Flexi Logger

https://docs.rs/flexi_logger/latest/flexi_logger/
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Flexi Logger is a flexible and easy-to-use Rust logger that writes logs to stderr and/or files with...
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### init() - Quick Start Logger Initialization

Source: https://docs.rs/flexi_logger/latest/flexi_logger/fn.init.html

The `init()` function is the shortest way to get started with flexi_logger. It configures logging based on the `RUST_LOG` environment variable or defaults to 'info' level, and directs logs to stderr.

```APIDOC
## init()

### Description
Provides the shortest form to get started with flexi_logger. It configures logging based on the `RUST_LOG` environment variable or defaults to 'info' level, and directs logs to stderr.

### Method
`pub fn init()`

### Endpoint
N/A (This is a function call, not an HTTP endpoint)

### Parameters
None

### Request Body
None

### Request Example
```rust
flexi_logger::init();
```

### Response
None (This function initiates logging and does not return a value directly related to logging output).

### Equivalent Configuration
```rust
Logger::try_with_env_or_str("info")
   .unwrap_or_else(|_e| Logger::with(LogSpecification::info()))
   .log_to_stderr()
   .start()
   .ok();
```

### Notes
- Log specification can be configured via the environment variable `RUST_LOG`.
- If `RUST_LOG` is not set, the default log specification is `'info'`.
- Logs are written directly to `stderr` without buffering.
- The `LogHandle` returned by `Logger::start()` is implicitly dropped, which is acceptable for this configuration.
```

--------------------------------

### Example: Keep Log and Compressed Files

Source: https://docs.rs/flexi_logger/latest/flexi_logger/enum.Cleanup.html

This example demonstrates keeping the youngest five log files as text files and the next 30 as compressed files with a `.gz` suffix. Older files are removed. This variant is available when the `compress` crate feature is enabled.

```rust
KeepLogAndCompressedFiles(5,30)
```

--------------------------------

### Record Example

Source: https://docs.rs/flexi_logger/latest/flexi_logger/struct.Record.html

An example demonstrating how to implement the `log::Log` trait using the `Record` struct to display log messages.

```APIDOC
## Example
```rust
struct SimpleLogger;

impl log::Log for SimpleLogger {
   fn enabled(&self, _metadata: &log::Metadata) -> bool {
       true
   }

   fn log(&self, record: &log::Record) {
       if !self.enabled(record.metadata()) {
           return;
       }

       println!("{}:{} -- {}",
                record.level(),
                record.target(),
                record.args());
   }
   fn flush(&self) {}
}
```
```

--------------------------------

### Logger Initialization API

Source: https://docs.rs/flexi_logger/latest/flexi_logger/struct.Logger.html

This section covers the primary methods for starting and initializing the FlexiLogger.

```APIDOC
## POST /api/users

### Description
Consumes the Logger object and initializes `flexi_logger`. It's crucial to keep the `LoggerHandle` alive until the program terminates to ensure proper flushing and shutdown of log writers.

### Method
POST

### Endpoint
/start

### Parameters
#### Query Parameters
- **specfile** (string) - Optional - Path to a specfile for dynamic log specification updates.

### Request Body
This method does not explicitly define a request body in the provided documentation. Configuration is typically done via builder methods before calling `start`.

### Response
#### Success Response (200)
- **LoggerHandle** (object) - A handle to the logger, which must be kept alive.

#### Error Response (FlexiLoggerError)
- **FlexiLoggerError** (enum) - Various error types that can occur during logger initialization.

### Request Example
```rust
use flexi_logger::{Logger, WriteMode, FileSpec};

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let _logger = Logger::try_with_str("info")?
        .log_to_file(FileSpec::default())
        .write_mode(WriteMode::BufferAndFlush)
        .start()?;

    // ... program logic ...

    Ok(())
}
```
```

```APIDOC
## POST /api/users

### Description
Builds a boxed logger and a `LoggerHandle` without initializing the global logger. The returned logger can be installed manually or nested.

### Method
POST

### Endpoint
/build

### Parameters
#### Query Parameters
- **specfile** (string) - Optional - Path to a specfile for dynamic log specification updates.

### Request Body
This method does not explicitly define a request body. Configuration is typically done via builder methods before calling `build`.

### Response
#### Success Response (200)
- **(Box<dyn Log>, LoggerHandle)** - A tuple containing the boxed logger and a logger handle.

#### Error Response (FlexiLoggerError)
- **FlexiLoggerError** (enum) - Various error types that can occur during logger building.

### Request Example
```rust
use flexi_logger::Logger;

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let (logger, _handle) = Logger::try_with_str("info")?.build()?;
    // Use the logger manually or nest it
    Ok(())
}
```
```

```APIDOC
## POST /api/users

### Description
Initializes `flexi_logger` using a specfile, allowing the log specification to be updated programmatically while the program is running. If the specfile does not exist, it will be created with the initial specification.

### Method
POST

### Endpoint
/start_with_specfile

### Parameters
#### Path Parameters
- **specfile** (string) - Required - The path to the log specification file (e.g., `logspecification.toml`).

### Request Body
This method does not explicitly define a request body. Configuration is typically done via builder methods before calling `start_with_specfile`.

### Response
#### Success Response (200)
- **LoggerHandle** (object) - A handle to the logger, which must be kept alive.

#### Error Response (FlexiLoggerError)
- **FlexiLoggerError** (enum) - Various error types that can occur during logger initialization.

### Request Example
```rust
use flexi_logger::Logger;

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let _logger = Logger::try_with_str("info")?
        .start_with_specfile("logspecification.toml")?;

    // ... program logic ...

