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A python module for regular expression manipulations.

Project description

rex
====
[![PyPI Version](https://img.shields.io/pypi/v/rexutil.svg)](https://pypi.python.org/pypi/rexutil)

A simple python module which serves as an abstraction to the python
regular expression (re) module in some use cases.

+ [Introduction] (https://github.com/bdastur/rex/blob/master/README.md#introduction)
+ [Getting Started] (https://github.com/bdastur/rex/blob/master/README.md#getting-started)
+ [Features] (https://github.com/bdastur/rex/blob/master/README.md#features)
+ [LR Value Parsing] (https://github.com/bdastur/rex/blob/master/README.md#lrvalue)
+ [Multiple LR Value Parsing] (https://github.com/bdastur/rex/blob/master/README.md#mlrvalue)
+ [Table formatParsing] (https://github.com/bdastur/rex/blob/master/README.md#tabular)
+ [RE Pattern Abstractions] (https://github.com/bdastur/rex/blob/master/README.md#pabstractions)


------
# Introduction:<a name="introduction"></a>

The rex module was born out of necessity. I found myself writing code to parse a lot of command line output for some switches which did not have a good API interface and also in some cases where CLI was the best option to get the data I needed.

In a lot of cases the output format was very similar where I could generalize and try to come up with a common API that can be used for any such CLI. I could not find anything that would fit the bill, and rex was born.

------
# Getting Started:<a name="getting-started"></a>


## Installing using pip:
```
pip install rexutil
```

## Installing (git clone):
```
git clone https://github.com/bdastur/rex -b master
```

## Usage:
```
import rex
```

------
# Features:<a name="features"></a>
The module provides the following main abstractions:

## **1. Parsing a LR Value String:**<a name="lrvalue"></a>
Consider the output of a CLI "show chassis" below from a switch.
```
chassis : UCS43
Serial no : USC788dc
Firmware : 12.01(99)
PID : UCS4343
UUID : URY888dR7R7R8-090-99
Description : Ucs M3 Series Chassis

```
The LRValue parser will parse this output and return a dictionary:
```
{
'firmware': '12.01(99)',
'description': 'Ucs M3 Series Chassis',
'serial_no': 'USC788dc',
'pid': 'UCS4343',
'chassis': 'UCS43',
'uuid': 'URY888dR7R7R8-090-99'
}
```

## **2. Parsing multiple LR Value strings.**<a name="mlrvalue"></a>
A similar use case is where you have multiple blocks of LRValue paris.
Consider the example of a CLI to display adapters.
```
Physical Drive Number 21:
Controller: SLOT-4
Health: Good
Status: Unconfigured Good
Manufacturer: ATA
Model: ST91000640NS
Predictive Failure Count: 0
Drive Firmware: CC03
Coerced Size: 952720 MB
Type: HDD
Physical Drive Number 22:
Controller: SLOT-4
Health: Good
Status: Unconfigured Good
Manufacturer: ATA
Model: ST91000640NS
Predictive Failure Count: 0
Drive Firmware: CC03
Coerced Size: 952720 MB
```

In this case the LRValue parser will parse the output and
return a list of dictionary object
```
[ { },
{ 'coerced_size': '952720 MB',
'controller': 'SLOT-4',
'drive_firmware': 'CC03',
'health': 'Good',
'manufacturer': 'ATA',
'model': 'ST91000640NS',
'physical_drive_number': '',
'predictive_failure_count': '0',
'status': 'Unconfigured Good',
'type': 'HDD'},
{ 'coerced_size': '952720 MB',
'controller': 'SLOT-4',
'drive_firmware': 'CC03',
'health': 'Good',
'manufacturer': 'ATA',
'model': 'ST91000640NS',
'physical_drive_number': '',
'predictive_failure_count': '0',
'status': 'Unconfigured Good'}]
```

## **3. Parsing a tabular format string.**<a name="tabular"></a>
Very common output format is a tabular format with fields seperated by
delimiters (spaces, |, etc).

