Powershell-在从IP，FQDN和主机名创建变量并使用它们来ping之前，从hosts文件的每一行中删除所有空格

Question

Say we have a hosts file of:

10.10.10.10    test1.domain test1
20.20.20.201   test2.domain test2
30.30.301.30   test3.domain test3
40.40.40.40    test4.domain test4

Note the IPs with 3 digits in the host identifier, with this in mind, each line is structured slightly differently, in that those with the 2 digits, have more spaces between the IP and the FQDN. Bearing in mind these differences, how would one either: 1. extract the FQDN from each line & ping as you go through each line OR 2. strip out the IP altogether and then loop through each entry, pinging each FQDN as you go?

I can't seem to do option 1, and the closest to option 2 I have got is by doing this:

Get-Content hosts | ForEach-Object { $_Split()[3]; }

But this only prints out those hosts where there is 3 digits in the host identifier, whilst those with 2 digits have more whitespace between the IP and FQDN, therefore it counts the FQDN as being on the 4th field.

Can anyone assist with this please? I am fairly new to PowerShell coming from a UNIX background.

Answer 1

Strings in Powershell are .Net String objects and thus contain powerful manipulation methods. Split() can be told to omit empty elements. Like so,

# Read host list
$data = Get-Content C:\Temp\hostlist.txt
# Split each row from the file. Use space to split, omit empty elements
# Thus element 0 is the IP, 1 is the FQDN, 2 is the hostname
$data | ForEach-Object { ($_.split(" ", [StringSplitOptions]::RemoveEmptyEntries))[1] }

# Output
test1.domain
test2.domain
test3.domain
test4.domain