    Ok(())
}
```

### Specfile Example (`logspecification.toml`)
```toml
### Optional: Default log level
global_level = 'info'
### Optional: specify a regular expression to suppress all messages that don't match
#global_pattern = 'foo'

### Specific log levels per module are optionally defined in this section
[modules]
#'mod1' = 'warn'
#'mod2' = 'debug'
#'mod2::mod3' = 'trace'
```
```

```APIDOC
## POST /api/users

### Description
Builds a boxed logger and a `LoggerHandle` using a specfile, without initializing the global logger. This allows for manual installation or nesting of the logger.

### Method
POST

### Endpoint
/build_with_specfile

### Parameters
#### Path Parameters
- **specfile** (string) - Required - The path to the log specification file (e.g., `logspecification.toml`).

### Request Body
This method does not explicitly define a request body. Configuration is typically done via builder methods before calling `build_with_specfile`.

### Response
#### Success Response (200)
- **(Box<dyn Log>, LoggerHandle)** - A tuple containing the boxed logger and a logger handle.

#### Error Response (FlexiLoggerError)
- **FlexiLoggerError** (enum) - Various error types that can occur during logger building.

### Request Example
```rust
use flexi_logger::Logger;

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let (logger, _handle) = Logger::try_with_str("info")?.build_with_specfile("logspecification.toml")?;
    // Use the logger manually or nest it
    Ok(())
}
```
```

--------------------------------

### Example: Tail Log File via Symlink

Source: https://docs.rs/flexi_logger/latest/flexi_logger/struct.Logger.html

Demonstrates how to use `tail` with a symbolic link to monitor log files, even after rotation.

```bash
tail --follow=name --max-unchanged-stats=1 --retry link_to_log_file
```

--------------------------------

### Initialize flexi_logger with default settings

Source: https://docs.rs/flexi_logger/latest/flexi_logger/fn.init.html

Use this function for the shortest way to get started with logging. It configures the log specification via the RUST_LOG environment variable or defaults to 'info', and logs directly to stderr.

```rust
flexi_logger::init();
```

```rust
Logger::try_with_env_or_str("info")
       .unwrap_or_else(|_e| Logger::with(LogSpecification::info()))
       .log_to_stderr()
       .start()
       .ok();
```

--------------------------------

### Basic Logger Initialization

Source: https://docs.rs/flexi_logger/latest/flexi_logger/struct.LoggerHandle.html

Demonstrates starting the logger with a simple log level. The LoggerHandle can be ignored if no file or special writer is used.

```rust
use flexi_logger::Logger;
use std::error::Error;
fn main() -> Result<(), Box<dyn Error>> {
    Logger::try_with_str("info")?.start()?;
    // do work
    Ok(())
}
```

--------------------------------

### LoggerHandle Examples

Source: https://docs.rs/flexi_logger/latest/flexi_logger/struct.LoggerHandle.html

Illustrates how to use the LoggerHandle in different scenarios, including basic usage, file logging, and temporary log specification changes.

```APIDOC
## LoggerHandle Examples

### Basic Usage (Ignoring Handle)

In more trivial configurations, dropping the `LoggerHandle` has no effect and then you can safely ignore the return value of `Logger::start()`:

```rust
use flexi_logger::Logger;
use std::error::Error;

fn main() -> Result<(), Box<dyn Error>> {
    Logger::try_with_str("info")?.start()?;
    // do work
    Ok(())
}
```

### File Logging (Keeping Handle Alive)

When logging to a file or another writer, and/or if you use a buffering or asynchronous `WriteMode`, keep the `LoggerHandle` alive until the program ends:

```rust
use flexi_logger::{FileSpec, Logger};
use std::error::Error;

fn main() -> Result<(), Box<dyn Error>> {
    let _logger = Logger::try_with_str("info")? 
        .log_to_file(FileSpec::default())
        .start()?;
    // do work
    Ok(())
}
```

### Permanent Log Specification Change

You can use the logger handle to permanently exchange the log specification programmatically, anywhere in your code:

```rust
    let logger = Logger::try_with_str("info")?.start()?;
    // ...
    logger.parse_new_spec("warn");
    // ...
```

### Temporary Log Specification Change

However, when debugging, you might want to modify the log spec only temporarily, for one or few method calls only; this is easier done with the following method, because it allows switching back to the previous spec:

```rust
    let mut logger = Logger::try_with_str("info")?.start()?;
    logger.parse_and_push_temp_spec("trace");
    // ...
    // critical calls
    // ...
    logger.pop_temp_spec();
    // Continue with the log spec you had before.
    // ...
```
```

--------------------------------

### Logger Initialization with File Logging

Source: https://docs.rs/flexi_logger/latest/flexi_logger/struct.LoggerHandle.html

Shows how to start the logger and direct output to a file. The LoggerHandle must be kept alive to ensure proper file handling and logger shutdown.

```rust
use flexi_logger::{FileSpec, Logger};
use std::error::Error;
fn main() -> Result<(), Box<dyn Error>> {
    let _logger = Logger::try_with_str("info")? 
        .log_to_file(FileSpec::default())
        .start()?;
    // do work
    Ok(())
}
```

--------------------------------

### Example Usage of LogfileSelector

Source: https://docs.rs/flexi_logger/latest/flexi_logger/struct.LogfileSelector.html

Demonstrates how to use LogfileSelector with LoggerHandle::existing_log_files to select specific log files, including the current and compressed files.

```rust
let all_log_files = logger_handle.existing_log_files(
    &LogfileSelector::default()
        .with_r_current()
        .with_compressed_files()
);
```

--------------------------------

### Start Logging with a Specification File

Source: https://docs.rs/flexi_logger/latest/flexi_logger/code_examples/index.html

Initializes the logger using a configuration defined in an external TOML file. This allows for dynamic reconfiguration by editing the file while the program runs.

```rust
Logger::try_with_str("info").unwrap()
    // ... logger configuration ...
   .start_with_specfile("./server/config/logspec.toml")
   .unwrap();
```

--------------------------------

### FileSpec Default Configuration Example

Source: https://docs.rs/flexi_logger/latest/flexi_logger/struct.FileSpec.html

Demonstrates creating a FileSpec with a custom directory, basename, suppressed timestamp, and suffix, then comparing it to a FileSpec derived from a path string. Ensure the path does not exist as a directory.

```rust
assert_eq!(
    FileSpec::default()
        .directory("/a/b/c")
        .basename("foo")
        .suppress_timestamp()
        .suffix("bar"),
    FileSpec::try_from("/a/b/c/foo.bar").unwrap()
);
```

