On our PowerShell community forums, we have recently received questions asking if it is possible to store PowerShell variables in external files, and if so, how is it done. It is indeed possible to store variables in external files for PowerShell to use. These external variables can be stored in a variety of file types. Storing them in a PowerShell file is one of the easiest because you can just dot source these files.<\/p>\n
We will cover the following methods to store variables:<\/p>\n
\n\n
- Script Files<\/strong><\/li>\n
- Text Files<\/strong><\/li>\n
- JSON Files<\/strong><\/li>\n
- XML Files<\/strong><\/li>\n<\/ul>\n<\/blockquote>\n
The examples shown in this post are pretty simple, but that doesn\u2019t mean that it isn’t possible to store fairly complex variables in external files. If you want to\u00a0experiment with storing external variables you can download the sample files for this post\u00a0here<\/a>.<\/p>\n
Script Files<\/strong><\/span><\/p>\n
Dot sourcing may be the easiest way to store external variables\u2014but it isn’t always the safest. When a file is dot sourced we are telling PowerShell to execute that script. If there is any malicious code in the file, then that code will also run.<\/p>\n
In addtion to dot sourcing, you will also need to ensure that the external variables PowerShell script is signed and that\u00a0Remote Execution<\/a> is enabled on your machine.<\/p>\n
Dot sourcing can be helpful if we need to get information about something dynamically. For the other options discussed in this post, the data stored in the file types will have to be manually changed.<\/p>\n
\n\n\n
\n \n 1\r\n2\r\n3\r\n4<\/pre>\n<\/td>\n\n # Here we dot source the External variables PowerShell File\r\n. \"C:\\Test\\BlogPosts\\ExternalVariables.ps1\"\r\n\r\nWrite-Host $External_Variable1 $External_Variable2<\/pre>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n\n<\/div>\n
Here is what is in the ExternalVariables.ps1 file:<\/p>\n
#Declaration of External variables
\n$External_Variable1 = ‘Sapien’
\n$External_Variable2 = ‘Technologies’<\/p><\/blockquote>\nText Files<\/strong><\/span><\/p>\n
External variables can also be stored in a number of text files and formats, such as plain text in a general .txt file using the Get-Content <\/b><\/em>cmdlet. When we import variables this way, we aren\u2019t running any code, so it\u2019s not a problem if you don\u2019t constantly monitor the files to get information.<\/p>\n
The following three pictures are examples of different ways of storing information in a simple text file:<\/p>\n
\n\n\n
\n \n 1\r\n2\r\n3\r\n4\r\n5\r\n6\r\n7\r\n8\r\n9\r\n10\r\n11\r\n12\r\n13<\/pre>\n<\/td>\n\n $ScriptDir = Split-Path $script:MyInvocation.MyCommand.Path\r\n$ScriptDir += \"\\ExternalVariables.txt\"\r\n\r\n# Use get content to get all of the lines that are in the txt files\r\n\r\n$External_Variables = Get-Content -Path $ScriptDir\r\n\r\n#The Information from the ExternalVariables comes in as an array \r\n#So to print all of the strings in $program we use a foreach loop\r\nforeach ($string in $External_Variables)\r\n{\r\n\tWrite-Host $string\t\r\n}<\/pre>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n\n<\/div>\n
Here is what is in the ExternalVariables.txt file:<\/p>\n
“PowerShell Studio”
\n“PrimalScript”
\n“Version Recall”<\/p><\/blockquote>\nJust like an array, we can store hash tables in text files. To get our hash table from a text file, we will have to pipe the output of the Get-Content<\/b><\/em> to the ConvertFrom-StringData<\/b><\/em>\u00a0cmdlet to convert the output into a hash table.<\/p>\n
\n\n\n
\n \n 1\r\n2\r\n3\r\n4\r\n5\r\n6\r\n7\r\n8\r\n9\r\n10\r\n11\r\n12\r\n13\r\n14<\/pre>\n<\/td>\n\n $ScriptDir = Split-Path $script:MyInvocation.MyCommand.Path\r\n$ScriptDir += \"\\ExternalVariablesHashTable.txt\"\r\n# Getting the contents of the External Variable text file\r\n# This file is store in plan text and is not in any special format\r\n\r\n# We use the \"raw\" parameter here in Get-Content so that when we get the contents\r\n# of the file so that our hashtable is not converted to an object\r\n$program = Get-Content -raw -Path $ScriptDir | ConvertFrom-StringData\r\n\r\nwrite-host \"`nType of the variable `$program`n\"\r\n$program.GetType()\r\n\r\nwrite-host \"`nPrinting `$program\" \r\n$program<\/pre>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n\n<\/div>\n
Here is what is in ExternalVariablesHashTable.txt:<\/p>\n
Company=Sapien Technologies
\nProduct=PowerShell Studio<\/p><\/blockquote>\nStoring information in a text file like this is a convenient way to keep information in a human-readable format. Text files also come with the benefit of not being executable, so if there happens to be malicious code stored in a file you don\u2019t regularly manage it won’t be executed.<\/span><\/span>
\n<\/span><\/span><\/p>\nJSON File<\/strong><\/span><\/p>\n
It is also possible to store external variables in a JSON format. The only caveat being that we will need to once again pipe the output of Get-Content<\/em><\/strong> to another cmdlet; however this time it\u2019s ConvertFrom-Json<\/em><\/strong> rather than ConvertFrom-StringData<\/em><\/strong>. For those unfamiliar with JSON or need to brush up on the format, please visit www.JSON.org<\/a>.<\/p>\n
\n\n\n
\n \n 1\r\n2\r\n3\r\n4\r\n5\r\n6\r\n7\r\n8\r\n9\r\n10\r\n11\r\n12\r\n13\r\n14\r\n15\r\n16\r\n17<\/pre>\n<\/td>\n\n $ScriptDir = Split-Path $script:MyInvocation.MyCommand.Path\r\n$ScriptDir += \"\\jsonfile.json\"\r\n#Getting information from the json file\r\n#The we pass the output from Get-Content to ConvertFrom-Json Cmdlet\r\n$JsonObject = Get-Content $ScriptDir | ConvertFrom-Json\r\n\r\n#Right now we have an array which means that we have to index\r\n#an element to use it\r\n$JsonObject.Users[0]\r\n\r\n#When indexed we can call the attributes of the elements\r\nWrite-Host \"Attributes individually printed\"\r\n$JsonObject.Users[0].Name\r\n$JsonObject.Users[0].Age\r\n$JsonObject.Users[0].City\r\n$JsonObject.Users[0].Country\r\n$JsonObject.Users[0].UserId<\/pre>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n\n<\/div>\n
Here is what is in the JSON File:<\/p>\n
{
\n“Users”: [{
\nName:”John Smith”,
\nAge:”35″,
\nCity:”San Francisco”,
\nCountry:”USA”,
\nUserId:”52917″
\n},
\n{
\nName:”Jane Wellington”,
\nAge:”28″,
\nCity:”Seattle”,
\nCountry:”USA”,
\nUserId:”25589″
\n},
\n{
\nName:”Samantha Scott”,
\nAge:”33″,
\nCity:”Los Angeles”,
\nCountry:”USA”,
\nUserId:”11564″
\n}
\n]
\n}<\/p><\/blockquote>\n