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Sun, Oct 29, 2017 10:10 pm

Decoding base64-encoded text in a .eml file with Python

I received an email message from someone that contained an attachment that had a .eml filename extension. When I viewed that file, I found the usual email header fields, i.e., "from", "to", "cc", and "subject", but for the body of the message I saw the following:

Content-Type: multipart/alternative;
MIME-Version: 1.0

Content-Type: text/plain; charset="utf-8"
Content-Transfer-Encoding: base64

<text snipped>


I needed to decode the base64 encoded text. Fortunately, Python has a base64 module that can be used for that purpose. So I created the following Python script to decode the encoded portion of the .eml file. The script expects the name of the input file to be provided on the command line and will print an error message and terminate if the file name isn't provided. If the filename is provided, the script will read the file line by line looking for the "Content-Transfer-Encoding: base64" which indicates that after one following blank line the encoded text will commence. The output will be displayed on the screen but can be redirected to a file.


import base64, sys

except IndexError:
   print "Error - missing input file name! Usage", sys.argv[0], "infile"
   fileName = sys.argv[1]

base64_marker = "Content-Transfer-Encoding: base64"
block_of_lines = ""

with open(fileName) as input_data:
    # Skips text before the beginning of the base64 encoded block:
    for line in input_data:
        if line.strip() == 'Content-Transfer-Encoding: base64':
    for line in input_data:  # Skip blank line
    # Reads text until the end of the block:
    for line in input_data:  # Append lines to block_of_lines
        block_of_lines = block_of_lines + line
    print base64.b64decode(block_of_lines)

[/languages/python] permanent link

Sat, Oct 28, 2017 10:45 pm

Checking operating system information with WMIC

You can use wmic os get commands on a Microsoft Windows system to view information related to the operating system via a command-line interface (CLI). E.g., to determine the version of the operating system you can issue the command Windows Management Instrumentation Command-line (WMIC) command wmic os get version.

C:\Users\Public>wmic os get version


Or if you know the system is running a particular version of the Windows operating system, e.g., Windows 10, but want to see just the build number for that version of Windows, you could issue the command wmic os get BuildNumber.

C:\Users\Public>wmic os get BuildNumber


[ More Info ]

[/os/windows/commands/wmic] permanent link

Wed, Oct 25, 2017 10:36 pm

Viewing the fonts used in a PDF document on a Mac OS X system

To view the list of documents contained in a PDF document with Adobe Acrobat Reader DC on a Mac OS X system, with the file open in Acrobat Reader DC, click on File then select Properties and then click on the Fonts tab.

Adobe Acrobat Reader DC fonts list

[ More Info ]

[/os/os-x] permanent link

Sun, Oct 22, 2017 11:09 pm

Text not printing, PowerShell cmdlets not working, etc.

A user reported that when she printed Microsoft Excel spreadsheets or QuickBooks invoices, no text would appear on the printouts. She had reported the same problem about a month ago. When I rebooted the system then, the problem went away, but this time rebooting didn't help. After I requested that she reboot the system, I was told the problem remained, so when I was able to get to the system to troubleshoot, I first checked to make sure the system had been rebooted rather than QuickBooks simply being restarted. It was then that I noticed a lot of other functionality was no longer available. E.g., when I tried to use the systeminfo command to find the last reboot time, I saw an error message instead of the time the system was last rebooted.

Microsoft Windows [Version 10.0.15063]
(c) 2017 Microsoft Corporation. All rights reserved.

C:\Users\Pam>systeminfo | find /i "Boot"
Loading Operating System Information ...ERROR: Invalid class

Loading Operating System Information ...ERROR: Invalid class

C:\Users\Pam>wmic os get lastbootuptime
os - Alias not found.


[ More Info ]

[/os/windows/win10] permanent link

Sat, Oct 21, 2017 10:13 pm

Using PowerShell to determine the installed version of Windows

You can determine the version of Microsoft Windows installed on a system from a PowerShell prompt using [System.Environment]::OSVersion.Version or (Get-WmiObject -class Win32_OperatingSystem).Caption.

PS C:\Users\Public> [System.Environment]::OSVersion.Version

Major  Minor  Build  Revision
-----  -----  -----  --------
10     0      15063  0

PS C:\Users\Public> (Get-WmiObject -class Win32_OperatingSystem).Caption
Microsoft Windows 10 Pro
PS C:\Users\Public> (Get-WmiObject -class Win32_OperatingSystem)

SystemDirectory : C:\WINDOWS\system32
Organization    : Microsoft
BuildNumber     : 15063
RegisteredUser  : Jeanne
SerialNumber    : 00330-80000-00000-AA775
Version         : 10.0.15063

PS C:\Users\Public>

[ More Info ]

[/os/windows/PowerShell] permanent link

Fri, Oct 20, 2017 10:57 pm

Querying disks with the PowerShell Get-Disk cmdlet

You can use the PowerShell Get-Disk cmdlet to query disk drives within or attached to a PC running the Microsoft Windows operating system. E.g.:

