How do I add timestamps to individual lines of PowerShell & output?

Question

How, if at all, is it possible to add timestamps to each line of an output generated by the & PowerShell operator?

Example:

PS H:\> $result = & ping 192.168.1.1 PS H:\> echo $result  Pinging 192.168.1.1 with 32 bytes of data: Reply from 192.168.1.1: bytes=32 time=104ms TTL=250 Reply from 192.168.1.1: bytes=32 time=106ms TTL=250 Reply from 192.168.1.1: bytes=32 time=102ms TTL=250 Reply from 192.168.1.1: bytes=32 time=102ms TTL=250 Ping statistics for 192.168.1.1: Packets: Sent = 4, Received = 4, Lost = 0 (0% loss), Approximate round trip times in milli-seconds: Minimum = 102ms, Maximum = 106ms, Average = 103ms 

Desired result:

PS H:\> echo $result  2014-12-08T14:45:48.8898125+00:00:Pinging 192.168.1.1 with 32 bytes of data: 2014-12-08T14:45:48.8932661+00:00:Reply from 192.168.1.1: bytes=32 time=104ms TTL=250 2014-12-08T14:45:48.9233451+00:00:Reply from 192.168.1.1: bytes=32 time=106ms TTL=250 2014-12-08T14:45:48.9765438+00:00:Reply from 192.168.1.1: bytes=32 time=102ms TTL=250 2014-12-08T14:45:49.0233105+00:00:Reply from 192.168.1.1: bytes=32 time=102ms TTL=250 2014-12-08T14:45:49.0233201+00:00: 2014-12-08T14:45:49.0238753+00:00:Ping statistics for 192.168.1.1: 2014-12-08T14:45:49.0239210+00:00:    Packets: Sent = 4, Received = 4, Lost = 0 (0% loss), 2014-12-08T14:45:49.0233318+00:00:Approximate round trip times in milli-seconds: 2014-12-08T14:45:49.0237209+00:00:    Minimum = 102ms, Maximum = 106ms, Average = 103ms 

I know how to split / join a PowerShell array, but this can only happen AFTER the & operator completes. I am looking for more realtime-like solution, where timestamps are added to the output while the & operator is running.

By the way, the timestamp itself is $($(Get-Date -Format o) + ":")

Answer 1

You could use a filter:

filter timestamp {"$(Get-Date -Format o): $_"} $result = & ping 192.168.1.1 | timestamp 

Sample output from $result:

2014-12-08T11:42:59.2827202-05:00:  2014-12-08T11:42:59.2857205-05:00: Pinging 192.168.1.1 with 32 bytes of data: 2014-12-08T11:43:03.1241043-05:00: Request timed out. 2014-12-08T11:43:08.1236042-05:00: Request timed out. 2014-12-08T11:43:13.1241042-05:00: Request timed out. 2014-12-08T11:43:18.1246042-05:00: Request timed out. 2014-12-08T11:43:18.1246042-05:00:  2014-12-08T11:43:18.1246042-05:00: Ping statistics for 192.168.1.1: 2014-12-08T11:43:18.1246042-05:00:     Packets: Sent = 4, Received = 0, Lost = 4 (100% loss), 

Answer 2

For anyone that is looking for more information on filter, here is the documentation. It was surprising difficult to find since searching any combination of the word "filter" and "powershell" will give a million examples and no documentation. Also help filter in powershell provides no obvious help either.

The answer provided by mjolinor is the best way to do something like this, but I wanted to expand on it.

filter timestamp {"$(Get-Date): $_"} 

Is a shortcut for calling this

function timestamp { Process{"$(Get-Date): $_"} } 

Both of these create named functions that accept input from the pipeline. Run help pipline in powershell to learn more. The pipeline will operate on a single object at a time, and that object can be referred to with the automatic variable $_. So each function will iterate over every item in the pipeline that was piped to it using the | pipe character.

This behaves differently than a normal function in that it's working on the objects as they arrive, instead of all at once. For example running

function timestamp {         "$(Get-Date): $input" } $result = & ping 127.0.0.1 $result | timestamp 

Would dump the entire $result object on a single line and result in a response that looks like this

03/14/2018 15:23:16:  Pinging 127.0.0.1 with 32 bytes of data: Reply from 127.0.0.1: b ytes=32 time<1ms TTL=128 Reply from 127.0.0.1: bytes=32 time<1ms TTL=128 Reply from 12 7.0.0.1: bytes=32 time<1ms TTL=128 Reply from 127.0.0.1: bytes=32 time<1ms TTL=128  Pi ng statistics for 127.0.0.1:     Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),  Approximate round trip times in milli-seconds:     Minimum = 0ms, Maximum = 0ms, Avera ge = 0ms 

Since the function is operating on the object as a whole you would have to iterate over each line. Changing it to this

function timestampfunction {     foreach ($i in $input){         "$(Get-Date): $i"     } } 

Would give you the nicely formatted

03/14/2018 15:23:16:  03/14/2018 15:23:16: Pinging 127.0.0.1 with 32 bytes of data: 03/14/2018 15:23:16: Reply from 127.0.0.1: bytes=32 time<1ms TTL=128 03/14/2018 15:23:16: Reply from 127.0.0.1: bytes=32 time<1ms TTL=128 03/14/2018 15:23:16: Reply from 127.0.0.1: bytes=32 time<1ms TTL=128 03/14/2018 15:23:16: Reply from 127.0.0.1: bytes=32 time<1ms TTL=128 03/14/2018 15:23:16:  03/14/2018 15:23:16: Ping statistics for 127.0.0.1: 03/14/2018 15:23:16:     Packets: Sent = 4, Received = 4, Lost = 0 (0% loss), 03/14/2018 15:23:16: Approximate round trip times in milli-seconds: 03/14/2018 15:23:16:     Minimum = 0ms, Maximum = 0ms, Average = 0ms 

Here is a nicely written article on the differences between these approaches.