# View packet logs using logcat

The logs produced by most Caplin Platform components are simple text files that can be viewed using a suitable text display utility or text editor, such as the Linux commands `cat`, `more`, and `vim`. However the packet logs are in binary format and must be viewed using the Caplin `logcat` utility. Here’s how to do this.

## Running logcat

There’s a copy of the `logcat` utility in the `bin` directory of each installed [Liberator](../liberator/index.md), [Transformer](../transformer/index.md) and [Integration Adapter](../platform-architecture/putting-data-into-the-platform.md).

In the [Caplin Deployment Framework](../deployment-framework/index.md), you’ll find `logcat` in the following places:

* `<Framework-root>/servers/Liberator/bin`
* `<Framework-root>/servers/Transformer/bin`
* `<Framework-root>/kits/<Adapter-blade-name>/<Adapter-blade-name>/DataSource/bin`

where `<Framework-root>` is the Deployment Framework’s topmost directory.

**📌 NOTE**\
You can generally use any instance of `logcat` in your Framework to view any of the packet logs produced by any component running under the Framework. However, we recommend that you normally use the latest `logcat` whenever possible; that is, the `logcat` provided in the latest kit version out of all the component kits you’ve deployed in the Framework.

You use `logcat` in a similar way to the standard Linux `cat` command. So, if you’re in the directory where `logcat` resides, you enter a command of the form:

```
./logcat [options] <path-and-name-of-binary-log-file>
```

The logcat utility takes the following options:

| logcat option (short form) | logcat option (long form) | Usage |
| --- | --- | --- |
| `-h` | `--help` | Displays detailed information about the available logcat options. |
| `-F` | `--print-field-names` | Displays the names of the fields in each log record (the default is to just print the field numbers). The field names are obtained from the component’s [fields file](datasource-field-definitions.md) (see `-f` option). |
| `-f <fields-file>` | `--fields-file <fields-file>` | The location (directory path) and name of the fields file. The default setting if you don’t provide a `-f` option is `fields.conf` in the current directory. |
| +[not available]+ | `--print-info` | Displays the version, type and source of the log. For example: `Logcat: Log Type 'packet' Version 5 created by 'rttpd' in timezone 'Europe/London'` The timezone reported is that of the local machine that the logs were written on. |
| `-l` | `--print-flag-names` | Displays the flags that have been sent with each data object; for example `F_NONACTIVE|F_CREATEPARENT|F_CREATEOBJECT` For an explanation of what each flag means, see the Data Object Flags module of the _[DataSource C (DSDK) API Documentation,opts="nofollow"](https://docs.caplin.com/developer/api/datasource_c/6/)._ |
| `-t packet` | `--log-type packet` | Tells `logcat` to interpret the supplied file as a particular type. This option takes an argument. Currently the only argument available is `packet` which makes `logcat` interpret the file as a packet log. Normally `logcat` determines the type of the binary log file by looking at a header record within the file, However, you’ll need to use the `-t` option if you’ve split the file into smaller pieces, because the header will be missing from the smaller file. See [Splitting packet logs into smaller files](#splitting-packet-logs-into-smaller-files), below. Example: `logcat -t packet mypacket.log` |
| `-U <status-file>` | `--update-file <stats-file>` | Specifies the name (and optionally the path) of a file to which `logcat` will write update rate statistics, based on an analysis of the supplied packet log file. |
| +[not available]+ | `--log-version <version-num>` | Specifies the version of the log file, which is then checked against the log versions that this instance of `logcat` can handle. This option only has an effect when you pipe the log file to `logcat` from another tool, such as `tail` For example: `tail -f <packet-log-file> | logcat --log-version 7` Since the log file header, which identifies the log version, isn’t usually available to `logcat` via `tail`, `logcat` takes the supplied `<version-num>` to be the log version instead and formats the file contents accordingly. If `<version-num>` is greater than the maximum log file version that this instance of `logcat` can handle, `logcat` terminates with a version warning message. So in the above example, if `logcat` cannot handle log versions greater than `5`, it displays the following message and then exits: `Logcat: The Log 'Pipe' is of a newer version (7) than I can handle` |
| `-x` | `--print-id` | Displays the [`datasrc-id`](datasource-datasource-peers-configuration-part-2.md#datasrc-id) of the peer referred to in a packet. By default, `logcat` displays the peer’s name as referred to by it’s [`datasrc-local-label`](datasource-datasource-peers-configuration-part-2.md#datasrc-local-label), if that is available. |
| `-z <timezone>` | `--timezone <timezone>` | Sets all times in the log to the specified timezone. To find the required timezone look in the system folder `zoneinfo`, typically found at `/usr/share/lib/zoneinfo` or `/usr/share/zoneinfo` In this folder there are sub folders with timezone information in them; for example, if there’s a subfolder called ``US/Mountain`’, set the timezone option as `-z US/Mountain` |

## Examples

These examples are for a Liberator packet log. The current working directory is the Liberator’s `var` directory, where the packet logs are usually located. The default name of Liberator’s packet log is `packet-rttpd.log` - (see the [`datasrc-pkt-log`](datasource-datasource-peers-configuration-part-2.md#datasrc-pkt-log) configuration item in [DataSource peers configuration (part 2)](datasource-datasource-peers-configuration-part-2.md)).

