Write-Host and Write-Output

Good to remember:

1. Write-Host converts the object to a string representation and then outputs it to the host (console). There’s two things to keep in mind here: (1) the output bypasses any pipelines etc and is sent directly to the host; (2) the object is converted to a string representation, using the toString() method (which is present in all classes), and so the string representation may not necessarily be what you expect.

   Case in hand:

   # define a hash table PS> $table = @{ a = 1; b = 2 } # use write-host to output it. notice the output. PS> write-host $table System.Collections.DictionaryEntry System.Collections.DictionaryEntry # enumerate the hash table and find the type of each element in it # notice the type name - it matches what we saw above PS> $table.GetEnumerator() | %{ $_ | Get-Member } TypeName: System.Collections.DictionaryEntry Name MemberType Definition ---- ---------- ---------- Name AliasProperty Name = Key Equals Method bool Equals(System.Object obj) GetHashCode Method int GetHashCode() GetType Method type GetType() ToString Method string ToString() Key Property System.Object Key {get;set;} Value Property System.Object Value {get;set;} Name AliasProperty Name = Key Equals Method bool Equals(System.Object obj) GetHashCode Method int GetHashCode() GetType Method type GetType() ToString Method string ToString() Key Property System.Object Key {get;set;} Value Property System.Object Value {get;set;} # notice what happens if we were to convert the hash table to a string directly PS> "$table" System.Collections.Hashtable # now run the toString() method of that table and notice it's same as above PS> $table.ToString() System.Collections.Hashtable

   1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39

   # define a hash table PS> $table = @{ a = 1; b = 2 }   # use write-host to output it. notice the output. PS> write-host $table System.Collections.DictionaryEntry System.Collections.DictionaryEntry   # enumerate the hash table and find the type of each element in it # notice the type name - it matches what we saw above PS> $table.GetEnumerator() | %{ $_ | Get-Member }        TypeName: System.Collections.DictionaryEntry   Name        MemberType    Definition ----        ----------    ---------- Name        AliasProperty Name = Key Equals      Method        bool Equals(System.Object obj) GetHashCode Method        int GetHashCode() GetType     Method        type GetType() ToString    Method        string ToString() Key         Property      System.Object Key {get;set;} Value       Property      System.Object Value {get;set;} Name        AliasProperty Name = Key Equals      Method        bool Equals(System.Object obj) GetHashCode Method        int GetHashCode() GetType     Method        type GetType() ToString    Method        string ToString() Key         Property      System.Object Key {get;set;} Value       Property      System.Object Value {get;set;}     # notice what happens if we were to convert the hash table to a string directly PS> "$table" System.Collections.Hashtable   # now run the toString() method of that table and notice it's same as above PS> $table.ToString() System.Collections.Hashtable

2. Write-Output is better in the sense that (1) it only passes the output to the next step of the pipeline (or to the host if we are at the end of the pipeline) and (2) no conversion happens, the object is output and formatted as it is.

   To give an example with the previously created table:

   PS> Write-Output $table Name Value ---- ----- a 1 b 2

   1 2 3 4 5 6

   PS> Write-Output $table   Name                           Value ----                           ----- a                              1 b                              2

   This is same as if you were to output the object directly:

   PS> $table Name Value ---- ----- a 1 b 2

   1 2 3 4 5 6

   PS> $table   Name                           Value ----                           ----- a                              1 b                              2

   As previously mentioned the formatting of such output depends the ps1xml defintions for that object.