PS C:\Users\Public> Get-Disk

Number Friendly Name Serial Number                    HealthStatus         OperationalStatus      Total Size Partition
------ ------------- -------------                    ------------         -----------------      ---------- ----------
0      ST3320418AS               9VMNNJDN             Healthy              Online                  298.09 GB MBR
4      Generic- C... 058F63626421                     Healthy              No Media                      0 B RAW
6      Generic- M... 058F63626423                     Healthy              No Media                      0 B RAW
3      Generic- S... 058F63626420                     Healthy              No Media                      0 B RAW
5      Generic- S... 058F63626422                     Healthy              No Media                      0 B RAW
1      Lexar USB ... AA58ZF9FJCCALAOA                 Healthy              Online                   14.92 GB MBR
2      WD My Pass... WXP1A27034VH                     Healthy              Online                  931.48 GB GPT

PS C:\Users\Public>

[ More Info ]

[/os/windows/PowerShell] permanent link

Sat, Oct 14, 2017 8:59 pm

Text_factory that can support 8-bit bytestrings

I wrote a Python script that will download a webpage, extract a portion of the text displayed on the page and write the extracted portion to an SQLite database. When I ran the script, I saw the message below displayed:

You must not use 8-bit bytestrings unless you use a text_factory that can interpret 8-bit bytestrings (like text_factory = str). It is highly recommended that you instead just switch your application to Unicode strings.

I had created the following function to establish the connection to the SQLITE 3 database:

def create_connection (db_file):
   """ Create a database connection to an SQL database
       Return connection object or none """
      conn = sqlite3.connect(db_file)
      return conn
   except Exception as e:
   return None

[ More Info ]

[/languages/python] permanent link

Fri, Oct 13, 2017 10:59 pm

Checking the uptime for a Windows system using PowerShell

If you want to determine how long a Microsoft system has been running since it was last rebooted from a command-line interface (CLI), you can do so using PowerShell. You can do so by subtracting the last boot time from the current date and time. The Get-Date cmdlet shows the current date and time and (Get-CimInstance Win32_OperatingSystem).LastBootUpTime shows the last time the system was booted.

PS C:\Users\public\documents> (Get-CimInstance Win32_OperatingSystem).LastBootUpTime

Tuesday, October 10, 2017 9:12:14 PM

PS C:\Users\public\documents> (Get-Date) - (Get-CimInstance Win32_OperatingSystem).LastBootUpTime

Days              : 3
Hours             : 1
Minutes           : 29
Seconds           : 26
Milliseconds      : 717
Ticks             : 2645667172021
TotalDays         : 3.06211478243171
TotalHours        : 73.4907547783611
TotalMinutes      : 4409.44528670167
TotalSeconds      : 264566.7172021
TotalMilliseconds : 264566717.2021

PS C:\Users\public\documents>

You can use the alias GCIM for Get-CimInstance to save some typing, if you wish.

PS C:\Users\public\documents> (GCIM Win32_OperatingSystem).LastBootUpTime

Tuesday, October 10, 2017 9:12:14 PM

PS C:\Users\public\documents>

[/os/windows/PowerShell] permanent link

Wed, Oct 11, 2017 10:20 pm

Error stating Outlook OST file is in use and cannot be accessed

After I rebooted a Windows 10 PC subsequent to a software update on the system, when I attempted to reopen Microsoft Outlook 2016, I saw the message below:

Outlook Data File

Black exclamation
mark in yellow triangle The file C:\Users\jasmith1\AppData\Local\Microsoft\Outlook\ is in use and cannot be accessed. Close any application that is using this file, and then try again. You might need to restart your computer.

[ More Info ]

[/network/email/clients/outlook/2016] permanent link

Tue, Oct 10, 2017 11:31 pm

Wget and curl functionality via PowerShell on a Windows system

If you are accustomed to using the wget or cURL utilities on Linux or Mac OS X to download webpages from a command-line interface (CLI), there is a Gnu utility, Wget for Windows , that you can download and use on systems running Microsoft Windows. Alternatively, you can use the Invoke-WebRequest cmdlet from a PowerShell prompt, if you have version 3.0 or greater of PowerShell on the system. You can determine the version of PowerShell on a system by opening a PowerShell window and typing $psversiontable. E.g., in the example below from a Windows 10 system, the version of PowerShell is 5.1.15063.674.