--------------------------------

### Module trc - Setup Tracing Integration

Source: https://docs.rs/flexi_logger/latest/flexi_logger/trc/index.html

This section details how to use flexi_logger functionality with the 'tracing' library. It includes functions for setting up tracing and subscribing to specification file changes.

```APIDOC
## Module trc

### Description
Use `flexi_logger` functionality with `tracing`.

`tracing` is an alternative to `log`. It has a similar base architecture, but is optimized for supporting async apps, which adds complexity due to the need to manage contexts. `tracing-subscriber` facilitates contributing “backends”, and is used by `setup_tracing` to plug `flexi_logger`-functionality into `tracing`.

### Structs

#### FormatConfig
Configuration for the `tracing` formatting.

#### SpecFileNotifier
Rereads the specfile if it was updated and forwards the update to `tracing`’s filter.

### Traits

#### LogSpecSubscriber
Trait that allows to register for changes to the log specification.

### Functions

#### setup_tracing
Set up tracing to write into the specified `FileLogWriter`, and to use the (optionally) specified specfile.

#### subscribe_to_specfile
Allows registering a `LogSpecSubscriber` to a specfile.

### Request Example
```json
{
  "specfile": "/path/to/specfile.toml"
}
```

### Response Example
```json
{
  "status": "success",
  "message": "Tracing setup complete."
}
```
```

--------------------------------

### Configure Default Log File Behavior

Source: https://docs.rs/flexi_logger/latest/flexi_logger/code_examples/index.html

Sets default formatting for stderr, stdout, and files. This example shows the equivalent of FlexiLogger's default initialization.

```rust
// ...
      .adaptive_format_for_stderr(AdaptiveFormat::Default)
      .adaptive_format_for_stdout(AdaptiveFormat::Default)
      .format_for_files(default_format)
      .format_for_writer(default_format)
```

--------------------------------

### Initialize Logger from Environment Variable

Source: https://docs.rs/flexi_logger/latest/flexi_logger/index.html

Use this to initialize the logger with settings read from an environment variable and direct output to stderr. Ensure the `Logger` and `start` methods are available.

```rust
flexi_logger::Logger::try_with_env().unwrap().start().unwrap();
```

--------------------------------

### Timestamps Custom Format Example

Source: https://docs.rs/flexi_logger/latest/flexi_logger/enum.Naming.html

Illustrates the TimestampsCustomFormat variant with a specific current infix and timestamp format. This is equivalent to the Timestamps variant.

```rust
Naming::TimestampsCustomFormat {
   current_infix: Some("rCURRENT"),
    format: "r%Y-%m-%d_%H-%M-%S",
}
```

--------------------------------

### Start Flexi Logger with File Logging

Source: https://docs.rs/flexi_logger/latest/flexi_logger/struct.Logger.html

Initializes flexi_logger with a specified log level and directs output to a file. Ensure the LoggerHandle is kept alive until program termination to prevent premature shutdown of writers.

```rust
use flexi_logger::{Logger,WriteMode, FileSpec};
fn main() -> Result<(), Box<dyn std::error::Error>> {
    let _logger = Logger::try_with_str("info")?
        .log_to_file(FileSpec::default())
        .write_mode(WriteMode::BufferAndFlush)
        .start()?;

    // ... do all your work and join back all threads whose logs you want to see ...

    Ok(())
}
```

--------------------------------

### Setup Tracing with FileLogWriter and Specfile

Source: https://docs.rs/flexi_logger/latest/flexi_logger/trc/fn.setup_tracing.html

Use FileLogWriter as a trace writer with support for dynamically adapting trace levels. The FileLogWriter's formatting is bypassed in favor of tracing's formatting, configurable via FormatConfig. Ensure the returned handles are kept alive until program shutdown.

```rust
use std::{error::Error, path::PathBuf};
use flexi_logger::{
    trc::FormatConfig,
    writers::FileLogWriter,
    Age, Cleanup, Criterion, FileSpec, LogSpecification, Naming, WriteMode,
};


// Drop the keep-alive-handles only in the shutdown of your program
let _keep_alive_handles = flexi_logger::trc::setup_tracing(
    LogSpecification::info(),
    Some(&PathBuf::from("trcspecfile.toml")),
    FileLogWriter::builder(FileSpec::default())
        .rotate(
            Criterion::Age(Age::Day),
            Naming::Timestamps,
            Cleanup::KeepLogFiles(7),
        )
        .write_mode(WriteMode::Async),
        &FormatConfig::default()
           .with_file(true),
)?;

tracing::debug!("now we start doing what we really wanted to do...");

```

--------------------------------

### Define a Simple Logger with flexi_logger

Source: https://docs.rs/flexi_logger/latest/flexi_logger/struct.Record.html

Implement the `log::Log` trait to create a custom logger. This example shows how to process and display log records.

```rust
struct SimpleLogger;

impl log::Log for SimpleLogger {
   fn enabled(&self, _metadata: &log::Metadata) -> bool {
       true
   }

   fn log(&self, record: &log::Record) {
       if !self.enabled(record.metadata()) {
           return;
       }

       println!("{}:{} -- {}",
                record.level(),
                record.target(),
                record.args());
   }
   fn flush(&self) {}
}
```

--------------------------------

### Configure Log File Location and Naming

Source: https://docs.rs/flexi_logger/latest/flexi_logger/code_examples/index.html

Specify a directory, basename, discriminant, and suffix for log files. This example also enables printing a message to stdout indicating the log file location and creates a symbolic link on Unix-like systems.

```rust
Logger::try_with_str("info")? 
    .log_to_file(
        FileSpec::default()
            .directory("log_files")          // create files in folder ./log_files
            .basename("foo")
            .discriminant("Sample4711A")     // use infix in log file name
            .suffix("trc")                   // use suffix .trc instead of .log
    )
    .print_message()                         // 
    .create_symlink("current_run")           // create a symbolic link to the current log file
    .start()?;
```

--------------------------------

### Initialize Logger with Spec File

Source: https://docs.rs/flexi_logger/latest/flexi_logger/struct.Logger.html

Starts flexi_logger using a configuration file for log specifications. The logger will create the spec file if it doesn't exist. The LoggerHandle must be kept alive for the spec file to be dynamically updated.

```rust
use flexi_logger::Logger;
Logger::try_with_str("info")
    .unwrap()
    // more logger configuration
    .start_with_specfile("logspecification.toml");
```

