# lv_log.h (/api/public/logging/lv_log_h)
Functions [#functions]
lv_log_register_print_cb [#lv_log_register_print_cb]
Register custom print/write function to call when a log is added. It can format its "File path", "Line number" and "Description" as required and send the formatted log message to a console or serial port.
```c title=" " lineNumbers=1
void lv_log_register_print_cb(lv_log_print_g_cb_t print_cb)
```
Parameters
| Name | Type | Description |
| ---------- | -------------------------------------- | --------------------------------- |
| `print_cb` | | a function pointer to print a log |
lv_log [#lv_log]
Print a log message via `printf` if enabled with `LV_LOG_PRINTF` in `lv_conf.h` and/or a print callback if registered with `lv_log_register_print_cb`
```c title=" " lineNumbers=1
void lv_log(const char *format,...)
```
Parameters
| Name | Type | Description |
| -------- | -------------- | ------------------------- |
| `format` | `const char *` | printf-like format string |
| `...` | | |
lv_log_add [#lv_log_add]
Add a log
```c title=" " lineNumbers=1
void lv_log_add(lv_log_level_t level, const char *file, int line, const char *func, const char *format,...)
```
Parameters
| Name | Type | Description |
| -------- | --------------------------------- | -------------------------------------------------- |
| `level` | | the level of log. (From `lv_log_level_t` enum) |
| `file` | `const char *` | name of the file when the log added |
| `line` | `int` | line number in the source code where the log added |
| `func` | `const char *` | name of the function when the log added |
| `format` | `const char *` | printf-like format string |
| `...` | | |
Typedefs [#typedefs]
lv_log_level_t [#lv_log_level_t]
```c title=" " lineNumbers=1
typedef int8_t lv_log_level_t
```
* `lv_log_add` — param `level`
lv_log_print_g_cb_t [#lv_log_print_g_cb_t]
```c title=" " lineNumbers=1
typedef void(* lv_log_print_g_cb_t) (lv_log_level_t level, const char *buf)
```
Log print function. Receives a string buffer to print".
* `lv_log_register_print_cb` — param `print_cb`
Macros [#macros]
LV_LOG_FILE [#lv_log_file]
```c title=" " lineNumbers=1
#define LV_LOG_FILE __FILE__
```
LV_LOG_LINE [#lv_log_line]
```c title=" " lineNumbers=1
#define LV_LOG_LINE __LINE__
```
LV_LOG_TRACE [#lv_log_trace]
```c title=" " lineNumbers=1
#define LV_LOG_TRACE(...) \
do {}while(0)
```
LV_LOG_INFO [#lv_log_info]
```c title=" " lineNumbers=1
#define LV_LOG_INFO(...) \
do {}while(0)
```
LV_LOG_WARN [#lv_log_warn]
```c title=" " lineNumbers=1
#define LV_LOG_WARN(...) \
lv_log_add(LV_LOG_LEVEL_WARN, LV_LOG_FILE, LV_LOG_LINE, __func__, __VA_ARGS__)
```
LV_LOG_WARN_ONCE [#lv_log_warn_once]
```c title=" " lineNumbers=1
#define LV_LOG_WARN_ONCE(...) \
do { \
static int warned = 0; \
if(!warned) { \
warned = 1; \
lv_log_add(LV_LOG_LEVEL_WARN, LV_LOG_FILE, LV_LOG_LINE, __func__, __VA_ARGS__); \
} \
} while(0)
```
LV_LOG_DEPRECATED [#lv_log_deprecated]
```c title=" " lineNumbers=1
#define LV_LOG_DEPRECATED(msg) \
LV_LOG_WARN_ONCE("Deprecated: " msg)
```
LV_LOG_ERROR [#lv_log_error]
```c title=" " lineNumbers=1
#define LV_LOG_ERROR(...) \
lv_log_add(LV_LOG_LEVEL_ERROR, LV_LOG_FILE, LV_LOG_LINE, __func__, __VA_ARGS__)
```
LV_LOG_USER [#lv_log_user]
```c title=" " lineNumbers=1
#define LV_LOG_USER(...) \
lv_log_add(LV_LOG_LEVEL_USER, LV_LOG_FILE, LV_LOG_LINE, __func__, __VA_ARGS__)
```
LV_LOG [#lv_log-1]
```c title=" " lineNumbers=1
#define LV_LOG(...) \
lv_log(__VA_ARGS__)
```
Dependencies [#dependencies]