How to use string.format with string array in powershell

Question

I want to output a formated string to console. I have one string variable and one string array variable.

When I do this:

$arr = "aaa","bbb"
"test {0} + {1}" -f "first",$arr

The output is this:

test first + System.Object[]

But I need output to be:

test first + aaa,bbb

Or something similar...

Answer 1

Several options:

1. Join the array first, so you don't rely on the default ToString() implementation (which just prints the class name):

   PS> 'test {0} + {1}' -f 'first',($arr -join ',')
   test first + aaa,bbb
   

2. Use string interpolation:

   PS> $first = 'first'
   PS> "test $first + $arr"
   test first + aaa bbb
   

   You can change the delimiter used by setting $OFS, which by default is a space:

   PS> $OFS = ','
   PS> "test $first + $arr"
   test first + aaa,bbb
   

3. You can get the same result (including the note about $OFS) with

   PS> 'test {0} + {1}' -f 'first',(''+$arr)
   test first + aaa bbb
   

   This forces the array to be converted into a single string first, too.