从Powershell中的外部命令输出中提取模式

Question

For my powershell script, I run an external command and look for a specific pattern in the output. For example:

The command "eraseDevice" gives me output like this:

Erasing Deployment... Erasing sector 0x080a8000 
Erasing sector 0x080c1000 
Erasing sector 0x080e1000 
Erasing sector 0x64010000 
Rebooting... 

I want the number 0x080a8000 from this output. I have tried the following:

eraseDevice | select-string -simplematch -pattern 0x 

which returns the lines that contain the hexadecimal number. I tried doing the following as well, but all of them return errors:

eraseDevice | select-string -simplematch -pattern 0x -totalcount 1 
eraseDevice | (select-string -simplematch -pattern 0x)[4] 
eraseDevice | (select-string -simplematch -pattern 0x).split()[4] 

0x080a8000 from the first line. Thanks for your help.

Answer 1

You can use Select-Object to get only the first line of output from eraseDevice :

eraseDevice | Select-Object -First 1;

Then pipe that into Select-String to find '0x' followed by exactly eight hexadecimal characters:

eraseDevice | Select-Object -First 1 | Select-String -Pattern '0x[0-9a-f]{8}'

Select-String returns instances of the MatchInfo class . To retrieve just the matched number, access the Value property of the first element of the Matches collection:

eraseDevice `
    | Select-Object -First 1 `
    | Select-String -Pattern '0x[0-9a-f]{8}' `
    | ForEach-Object { $_.Matches[0].Value };

Note that if you did want to extract the sector number from all lines of output, you could just remove Select-Object from the pipeline and leave the rest of the command unmodified.

Answer 2

$r = [regex] "(0x[0-9a-f]+)"
$line = (eraseDevice | select -first 1)
$num = $r.match($line).groups[1].value