--------------------------------

### Example Log Specification File

Source: https://docs.rs/flexi_logger/latest/flexi_logger/struct.Logger.html

This TOML file defines logging levels and patterns for flexi_logger. It supports a global level, an optional global pattern, and specific levels for different modules.

```toml
### Optional: Default log level
global_level = 'info'
### Optional: specify a regular expression to suppress all messages that don't match
#global_pattern = 'foo'

### Specific log levels per module are optionally defined in this section
[modules]
#'mod1' = 'warn'
#'mod2' = 'debug'
#'mod2::mod3' = 'trace'
```

--------------------------------

### Get Configured Suffix

Source: https://docs.rs/flexi_logger/latest/flexi_logger/writers/struct.FileLogWriterConfig.html

Retrieves the configured suffix for the log file name. Returns an Option<String>.

```rust
pub fn suffix(&self) -> Option<String>
```

--------------------------------

### Example Log File Naming with Rotation

Source: https://docs.rs/flexi_logger/latest/flexi_logger/writers/struct.FileLogWriterBuilder.html

Illustrates the file naming convention when rotation is enabled with `Naming::Numbers`. Log files will have an infix like `_rCURRENT` and be renamed sequentially upon rotation.

```text
my_prog_r00000.log
my_prog_r00001.log
my_prog_r00002.log
my_prog_rCURRENT.log
```

--------------------------------

### Configure and Use Custom Log Writers in Rust

Source: https://docs.rs/flexi_logger/latest/flexi_logger/writers/index.html

This example demonstrates how to configure a `FileLogWriter` for alert messages and use it alongside the default logger. It also shows how to define a macro to simplify sending logs to multiple targets, including the custom 'Alert' target and the default output.

```rust
use log::*; 

use flexi_logger::{FileSpec,Logger};
use flexi_logger::writers::FileLogWriter;

// Configure a FileLogWriter for alert messages
pub fn alert_logger() -> Box<FileLogWriter> {
    Box::new(FileLogWriter::builder(
        FileSpec::default()
            .discriminant("Alert")
            .suffix("alerts")
        )
        .print_message()
        .try_build()
        .unwrap())
}

// Define a macro for writing messages to the alert log and to the normal log
#[macro_use] 
mod macros {
    #[macro_export]
    macro_rules! alert_error {
        ($($arg:tt)*) => ( 
            error!(target: "{Alert,_Default}", $($arg)*);
        )
    }
}

fn main() {
    Logger::try_with_env_or_str("info")
        .expect("LogSpecification String has errors")
        .print_message()
        .log_to_file(FileSpec::default())
        .add_writer("Alert", alert_logger())
        .start()
        .unwrap_or_else(|e| panic!("Logger initialization failed with {}", e));


    // Explicitly send logs to different loggers
    error!(target : "{Alert}", "This is only an alert");
    error!(target : "{Alert,_Default}", "This is an alert and log message");

    // Nicer: use the explicit macro
    alert_error!("This is another alert and log message");

    // Standard log macros write only to the normal log
    error!("This is a normal error message");
    warn!("This is a warning");
    info!("This is an info message");
    debug!("This is a debug message - you will not see it");
    trace!("This is a trace message - you will not see it");
}

```

--------------------------------

### flexi_logger Format Error Example

Source: https://docs.rs/flexi_logger/latest/flexi_logger/error_info/index.html

Indicates an error produced by the chosen log format function. If this occurs with provided format functions, consider opening an issue.

```rust
[flexi_logger][ERRCODE::Format] formatting failed, caused by ...
```

--------------------------------

### TimestampsDirect Custom Format Example

Source: https://docs.rs/flexi_logger/latest/flexi_logger/enum.Naming.html

Illustrates the TimestampsCustomFormat variant with no specific current infix and a timestamp format. This is equivalent to the TimestampsDirect variant.

```rust
Naming::TimestampsCustomFormat {
   current_infix: None,
    format: "r%Y-%m-%d_%H-%M-%S",
}
```

--------------------------------

### Log to File and Duplicate to Stderr

Source: https://docs.rs/flexi_logger/latest/flexi_logger/code_examples/index.html

Configure the logger to write logs to a file and also duplicate warnings and errors to stderr. This example uses a default file specification and the Duplicate::Warn setting.

```rust
Logger::try_with_str("info")?
    .log_to_file(FileSpec::default())         // write logs to file
    .duplicate_to_stderr(Duplicate::Warn)     // print warnings and errors also to the console
    .start()?;

```

--------------------------------

### Implement Stateful Log Filtering with LogLineFilter

Source: https://docs.rs/flexi_logger/latest/flexi_logger/filter/index.html

Demonstrates how to create a custom log filter that only allows log lines containing the word 'bar'. This example requires the `flexi_logger` and `log` crates. The filter is applied using `Logger::filter` after initialization.

```rust
use flexi_logger::{
    filter::{LogLineFilter, LogLineWriter},
    DeferredNow, FlexiLoggerError,
};

pub struct BarsOnly;
impl LogLineFilter for BarsOnly {
    fn write(
        &self,
        now: &mut DeferredNow,
        record: &log::Record,
        log_line_writer: &dyn LogLineWriter,
    ) -> std::io::Result<()> {
        if record.args().to_string().contains("bar") {
            log_line_writer.write(now, record)?;
        }
        Ok(())
    }
}

fn main() -> Result<(), FlexiLoggerError> {
    flexi_logger::Logger::try_with_str("info")? 
        .filter(Box::new(BarsOnly))
        .start()?;
    log::info!("barista");
    log::info!("foo"); // will be swallowed by the filter
    log::info!("bar");
    log::info!("gaga"); // will be swallowed by the filter
    Ok(())
}
```

--------------------------------

### Check if Message is Printed on Program Start

Source: https://docs.rs/flexi_logger/latest/flexi_logger/writers/struct.FileLogWriterConfig.html

Checks if a message indicating the log file path should be printed when the program starts. Returns true if the message is to be printed.

```rust
pub fn print_message(&self) -> bool
```

--------------------------------

### setup_tracing Function

Source: https://docs.rs/flexi_logger/latest/flexi_logger/trc/fn.setup_tracing.html