**Example 1:**

```
../bin/logcat --print-info packet-rttpd.log
```

This outputs:

```
Logcat: Log Type 'packet' Version 5 created by 'rttpd' in timezone 'Europe/London'
```

**Example 2:**

```
../bin/logcat packet-rttpd.log
```

This outputs the following (only the first few lines are shown):

```
2015/09/22-14:10:57.112 +0100: 0.0.0.0 < PEERINFO 102 transformer1 0  ACTIVE|CONTRIB Handshake data: 
datasrc-version=6.2.5-301125, hostname=johne-960, platform=i686-pc-win32, technology=DSDK, transformer-version=6.2.5-301153,
pipeline-module-loaded=true, pipeline-module-version=6.2.5-301153, format-module-loaded=true, 
format-module-version=6.2.5-301153, autopub-module-loaded=true, autopub-module-version=6.2.5-301153, 
cluster-module-loaded=true
2015/09/22-14:10:57.112 +0100: 127.0.0.1 > PEERINFO 101 liberator1 0  BROADCAST Handshake data: 
datasrc-version=6.2.5-301125, hostname=johne-960, platform=i686-pc-win32, technology=DSDK, liberator-version=6.2.6-301198, 
liberator-auth-module=openauth
2015/09/22-14:10:57.113 +0100: 127.0.0.1 > HEARTBEAT transformer1 15 0
2015/09/22-14:10:57.114 +0100: 127.0.0.1 < HEARTBEAT transformer1 15 0
2015/09/22-14:11:00.297 +0100: 0.0.0.0 < PEERINFO DemoDataSource1 DemoDataSource-johne-960 0 DemoDataSource1 ACTIVE|CONTRIB
Handshake data: datasrc-version=6.2.5-301125, hostname=johne-960, platform=i686-pc-win32, technology=DSDK
2015/09/22-14:11:00.297 +0100: 127.0.0.1 > PEERINFO 101 liberator1 0  BROADCAST Handshake data: 
datasrc-version=6.2.5-301125, hostname=johne-960, platform=i686-pc-win32, technology=DSDK, liberator-version=6.2.6-301198, 
liberator-auth-module=openauth
2015/09/22-14:11:00.297 +0100: 127.0.0.1 > HEARTBEAT DemoDataSource1 15 0
2015/09/22-14:11:00.298 +0100: 127.0.0.1 < HEARTBEAT DemoDataSource1 15 0
2015/09/22-14:11:00.392 +0100: 127.0.0.1 < DATAUPDATE2 DemoDataSource1 1 8240 /EXAMPLES/BROADCAST/ABC 222 3 
-11001=Value 0.243902 -11002=Value 0.149254 -11003=Value 0.294118
2015/09/22-14:11:00.396 +0100: 127.0.0.1 < DATAUPDATE2 DemoDataSource1 2 8240 /EXAMPLES/BROADCAST/DEF 222 3 
-11001=Value 1.#INF00 -11002=Value 0.144928 -11003=Value 0.416667
2015/09/22-14:11:00.397 +0100: 127.0.0.1 < DATAUPDATE2 DemoDataSource1 3 8240 /EXAMPLES/BROADCAST/GHI 222 3 
-11001=Value 0.128205 -11002=Value 0.172414 -11003=Value 0.161290
...
```

## Displaying the last part of the log file in real time

You can use the Linux `tail` command with `logcat` to display the last part of the log file and update the screen when more data appears.

Example:

```
tail -f packet-rttpd.log | ../bin/logcat -t packet
```

## Splitting packet logs into smaller files

Packet logs can become very large. To make it easier to view a large packet log, you can split it into smaller files first, using the Linux `split` command.

Example:

```
split -b 10m packet.log
```

This example splits the log into separate files of 10 megabytes each.

**⚠️ WARNING**\
The `split` command can produce a lot of files if you’re not careful with the size parameter.

When you use `logact` to view one of the split files (other than the first one), you must tell it that the file is a packet log, because the file’s header will now be missing:

```
logcat -t packet packet-xab
```

---

**See also:**

* How can I... [Disable packet logging](datasource-disable-packet-logs-for-c-datasource.md)