PS C:\Users\public\documents> $psversiontable

Name                           Value
----                           -----
PSVersion                      5.1.15063.674
PSEdition                      Desktop
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0...}
BuildVersion                   10.0.15063.674
CLRVersion                     4.0.30319.42000
WSManStackVersion              3.0
PSRemotingProtocolVersion      2.3

PS C:\Users\public\documents>

If you have version 3.0 or later, you can use wget or curl as an alias for the Invoke-WebRequest cmdlet, at least up through version 5.x. E.g., if I want to download the home page for the website to a file named index.html, I could use the command wget -OutFile index.html at a PowerShell prompt. Or I could use either of the following commands, instead:

curl -OutFile index.html
Invoke-WebRequest -OutFile index.html

[ More Info ]

[/os/windows/PowerShell] permanent link

Mon, Oct 09, 2017 11:13 pm

Checking the version of a Dynamic Link Library (DLL) file

You can check version information for a Dynamic-link Library (DLL) file, i.e., a file with a .dll filename extension, or a executable file, i.e., a .exe file, from a command-line interface (CLI) on a Microsoft Windows system by using the Get-Item cmdlet. E.g.:

PS C:\> (Get-Item C:\Windows\explorer.exe).VersionInfo

ProductVersion   FileVersion      FileName
--------------   -----------      --------
10.0.15063.0     10.0.15063.0 ... C:\Windows\explorer.exe

PS C:\>

If you can't see all of the information, i.e., if you see three dots indicating that not all of the information is displayed, you can append | format-list to the command to have the output displayed in list format.

PS C:\> (Get-Item C:\Windows\explorer.exe).VersionInfo | format-list

OriginalFilename  : EXPLORER.EXE.MUI
FileDescription   : Windows Explorer
ProductName       : Microsoft® Windows® Operating System
Comments          :
CompanyName       : Microsoft Corporation
FileName          : C:\Windows\explorer.exe
FileVersion       : 10.0.15063.0 (WinBuild.160101.0800)
ProductVersion    : 10.0.15063.0
IsDebug           : False
IsPatched         : False
IsPreRelease      : False
IsPrivateBuild    : False
IsSpecialBuild    : False
Language          : English (United States)
LegalCopyright    : © Microsoft Corporation. All rights reserved.
LegalTrademarks   :
PrivateBuild      :
SpecialBuild      :
FileVersionRaw    : 10.0.15063.608
ProductVersionRaw : 10.0.15063.608

PS C:\>

[ More Info ]

[/os/windows/PowerShell] permanent link

Sun, Oct 08, 2017 10:57 pm

Calculating file checksums on an OS X system

If you need to calculate a checksum, aka cryptographic hash value or digital fingerprint, on a Mac OS X system, you can use the md5 command to calculate a MD5 checksum, which is equivalent to the md5sum utility on Linux systems, and the shasum command to calculate Secure Hash Algorithms (SHA). The default value for shasum, if no algorithm is specified, is Secure Hash Algorithm 1 (SHA-1), but you can specify other algorithms, such as Secure Hash Algorithm 2 (SHA-2), e.g. SHA-256, using the -a option. E.g. -a 256 for SHA-256.

[ More Info ]

[/os/os-x] permanent link

Sat, Oct 07, 2017 10:59 pm

Determining the day of year value using Python

I sometimes need to determine the day of the year corresponding to today's date. The day of year starts with January 1 as day 1 and for 2017, December 31 is day 365. You can find sites online that will provide those values, e.g. Day Numbers for 2017 or NOAA's DOY Calendar. Or, on a system with Python installed, e.g., Linux or OS X, you can use the datetime module to obtain the day of the year corresponding to the current date as shown below:

$ python
Python 2.7.10 (default, Oct 23 2015, 19:19:21) 
[GCC 4.2.1 Compatible Apple LLVM 7.0.0 (clang-700.0.59.5)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import datetime
>>> exit()

Since today is October 7 of the year 2017, the day of the year is 280.

If you want to obtain the day of year (DOY) for another date, you can use, month, day).timetuple().tm_yday where year is the relevant year, month is the month, and day is the day of interest. E.g., March 1, 2017 is DOY 60:

>>> import datetime
>>>, 3, 1).timetuple().tm_yday

[/languages/python] permanent link

Fri, Oct 06, 2017 11:15 pm

Viewing DHCP information on an OS X system

If you want to determine the IP address of the DHCP server from which a Mac OS X system received its IP address, subnet mask, etc., you can obtain that information from a command-line interface (CLI), i.e., a Terminal window by using the command ipconfig getpacket interface where interface is the relevant network interface, which will usually be en0 or en1. You can issue the command ifconfig -a in a Terminal window to see the network interfaces on the system and which have IP addresses assigned to them.

getpacket interface-name
Prints to standard output the DHCP/BOOTP packet that the client accepted from the DHCP/BOOTP server. This command is useful to check what the server provided, and whether the values are sensible. This command outputs nothing if DHCP/BOOTP is not active on the interface, or the attempt to acquire an IP address was unsuccessful.

[ More Info ]

[/os/os-x] permanent link

Sun, Oct 01, 2017 10:53 pm

Finding Gmail SMTP entries in Sendmail log files

I wanted to determine how many connections I was receiving per day from Gmail Simple Mail Transfer Protocol (SMTP) servers to my email server running Sendmail on a CentOS Linux system and the IP addresses of the Gmail servers that were sending email to users on my server. So I created a simple Python script to search for lines in the maillog file, /var/log/maillog for any lines containing "relay" and "" on the same line, since the Gmail servers are in Google's domain.

[ More Info ]

[/languages/python] permanent link

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