Sets up tracing to write into a specified `FileLogWriter` and optionally use a specfile for dynamic log level adaptation. Note that the `FileLogWriter`'s formatting is bypassed in favor of `tracing`'s formatting, configurable via `FormatConfig`.

```APIDOC
## setup_tracing

### Description
Sets up tracing to write into the specified `FileLogWriter`, and to use the (optionally) specified specfile. The `FileLogWriter`’s formatting are bypassed and not be used, instead the `tracing` formatting will be used, which can be configured via `config: FormatConfig`.

### Method
`pub fn setup_tracing`

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Parameters
- **initial_logspec** (LogSpecification) - Required - The initial log specification.
- **o_specfile** (Option<&PathBuf>) - Optional - An optional path to a specification file.
- **flwb** (FileLogWriterBuilder) - Required - The builder for the file log writer.
- **config** (&FormatConfig) - Required - The format configuration for tracing.

### Returns
- Result<(FileLogWriterHandle, SpecFileNotifier), FlexiLoggerError> - A tuple containing the file log writer handle and the spec file notifier, or a `FlexiLoggerError`.

### Example
```rust
use std::{error::Error, path::PathBuf};
use flexi_logger::{
    trc::FormatConfig,
    writers::FileLogWriter,
    Age, Cleanup, Criterion, FileSpec, LogSpecification, Naming, WriteMode,
};

// Drop the keep-alive-handles only in the shutdown of your program
let _keep_alive_handles = flexi_logger::trc::setup_tracing(
    LogSpecification::info(),
    Some(&PathBuf::from("trcspecfile.toml")),
    FileLogWriter::builder(FileSpec::default())
        .rotate(
            Criterion::Age(Age::Day),
            Naming::Timestamps,
            Cleanup::KeepLogFiles(7),
        )
        .write_mode(WriteMode::Async),
        &FormatConfig::default()
           .with_file(true),
)?;

tracing::debug!("now we start doing what we really wanted to do...");
```

### Errors
Various variants of `FlexiLoggerError` can occur.
```

--------------------------------

### Get Type ID

Source: https://docs.rs/flexi_logger/latest/flexi_logger/writers/struct.FileLogWriterBuilder.html

Retrieves the `TypeId` of the current object. This is part of the `Any` trait implementation.

```rust
type_id(&self) -> TypeId
```

--------------------------------

### Initialize File Logging with Base Configuration

Source: https://docs.rs/flexi_logger/latest/flexi_logger/code_examples/index.html

Sets up logging to files with a specified base name and directory. The `log` crate and `flexi_logger` must be imported.

```rust
use flexi_logger::{writers::FileLogWriter, Cleanup, Criterion, FileSpec, Naming};

let logger = flexi_logger::Logger::try_with_str("info")?
    .log_to_file(
        FileSpec::default()
            .basename("phase1")
            .directory("./log_files")
    )
    .start()?;

log::info!("start of phase 1");
```

--------------------------------

### Build and Apply Log Specification

Source: https://docs.rs/flexi_logger/latest/flexi_logger/struct.LogSpecBuilder.html

Demonstrates how to build an initial log specification, initialize the logger, and then modify and reapply the specification using LogSpecBuilder.

```rust
use flexi_logger::{Logger, LogSpecification};
use log::LevelFilter;

fn main() {
    // Build the initial log specification
    let mut builder = LogSpecification::builder();
    builder
        .default(LevelFilter::Info)
        .module("karl", LevelFilter::Debug);

    // Initialize Logger, keep builder alive
    let mut logger = Logger::with(builder.build())
        // your logger configuration goes here, as usual
        .start()
        .unwrap_or_else(|e| panic!("Logger initialization failed with {}", e));

    // ...

    // Modify builder and update the logger
    builder
        .default(LevelFilter::Error)
        .remove("karl")
        .module("emma", LevelFilter::Trace);

    logger.set_new_spec(builder.build());

    // ...
}
```

--------------------------------

### Programmatically Change Log Specification

Source: https://docs.rs/flexi_logger/latest/flexi_logger/struct.LoggerHandle.html

Illustrates how to permanently update the logger's specification string after it has been started.

```rust
    let logger = Logger::try_with_str("info")?.start()?;
    // ...
    logger.parse_new_spec("warn");
    // ...
```

--------------------------------

### LogWriter max_log_level Method

Source: https://docs.rs/flexi_logger/latest/flexi_logger/writers/trait.LogWriter.html

Provided method to get the maximum log level to be written. Defaults to `LevelFilter`.

```rust
fn max_log_level(&self) -> LevelFilter { ... }
```

--------------------------------

### Get Configured Directory

Source: https://docs.rs/flexi_logger/latest/flexi_logger/writers/struct.FileLogWriterConfig.html

Retrieves the configured directory path for the FileLogWriter. This method returns a reference to the Path object.

```rust
pub fn directory(&self) -> &Path
```

--------------------------------

### Get Configured Discriminant

Source: https://docs.rs/flexi_logger/latest/flexi_logger/writers/struct.FileLogWriterConfig.html

Retrieves the configured discriminant, which can be used for unique log file identification. Returns an Option<String>.

```rust
pub fn discriminant(&self) -> Option<String>
```

--------------------------------

### LogSpecBuilder - Initialization

Source: https://docs.rs/flexi_logger/latest/flexi_logger/struct.LogSpecBuilder.html

Demonstrates how to create a new LogSpecBuilder and configure initial logging levels.

```APIDOC
## LogSpecBuilder - Initialization

### Description
Initializes a `LogSpecBuilder` and sets default and module-specific log level filters.

### Methods
- `LogSpecification::builder()`: Creates a new `LogSpecBuilder`.
- `default(LevelFilter)`: Sets the default log level filter.
- `module(module_name, LevelFilter)`: Sets the log level filter for a specific module.

### Request Example
```rust
use flexi_logger::{LogSpecification, Logger};
use log::LevelFilter;

let mut builder = LogSpecification::builder();
builder
    .default(LevelFilter::Info)
    .module("karl", LevelFilter::Debug);

let logger = Logger::with(builder.build()).start().unwrap();
```
```

--------------------------------

### Get Configured Basename

Source: https://docs.rs/flexi_logger/latest/flexi_logger/writers/struct.FileLogWriterConfig.html

