10.2 Working with the default formatting
默认的格式在.format.ps1xml文件里。比如关于process对象的格式在 DotNetTypes.format.ps1xml 文件里，我们可以使用如下命令查看该文件：
PS C:\>cd $pshome
PS C:\>notepad dotnettypes.format.ps1xml要找到某一具体对象的格式规则，我们得知道该对象的类型以及其对应的格式文件。比如对于 get-process 这个命令的输出格式，我们使用 get-process | gm 查看其类型，然后复制其类型 System.Diagnostics.Process ，然后在刚刚打开的文件中搜索 System.Diagnostics.Process 。注意，搜索到的第一个可能是一个 ProcessModule 对象，而不是我们想要的 Process 对象，我们要找到的是 Process 对象。
当我们运行 Get-Process cmdlet的时候，会发生如下事情：
1. cmdlet将对象的类型 System.Diagnostics.Process 放入pipeline中。
2. 在pipeline的结尾处，有一个隐藏的cmdlet Out-Default ，它的任务是接受pipeline中的对象。
3. Out-Default 将对象传给 Out-Host
4. 大多数 Out- 开头的cmdlet没有处理标准对象的能，他们的任务是将对象送给格式化系统。
5. 格式化系统查看对象的类型，遵循一套内置的格式化规则来产生格式化指令，然后将这指令传给 Out-Host
6. Out-Host 收到这些指令的时候，就会按照这些指令在屏幕上构造输出的排版。
上述也会发生在我们人为定义 Out- cmdlet的时候。比如 Get-Process | Out-File procs.txt 就是将 Out-Host 换成 Out-File
第5步中的标准化规则有三个，系统会逐个尝试，直到成功找到。
1. first formatting rule：The system looks to see whether the type of object it’s dealing with has a predefined view.
2. second formatting rule：It looks to see whether anyone has declared a default display property set for that type of object.
3. third formatting rule：is about the kind of output to create.If the formatting system displa
ys four or fewer properties, it uses a table. If there are five or more properties, it uses a list.
比如 Get-WmiObject Win32_OperatingSystem 产生的对象类型是 System.Management.ManagementObject#root\cimv2\Win32_OperatingSystem ，我们在所有 .format.ps1xml 中搜索 Win32_OperatingSystem 都不会找到预定义的视图。这时，系统会使用 the second formatting rule ，发现此对象可以在 Types.ps1xml 中找到。
PowerShell共有四个关于格式化的cmdlet，它们分别如下：
10.3 Formatting tables
首先是 Format-Table 别名 Ft
10.4 Formatting lists
Sometimes you need to display more information than will fit horizontally in a table, which can make a list useful. Format-List is the cmdlet you’ll turn to, or you can use its alias, Fl
10.5 Formatting wide lists
The last cmdlet,
Format-Wide(or its alias,Fw), displays a wide list. It’s able to display only the values of a single property, so its-propertyparameter accepts only one property name, not a list, and it can’t accept wildcards.
By default,Format-Widelooks for an object’sNameproperty, becauseNameis a commonly used property and usually contains useful information. The display generally defaults to two columns, but a-columnsparameter can be used to specify more columns:Get-Process | Format-Wide name -col 4
.
最后一个cmdlet 是Format-Custom
Format-Customis mainly used to display various predefined custom views.
10.7 Going out: to a file, a printer, or the host
If a command line ends in a
Format-cmdlet, the formatting instructions created by theFormat-cmdlet go toOut-Default, which forwards them toOut-Host, which displays them on the screen:
Get-Service | Format-Wide
You could also manually pipe the formatting instructions toOut-Host, which accomplishes exactly the same thing:
Get-Service | Format-Wide | Out-Host
Alternatively, you can pipe formatting instructions to eitherOut-FileorOut-Printerto direct formatted output to a file or to hard copy.扫描二维码关注公众号，回复： 3207048 查看本文章
10.8 Another out: GridViews
Out-GridView 绕过了格式化子系统。
Out-GridView can’t receive the output of a Format- cmdlet—it can receive only the regular objects output by other cmdlets.
10.9 Common points of confusion
10.9.1 Always format right
Your
Format-cmdlet should be the last thing on the command line, withOut-FileorOut-Printeras the only exceptions.
10.9.2 One type of object at a time, please
The next thing to avoid is putting multiple kinds of objects into the pipeline.
因此运行Get-Process; Get-Service是不可取的