选择字符串适用于多行输入

Question

I have a file like:

abc WANT THIS
def NOT THIS
ghijk WANT THIS
lmno DO NOT LIKE
 pqr WANT THIS
...

From which I want to extract:

abc
ghijk
pqr

When I apply the following:

(Select-String -Path $infile -Pattern "([^ ]+) WANT THIS").Matches.Groups[1].Value >$outfile

It only returns the match for the first line:

abc

(adding -AllMatches did not change the behaviour)

Answer 1

You may use

Select-String -path $infile -Pattern '^\s*(\S+) WANT THIS' -AllMatches | Foreach-Object {$_.Matches} | Foreach-Object {$_.Groups[1].Value} > $outfile

The ^\\s*(\\S+) WANT THIS pattern will match

• ^ - start of a line
• \\s* - 0+ whitespaces
• (\\S+) - Group 1: one or more non-whitespace chars
• WANT THIS - a literal substring.

Now, -AllMatches will collect all matches, then, you need to iterate over all matches with Foreach-Object {$_.Matches} and access Group 1 values (with Foreach-Object {$_.Groups[1].Value} ), and then save the results to the output file.

Answer 2

Re-reading the code, its matching them all, but only writing the value of the first match (doh!):

 (Select-String -Path $scriptfile -Pattern "([^ ]+)  WANT THIS").Matches.Groups.Value >$tmpfile

OTOH, it appears that the "captures" in the pattern output object also contain the "non-captured" content!!!!