Retrieves the configured basename for the log file. This is the base name used for log file naming.

```rust
pub fn basename(&self) -> &str
```

--------------------------------

### Get Current Log Specification

Source: https://docs.rs/flexi_logger/latest/flexi_logger/struct.LoggerHandle.html

Obtains a copy of the current log specification. This operation can fail if the internal mutex is poisoned.

```rust
    let spec = logger.current_log_spec()?;
```

--------------------------------

### Check if Appending to Existing Files

Source: https://docs.rs/flexi_logger/latest/flexi_logger/writers/struct.FileLogWriterConfig.html

Determines if existing log files should be appended to when the program starts. Returns true if appending is enabled.

```rust
pub fn append(&self) -> bool
```

--------------------------------

### Get FileLogWriter Configuration

Source: https://docs.rs/flexi_logger/latest/flexi_logger/writers/struct.FileLogWriter.html

Retrieves the current configuration of the FileLogWriter. This can be useful for inspection or for providing configuration details to other methods like `reset`.

```rust
pub fn config(&self) -> Result<FileLogWriterConfig, FlexiLoggerError>
```

--------------------------------

### Get Style for Log Level

Source: https://docs.rs/flexi_logger/latest/flexi_logger/fn.style.html

Helper function to apply colors based on log level. Requires the 'colors' crate feature.

```rust
pub fn style(level: Level) -> Style
```

--------------------------------

### Logger Initialization and Configuration

Source: https://docs.rs/flexi_logger/latest/flexi_logger/struct.Logger.html

Methods for creating and configuring the Logger instance, including setting log level specifications and output destinations.

```APIDOC
## Logger Configuration

### `Logger::with(logspec)`

Creates a Logger with an explicit `LogSpecification`.

#### Parameters
- `logspec` (impl Into<LogSpecification>) - The log specification to use.

#### Examples
```rust
use log::LevelFilter;
use flexi_logger::Logger;
let logger = Logger::with(LevelFilter::Info).start().unwrap();
```

```rust
use flexi_logger::{Logger, LogSpecification};
let logger = Logger::with(
        LogSpecification::parse("info, critical_mod = trace").unwrap()
    ).start().unwrap();
```

### `Logger::try_with_str(s)`

Creates a Logger that reads the `LogSpecification` from a String or &str.

#### Parameters
- `s` (S: AsRef<str>) - The string containing the log specification.

#### Errors
- `FlexiLoggerError::Parse` if the String uses an erroneous syntax.

### `Logger::try_with_env()`

Creates a Logger that reads the `LogSpecification` from the environment variable `RUST_LOG`.

#### Errors
- `FlexiLoggerError::Parse` if the value of `RUST_LOG` is malformed.

### `Logger::try_with_env_or_str(s)`

Creates a Logger that reads the `LogSpecification` from the environment variable `RUST_LOG`, or derives it from the given String, if `RUST_LOG` is not set.

#### Parameters
- `s` (S: AsRef<str>) - The string to use if `RUST_LOG` is not set.

#### Errors
- `FlexiLoggerError::Parse` if the chosen value is malformed.

### Output Destinations

#### `log_to_stderr(self)`

Log is written to stderr (which is the default).

#### `log_to_stdout(self)`

Log is written to stdout.

#### `log_to_file(self, file_spec)`

Log is written to a file. See `FileSpec` for details about the filename pattern.

#### `log_to_writer(self, w)`

Log is written to the provided writer.

#### `log_to_file_and_writer(self, file_spec, w)`

Log is written to a file and an alternative `LogWriter` implementation.

#### `log_to_buffer(self, max_size, format_function)`

Available on **crate feature `buffer_writer`** only. Log is written to an in-memory buffer.

#### `do_not_log(self)`

Log is processed but not written to any destination.

#### `print_message(self)`

Makes the logger print an info message to stdout with the name of the logfile when a logfile is opened for writing.
```

--------------------------------

### Register Custom Log Writer

Source: https://docs.rs/flexi_logger/latest/flexi_logger/struct.Logger.html

Registers a custom `LogWriter` implementation under a specified target name. Target names must not start with an underscore.

```rust
pub fn add_writer<S: Into<String>>( self, target_name: S, writer: Box<dyn LogWriter>, ) -> Self
```

--------------------------------

### Get Maximum Log Level

Source: https://docs.rs/flexi_logger/latest/flexi_logger/writers/struct.FileLogWriter.html

Implements the `max_log_level` method for the LogWriter trait, returning the maximum log level that the writer is configured to handle.

```rust
fn max_log_level(&self) -> LevelFilter
```

--------------------------------

### flexi_logger Write Error Example

Source: https://docs.rs/flexi_logger/latest/flexi_logger/error_info/index.html

Indicates a failure during the writing of a log line to the output. This can occur with asynchronous writers if the logger handle is dropped prematurely.

```rust
[flexi_logger][ERRCODE::Write] writing log line failed, caused by Send
```

--------------------------------

### Configure Log Rotation with Age, Timestamps, and Cleanup

Source: https://docs.rs/flexi_logger/latest/flexi_logger/code_examples/index.html

Sets up file logging with daily rotation, timestamped filenames for rotated files, and keeps a maximum of 7 log files. Ensure the 'log' crate is a dependency.

```rust
Logger::try_with_str("info")?      // Write all error, warn, and info messages
    .log_to_file(
        FileSpec::default()
    )
    .rotate(
        Criterion::Age(Age::Day),
        Naming::Timestamps,
        Cleanup::KeepLogFiles(7),
    )
    .start()?;
```

--------------------------------

### Initialize Flexi Logger with Environment or Programmatic String

Source: https://docs.rs/flexi_logger/latest/flexi_logger/code_examples/index.html

Initialize the logger using both environment variable and a programmatic string, with the environment variable taking precedence. Ensure the log crate is used for logging macros.

```rust
Logger::try_with_env_or_str("info")?.start()?;

```

--------------------------------

### Get FileLogWriter Format Function

Source: https://docs.rs/flexi_logger/latest/flexi_logger/writers/struct.FileLogWriter.html

