uri.*hello" stdout.log; then
+    echo "failed: file-logger did not write to stdout"
+    cat stdout.log
+    exit 1
+fi
+
+echo "passed: file-logger stdout support"

From 5d971f712181450f281e864cbdd34f773116d9f4 Mon Sep 17 00:00:00 2001
From: ecsimsw <ecsimsw@gmail.com>
Date: Thu, 9 Jul 2026 20:52:43 +0900
Subject: [PATCH 4/8] docs(file-logger): document /dev/stdout and /dev/stderr
 path support

---
 docs/en/latest/plugins/file-logger.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/docs/en/latest/plugins/file-logger.md b/docs/en/latest/plugins/file-logger.md
index 183ee55b6268..92b6ee0388e3 100644
--- a/docs/en/latest/plugins/file-logger.md
+++ b/docs/en/latest/plugins/file-logger.md
@@ -45,7 +45,7 @@ The `file-logger` Plugin is used to push log streams to a specific location.
 
 | Name | Type   | Required | Description   |
 | ---- | ------ | -------- | ------------- |
-| path | string | True     | Log file path. |
+| path | string | True     | Log file path. You can use `/dev/stdout` to write logs to the standard output and `/dev/stderr` to write to the standard error output. |
 | log_format | object | False    | Log format declared as key-value pairs in JSON. Values support strings and nested objects (up to five levels deep; deeper fields are truncated). Within strings, [APISIX](../apisix-variable.md) or [NGINX](http://nginx.org/en/docs/varindex.html) variables can be referenced by prefixing with `$`. |
 | include_req_body       | boolean | False    | When set to `true` includes the request body in the log. If the request body is too big to be kept in the memory, it can't be logged due to Nginx's limitations. |
 | include_req_body_expr  | array   | False    | Filter for when the `include_req_body` attribute is set to `true`. Request body is only logged when the expression set here evaluates to `true`. See [lua-resty-expr](https://github.com/api7/lua-resty-expr) for more. |

From be06a9263ec247fd4f914995bd8a79467d7bf833 Mon Sep 17 00:00:00 2001
From: ecsimsw <ecsimsw@gmail.com>
Date: Thu, 16 Jul 2026 21:54:02 +0900
Subject: [PATCH 5/8] refactor(file-logger): remove redundant std_file lookup
 in open_file_cache

std_files is already resolved before open_file_cache is called, so the
branch inside open_file_cache was dead code.
---
 apisix/plugins/file-logger.lua | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/apisix/plugins/file-logger.lua b/apisix/plugins/file-logger.lua
index d14ecd61966c..f7201f5337d7 100644
--- a/apisix/plugins/file-logger.lua
+++ b/apisix/plugins/file-logger.lua
@@ -162,11 +162,6 @@ if is_apisix_or then
     end
 
     function open_file_cache(conf)
-        local std_file = std_files[conf.path]
-        if std_file then
-            return std_file
-        end
-
         local last_reopen_time = process.get_last_reopen_ms()
 
         local handler, err = path_to_file(conf.path, 0, open_file_handler, conf, {})

From c959f3a7921a690e8b3fc078448e4f61c956c6ae Mon Sep 17 00:00:00 2001
From: ecsimsw <ecsimsw@gmail.com>
Date: Thu, 16 Jul 2026 21:54:02 +0900
Subject: [PATCH 6/8] test(file-logger): capture process stdout by running
 openresty directly

`apisix start` launches nginx via io.popen and consumes its stdout, so it
cannot observe /dev/stdout output. Run openresty in the foreground like the
container entrypoint does, and wait for readiness instead of a fixed sleep.
---
 t/cli/test_file_logger_stdout.sh | 32 +++++++++++++++++++++++---------
 1 file changed, 23 insertions(+), 9 deletions(-)

diff --git a/t/cli/test_file_logger_stdout.sh b/t/cli/test_file_logger_stdout.sh
index 6b2271ad9c10..42946c26e47b 100755
--- a/t/cli/test_file_logger_stdout.sh
+++ b/t/cli/test_file_logger_stdout.sh
@@ -19,7 +19,13 @@
 
 . ./t/cli/common.sh
 
-# file-logger: write to stdout via /dev/stdout
+# file-logger: verify logs are written to the standard output via "/dev/stdout".
+#
+# APISIX in a container runs openresty directly in the foreground
+# (see docker/debian-dev/docker-entrypoint.sh: `openresty -p ... -g 'daemon off;'`),
+# so its stdout is the container's stdout. We replicate that here to capture
+# the process stdout. (`apisix start` launches nginx via io.popen and consumes
+# its stdout, so it cannot be used to observe /dev/stdout output.)
 
