增加 perror 说明.

Signed-off-by: rick.chan <chenyang@autoai.com>

Software/Development/Language/C/C_Standard_Library/C_标准库实用说明.md

@@ -8,3 +8,31 @@
  */
 #include <stddef.h>
 ```
+
+## 2.stdlib 库
+
+## 2.1.perror
+
+**头文件：**
+
+```cpp
+#include <stdlib.h>
+```
+
+**函数原型：**
+
+```cpp
+void perror(const char *s);
+```
+
+**说明：**
+
+The perror() function produces a message on standard error describing the last error encountered during a call to a system or library function.
+
+**参数：**
+
+s：First (if s is not NULL and *s is not a null byte ('\0')), the argument string s is printed, followed by a colon and a blank.  Then an error message corresponding to the current value of errno and a new-line. To be of most use, the argument string should include the name of the function that incurred the error.
+
+**返回值：**
+
+无。