Retrieves the currently configured output format function for the FileLogWriter. This function determines how log records are formatted before writing.

```rust
pub fn format(&self) -> FormatFunction
```

--------------------------------

### Get Current Maximum Log Level

Source: https://docs.rs/flexi_logger/latest/flexi_logger/struct.LoggerHandle.html

Retrieves the current maximum log level filter applied by the logger. This can fail if the internal mutex is poisoned.

```rust
    let level = logger.current_max_level()?;
```

--------------------------------

### Initialize Flexi Logger Programmatically

Source: https://docs.rs/flexi_logger/latest/flexi_logger/code_examples/index.html

Initialize the logger by providing the log specification string directly. Ensure the log crate is used for logging macros.

```rust
Logger::try_with_str("info")?.start()?;

```

--------------------------------

### Initialize Flexi Logger with Default Settings

Source: https://docs.rs/flexi_logger/latest/flexi_logger/code_examples/index.html

A shorthand for initializing the logger with default settings, typically writing to stderr. Ensure the log crate is used for logging macros.

```rust
flexi_logger::init();

```

--------------------------------

### flexi_logger Flush Error Example

Source: https://docs.rs/flexi_logger/latest/flexi_logger/error_info/index.html

Indicates a failure during explicit or automatic flushing of buffered log lines. Similar reasons to Write errors may apply.

```rust
[flexi_logger][ERRCODE::Flush] flushing primary writer failed, caused by Send
```

--------------------------------

### CloneToUninit for T

Source: https://docs.rs/flexi_logger/latest/flexi_logger/enum.Level.html

Nightly-only experimental API for cloning to uninitialized memory.

```APIDOC
## CloneToUninit for T

### Description
Nightly-only experimental API for cloning to uninitialized memory.

### Method
`clone_to_uninit`

### Endpoint
N/A (Trait implementation)

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Request Example
None

### Response
#### Success Response (200)
None

#### Response Example
None
```

--------------------------------

### Get File Log Writer Configuration

Source: https://docs.rs/flexi_logger/latest/flexi_logger/struct.LoggerHandle.html

Retrieves the current configuration of the file log writer. This operation can fail if no file logger is configured or if a mutex is poisoned.

```rust
    let config = logger.flw_config()?;
```

--------------------------------

### Initialize Flexi Logger with Environment Variable

Source: https://docs.rs/flexi_logger/latest/flexi_logger/code_examples/index.html

Initialize the logger using the RUST_LOG environment variable. Ensure the log crate is used for logging macros.

```rust
Logger::try_with_env()?.start()?;

```

--------------------------------

### From Trait

Source: https://docs.rs/flexi_logger/latest/flexi_logger/writers/struct.ArcFileLogWriter.html

Method for creating an instance from another type.

```APIDOC
## fn from(t: T) -> T

### Description
Returns the argument unchanged. This is part of the `From<T> for T` implementation.

### Method
POST

### Endpoint
N/A (Method within a trait)

### Parameters
- **t** (T) - Required - The value to convert from.

### Request Example
None

### Response
#### Success Response (200)
- **T** (T) - The converted value.

#### Response Example
None
```

--------------------------------

### flexi_logger LogSpecFile Watching Error Example

Source: https://docs.rs/flexi_logger/latest/flexi_logger/error_info/index.html

Indicates a failure while watching the log specification file. This error occurs when the file's monitoring process encounters an issue.

```rust
[flexi_logger][ERRCODE::LogSpecFile] error while watching the specfile, caused by ...
```

--------------------------------

### Include File Name - FormatConfig

Source: https://docs.rs/flexi_logger/latest/flexi_logger/trc/struct.FormatConfig.html

Decides whether to include the file name in the output. Defaults to `false`.

```rust
pub fn with_file(self, with_file: bool) -> Self
```

--------------------------------

### Symlink Creation

Source: https://docs.rs/flexi_logger/latest/flexi_logger/writers/struct.FileLogWriterBuilder.html

Configure the creation of a symbolic link to the current log file on Unix systems.

```APIDOC
## POST /websites/rs_flexi_logger_flexi_logger/o_create_symlink

### Description
On Unix systems, this option creates a symbolic link in the current directory with the specified name, pointing to the current log file.

### Method
POST

### Endpoint
/websites/rs_flexi_logger_flexi_logger/o_create_symlink

### Parameters
#### Request Body
- **symlink** (Option<String>) - Optional - The name of the symbolic link to create.

### Request Example
```json
{
  "symlink": "current_log.log"
}
```

### Response
#### Success Response (200)
- **Self** (Self) - The updated logger configuration.

#### Response Example
```json
{
  "message": "Symlink creation configured successfully"
}
```
```

--------------------------------

### Get Existing Log Files

Source: https://docs.rs/flexi_logger/latest/flexi_logger/writers/struct.FileLogWriterHandle.html

Retrieves a list of existing log files based on the provided LogfileSelector. This can include the current log file and compressed files if they exist.

```rust
pub fn existing_log_files( &self, selector: &LogfileSelector, ) -> Result<Vec<PathBuf>, FlexiLoggerError>
```

--------------------------------

### Create Symbolic Link on Unix

Source: https://docs.rs/flexi_logger/latest/flexi_logger/writers/struct.FileLogWriterBuilder.html

On Unix systems, this creates a symbolic link in the current directory pointing to the current log file.

```rust
pub fn create_symlink<P: Into<PathBuf>>(self, symlink: P) -> Self
```

--------------------------------

### Enable Adaptive Coloring for Stderr

Source: https://docs.rs/flexi_logger/latest/flexi_logger/code_examples/index.html

Conditionally enable colored output for stderr. Colors are used when outputting to a terminal (tty) and suppressed otherwise, for example, when piping to another program.

```rust
flexi_logger::Logger::try_with_str("info")?
    .adaptive_format_for_stderr(AdaptiveFormat::Detailed);
```

--------------------------------

### FormatConfig Configuration

Source: https://docs.rs/flexi_logger/latest/flexi_logger/trc/struct.FormatConfig.html