An example here is the "df" command:
```
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/md1 95926932 27688272 63359156 31% /
udev 132014724 4 132014720 1% /dev
tmpfs 52809712 448 52809264 1% /run
none 5120 0 5120 0% /run/lock
none 132024280 0 132024280 0% /run/shm
cgroup 132024280 0 132024280 0% /sys/fs/cgroup
/dev/md0 943544 28960 865820 4% /boot
/dev/md2 806415824 63998212 701447384 9% /var
```

Here the taubular string parser will parse the output, and return a list
of dictionary objects as below:
```
[ { '1k-blocks': '95926932',
'Available': '63359156',
'Filesystem': '/dev/md1',
'Mounted_on': '/',
'usage%': '31%',
'used': '27688272'},
{ '1k-blocks': '132014724',
'Available': '132014720',
'Filesystem': 'udev',
'Mounted_on': '/dev',
'usage%': '1%',
'used': '4'},
{ '1k-blocks': '52809712',
'Available': '52809264',
'Filesystem': 'tmpfs',
'Mounted_on': '/run',
'usage%': '1%',
'used': '448'},
{ '1k-blocks': '5120',
'Available': '5120',
'Filesystem': 'none',
'Mounted_on': '/run/lock',
'usage%': '0%',
'used': '0'},
{ '1k-blocks': '132024280',
'Available': '132024280',
'Filesystem': 'none',
'Mounted_on': '/run/shm',
'usage%': '0%',
'used': '0'},
{ '1k-blocks': '132024280',
'Available': '132024280',
'Filesystem': 'cgroup',
'Mounted_on': '/sys/fs/cgroup',
'usage%': '0%',
'used': '0'},
{ '1k-blocks': '943544',
'Available': '865820',
'Filesystem': '/dev/md0',
'Mounted_on': '/boot',
'usage%': '4%',
'used': '28960'},
{ '1k-blocks': '806415824',
'Available': '701447384',
'Filesystem': '/dev/md2',
'Mounted_on': '/var',
'usage%': '9%',
'used': '63998212'}]

```


## **4. Common (re) Pattern Abstractions**<a name="pabstractions"></a>
Another use case where parsing strings is needed is in logs and other program output.
Some of the common patterns which can abstract a lot of pain in writing regular expression strings
are below:

### 1. IP Address:
Here is an example of a log from haproxy:
```
Nov 16 16:35:06 testhost1 haproxy[37217]: 192.16.41.8:45133 [16/Nov/2015:16:32:04.152] mysql mysql/mysql1 1/0/182236 12736 -- 647/261/261/261/0 0/0
Nov 16 16:35:06 testhost1 haproxy[37217]: 192.16.41.8:45100 [16/Nov/2015:16:32:03.525] mysql mysql/mysql1 1/0/182932 13077 -- 647/261/261/261/0 0/0
Nov 16 16:35:06 testhost1 haproxy[37217]: 192.16.41.8:45131 [16/Nov/2015:16:32:04.105] mysql mysql/mysql1 1/0/182483 12592 -- 647/261/261/261/0 0/0
Nov 16 16:35:07 testhost1 haproxy[37217]: 192.16.41.8:45182 [16/Nov/2015:16:32:05.396] mysql mysql/mysql1 1/0/182246 8352 -- 647/261/261/261/0 0/0
Nov 16 16:35:07 testhost1 haproxy[37217]: 192.16.41.4:55572 [16/Nov/2015:16:32:07.711] mysql mysql/mysql1 1/0/180119 16915 -- 647/261/261/261/0 0/0

```

Consider we want to parse the log and get all the ip addresses and ports. Here is how we can do that
using the rex reformat pattern API.

First we define our search pattern:
```
# Get the ipaddress and port no from the output.
pattern = ".* (ip:<ipaddr>):(d:<port>).*"
```

Invoke the rex "reformat_pattern() API.
```
rexpat = rex.reformat_pattern(pattern)
```

Now we can use this as a pattern to search. In this case the re.finditer to iterate
through all the matches:
```
for mobj in re.finditer(rexpat, data):
print "IP ADDR: %s, PORT: %s" % \
(mobj.group(1), mobj.group(2))
```

This returns the output:
```
IP ADDR: 192.16.41.8, PORT: 45133
IP ADDR: 192.16.41.8, PORT: 45100
IP ADDR: 192.16.41.8, PORT: 45131
IP ADDR: 192.16.41.8, PORT: 45182
IP ADDR: 192.16.41.4, PORT: 55572
```

### 2. MAC Addresses:

### 3. Timestamps:

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