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# logcat

The Android logging system provides a mechanism for collecting and viewing system debug output. Logs from various applications and portions of the system are collected in a series of circular buffers, which then can be viewed and filtered by the `logcat` command. You can use `logcat` from an ADB shell to view the log messages.

This document is a reference to the available command line options. For more information on `logcat`, see Reading and Writing Logs. For more information on accessing `logcat` from DDMS, instead of the command line, see the documentation for the Dalvik Debug Monitor Server.

### Syntax

    [adb] logcat [<option>] ... [<filter-spec>] ...

You can run `logcat` as an adb command or directly in a shell prompt of your emulator or connected device. To view log output using adb, navigate to your SDK `platform-tools/` directory and execute:

    $ adb logcat

You can create a shell connection to a device and execute:

    $ adb shell
    # logcat

### Options

The following table describes the command line options of `logcat`.

Option | Description
--- | ---
`-b <buffer>` | Loads an alternate log buffer for viewing, such as `event` or `radio`. The `main` buffer is used by default. See Viewing Alternative Log Buffers.
`-c` | Clears (flushes) the entire log and exits.
`-d` | Dumps the log to the screen and exits.
`-f <filename>` | Writes log message output to `<filename>`. The default is `stdout`.
`-g` | Prints the size of the specified log buffer and exits.
`-n <count>` | Sets the maximum number of rotated logs to `<count>`. The default value is 4. Requires the `-r` option.
`-r <kbytes>` | Rotates the log file every `<kbytes>` of output. The default value is 16. Requires the `-f` option.
`-s` | Sets the default filter spec to silent.
`-v <format>` | Sets the output format for log messages. The default is `brief` format. For a list of supported formats, see Controlling Log Output Format.

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