Configuration options for formatting logs when using flexi_logger with the tracing crate.

```APIDOC
## Struct FormatConfig

### Description
Configuration for the `tracing` formatting. Exposes the formatting capabilities of `tracing-subscriber::FmtSubscriber`. These deviate from the formatting capabilities of `flexi_logger`.

### Methods

#### `with_ansi(self, with_ansi: bool) -> Self`
Decides whether to use ANSI colors in the output. Defaults to `false`.

#### `with_file(self, with_file: bool) -> Self`
Decides whether to include the file name in the output. Defaults to `false`.

#### `with_level(self, with_level: bool) -> Self`
Decides whether to include the log level in the output. Defaults to `true`.

#### `with_line_number(self, with_line_number: bool) -> Self`
Decides whether to include the line number in the output. Defaults to `true`.

#### `with_target(self, with_target: bool) -> Self`
Decides whether to include the target in the output. Defaults to `false`.

#### `with_thread_ids(self, with_thread_ids: bool) -> Self`
Decides whether to include the thread IDs in the output. Defaults to `false`.

#### `with_thread_names(self, with_thread_names: bool) -> Self`
Decides whether to include the thread names in the output. Defaults to `false`.

#### `with_time(self, with_time: bool) -> Self`
Decides whether to include the time in the output. Defaults to `true`.

### Default Implementation

#### `default() -> Self`
Returns the default value for `FormatConfig`.
```

--------------------------------

### Configure Symlink Creation

Source: https://docs.rs/flexi_logger/latest/flexi_logger/struct.Logger.html

On Unix systems, creates a symbolic link in the current folder with the specified name, pointing to the current log file. Has no effect on non-Unix systems or if logs are not written to files.

```rust
pub fn o_create_symlink<P: Into<PathBuf>>(self, symlink: Option<P>) -> Self
```

--------------------------------

### Include Target - FormatConfig

Source: https://docs.rs/flexi_logger/latest/flexi_logger/trc/struct.FormatConfig.html

Decides whether to include the target in the output. Defaults to `false`.

```rust
pub fn with_target(self, with_target: bool) -> Self
```

--------------------------------

### Build FileLogWriter

Source: https://docs.rs/flexi_logger/latest/flexi_logger/writers/struct.FileLogWriterBuilder.html

Constructs and returns a `FileLogWriter` instance. Returns `FlexiLoggerError::Io` if the specified path is invalid.

```rust
pub fn try_build(self) -> Result<FileLogWriter, FlexiLoggerError>
```

--------------------------------

### flexi_logger LogSpecFile Rereading Error Example

Source: https://docs.rs/flexi_logger/latest/flexi_logger/error_info/index.html

Indicates that rereading the log specification file failed, causing the logger to continue with the previous specification. This can happen if the file cannot be opened, read, or parsed.

```rust
[flexi_logger][ERRCODE::LogSpecFile] continuing with previous log specification,
because rereading the log specification file failed, caused by ...
```

--------------------------------

### SyslogConnection Factory Methods

Source: https://docs.rs/flexi_logger/latest/flexi_logger/writers/struct.SyslogConnection.html

Methods for creating SyslogConnection instances, each tailored for different syslog configurations and environments.

```APIDOC
## SyslogConnection

Implements the connection to the syslog. Choose one of the factory methods that matches your environment, depending on how the syslog is managed on your system, how you can access it and with which protocol you can write to it. Is required to instantiate a `SyslogWriter`.

### `try_datagram<P: AsRef<Path>>(path: P) -> IoResult<Self>`

**Available on `Unix` only.**

Returns a `Syslog` that connects via unix datagram to the specified path.

**Errors:**
Any kind of I/O error can occur.

### `try_stream<P: AsRef<Path>>(path: P) -> IoResult<Self>`

**Available on `Unix` only.**

Returns a `Syslog` that connects via unix stream to the specified path.

**Errors:**
Any kind of I/O error can occur.

### `syslog_call() -> Self`

**Available on `Unix` only.**

Returns a `Syslog` that delegates on the POSIX-standard `syslog` C function provided by the platform’s standard C library to send logs. This is ideal for portably sending logs to whatever system logging service may be available.

### `try_tcp<T: ToSocketAddrs>(server: T) -> IoResult<Self>`

Returns a `Syslog` that sends the log lines via TCP to the specified address.

**Errors:**
`std::io::Error` if opening the stream fails.

### `try_udp<T: ToSocketAddrs>(local: T, server: T) -> IoResult<Self>`

Returns a `Syslog` that sends the log via the fragile UDP protocol from local to server.

**Errors:**
`std::io::Error` if opening the stream fails.
```

--------------------------------

### Conditionally Print Info Message

Source: https://docs.rs/flexi_logger/latest/flexi_logger/writers/struct.FileLogWriterBuilder.html

Controls whether an info message is printed to stdout when a new log file is used. This method allows flexible control, for example, based on command-line arguments.

```rust
pub fn o_print_message(self, print_message: bool) -> Self
```

--------------------------------

### Configure Log File Rotation

Source: https://docs.rs/flexi_logger/latest/flexi_logger/writers/struct.FileLogWriterBuilder.html

Set up log file rotation based on size and cleanup strategy. The size is specified in bytes. A cleanup strategy can limit disk space usage.

```rust
o_rotate(self, rotate_config: Option<(Criterion, Naming, Cleanup)>)
```

--------------------------------

### Create Symbolic Link for Log File

Source: https://docs.rs/flexi_logger/latest/flexi_logger/writers/struct.FileLogWriterBuilder.html

On Unix-like systems, create a symbolic link with a specified name in the current folder that points to the current log file. This is useful for easily accessing the latest log.

```rust
o_create_symlink<S: Into<PathBuf>>(self, symlink: Option<S>)
```

--------------------------------

### Create Symbolic Link

Source: https://docs.rs/flexi_logger/latest/flexi_logger/struct.Logger.html

Creates a symbolic link to the current log file on Unix systems.

```APIDOC
## POST /create_symlink

### Description
Creates a symbolic link to the current log file on Unix systems. This is useful for following log output with tools like `tail`.

### Method
POST

### Endpoint
/create_symlink

### Parameters
#### Request Body
- **symlink** (P: Into<PathBuf>) - Required - The path for the symbolic link to be created.
```
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