 echo '
 apisix:
@@ -28,9 +34,6 @@ deployment:
   role: data_plane
   role_data_plane:
     config_provider: yaml
-nginx_config:
-  main_configuration_snippet: |
-    daemon off;
 ' > conf/config.yaml
 
 echo '
@@ -47,21 +50,32 @@ routes:
 ' > conf/apisix.yaml
 
 make init
+# `apisix start` would create the logs directory; since we launch openresty
+# directly, create it ourselves so nginx can open its error log.
+mkdir -p logs
 
-./bin/apisix start > stdout.log 2>&1 &
+# run openresty directly in the foreground and capture its stdout
+openresty -p "$PWD" -g 'daemon off;' > stdout.log 2> stderr.log &
 apisix_pid=$!
-sleep 1
+
+# wait until APISIX is ready to serve
+for _ in $(seq 1 20); do
+    if curl -s -o /dev/null http://127.0.0.1:9080/hello; then
+        break
+    fi
+    sleep 0.5
+done
 
 curl -s http://127.0.0.1:9080/hello > /dev/null
-sleep 2
+sleep 1
 
 kill "$apisix_pid" 2>/dev/null || true
 wait "$apisix_pid" 2>/dev/null || true
 
-if ! grep -q "uri.*hello" stdout.log; then
+if ! grep -q '"uri":"/hello"' stdout.log; then
     echo "failed: file-logger did not write to stdout"
     cat stdout.log
     exit 1
 fi
 
-echo "passed: file-logger stdout support"
+echo "passed: file-logger writes to stdout"

From d62672fc0010af4264aeed42811fb4077fb74d0b Mon Sep 17 00:00:00 2001
From: ecsimsw <ecsimsw@gmail.com>
Date: Thu, 16 Jul 2026 21:54:02 +0900
Subject: [PATCH 7/8] docs(file-logger): document /dev/stdout and /dev/stderr
 path support in zh

---
 docs/zh/latest/plugins/file-logger.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/docs/zh/latest/plugins/file-logger.md b/docs/zh/latest/plugins/file-logger.md
index 3509b697ffcc..a128e574bfe2 100644
--- a/docs/zh/latest/plugins/file-logger.md
+++ b/docs/zh/latest/plugins/file-logger.md
@@ -47,7 +47,7 @@ description: API 网关 Apache APISIX file-logger 插件可用于将日志数据
 
 | 名称             | 类型     | 必选项 | 描述                                             |
 | ---------------- | ------- |-----| ------------------------------------------------ |
-| path             | string  | 是   | 自定义输出文件路径。例如：`logs/file.log`。        |
+| path             | string  | 是   | 自定义输出文件路径。例如：`logs/file.log`。可以使用 `/dev/stdout` 将日志写入标准输出，使用 `/dev/stderr` 将日志写入标准错误输出。 |
 | log_format       | object  | 否   | 日志格式以 JSON 的键值对声明。值支持字符串和嵌套对象（最多五层，超出部分将被截断）。字符串中可通过在前面加上 `$` 来引用 [APISIX 变量](../apisix-variable.md) 或 [NGINX 内置变量](http://nginx.org/en/docs/varindex.html)。 |
 | include_req_body   | boolean | 否   | 当设置为 `true` 时，日志中将包含请求体。如果请求体太大而无法在内存中保存，则由于 Nginx 的限制，无法记录请求体。|
 | include_req_body_expr | array   | 否   | 当 `include_req_body` 属性设置为 `true` 时的过滤器。只有当此处设置的表达式求值为 `true` 时，才会记录请求体。有关更多信息，请参阅 [lua-resty-expr](https://github.com/api7/lua-resty-expr) 。 |

From 6f9c542618f3841603ba0024120acd4c0fe2ff2c Mon Sep 17 00:00:00 2001
From: ecsimsw <ecsimsw@gmail.com>
Date: Thu, 16 Jul 2026 22:52:22 +0900
Subject: [PATCH 8/8] style(file-logger): shorten test comment to match project
 convention

---
 t/cli/test_file_logger_stdout.sh | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/t/cli/test_file_logger_stdout.sh b/t/cli/test_file_logger_stdout.sh
index 42946c26e47b..681c1237ed48 100755
--- a/t/cli/test_file_logger_stdout.sh
+++ b/t/cli/test_file_logger_stdout.sh
@@ -19,13 +19,9 @@
 
 . ./t/cli/common.sh
 
-# file-logger: verify logs are written to the standard output via "/dev/stdout".
-#
-# APISIX in a container runs openresty directly in the foreground
-# (see docker/debian-dev/docker-entrypoint.sh: `openresty -p ... -g 'daemon off;'`),
-# so its stdout is the container's stdout. We replicate that here to capture
-# the process stdout. (`apisix start` launches nginx via io.popen and consumes
-# its stdout, so it cannot be used to observe /dev/stdout output.)
+# file-logger: verify logs are written to stdout via "/dev/stdout".
+# Uses openresty directly (like docker-entrypoint.sh) because `apisix start`
+# consumes stdout via io.popen, making /dev/stdout output unobservable.
 
 echo '
 apisix: