12/28/2023 0 Comments Powershell grep files for stringThe total milliseconds elapsed was used as the time measure. (You can download the resulting test files here: grep-select-string-test.zip).Įach search was performed seven times. There were eleven sample files: 1,000 sentences, 10,000 sentences, 20,000 sentences, and so on to 100,000 sentences. One in ten sentences contained the word “key” at a random location within the sentence. Each file contained sentences of random length (5-25 random words). I generated sample files using a sample dictionary file. I do have the occassional free weekend and I was very curious. If Select-String was significantly slower, then a good weekend project might be to write a faster parser. Mark Boltz ( suggested running several tests of both and taking an average to get a sense of how Select-String stacks up. NET, we can make an assumption that grep should be faster than Select-String. Richard Minerich ( brought up a good point: compiled C code is generally faster than C# code. This had me wondering about how PowerShell’s Select-String stacks up. #2 trick: GNU grep is fast because it EXECUTES VERY FEW INSTRUCTIONS FOR EACH BYTE that it *does* look at.” “The key to making programs fast is to make them do practically nothing.” He also provided this excellent advice: “#1 trick: GNU grep is fast because it AVOIDS LOOKING AT EVERY INPUT BYTE. In the post titled “ why GNU grep is fast“, Mike described the algorithm grep uses. ![]() Mike was the original developer of GNU grep. Over the weekend, we were discussing on Twitter a post from Mike Haertel. Of course, various functions exist that enable you to modify the found substrings.How fast is grep? Reasonably fast. One example would be to format the output in a much easier-to-read layout by piping the result into Format-List or Out-GridView. String processing of matchesīecause you can pass the result of Select-String to a variety of cmdlets, you have almost unlimited possibilities to process the results. ![]() ![]() To get all matches, you have to add the -AllMatches switch. The example below shows the exact matches: Select-String -Path *.* -Pattern "DO.*=" | Select Matchesīy default, you only see the first match in each line. With complex regular expressions, you are often uncertain about the strings they actually match. If you work with regular expressions, Matches is another particularly helpful property. (The parameter -Context also displays lines before and after the line with the match.)įor example, the command below only displays filenames and lines that contain the search string: Select-String -Path index.html -SimpleMatch "Home" | Select FileName, LineNumber Usage of MatchInfo propertiesįor instance, properties are useful for changing the output of the cmdlet if you are unhappy with the relatively confusing presentation of path, filename, and line number of Select-String. If you pass the output of Select-String to Get-Member, you’ll receive a list of all methods and properties. Compared to flat text, objects have the advantage of offering methods and properties that allow you to process their output in a more sophisticated way. Search results as MatchInfo objectsĪs opposed to text-oriented tools such as find, a cmdlet returns an object (in the case of Select-String of the type MatchInfo). However, you can accomplish this by piping the output of the Get-ChildItem cmdlet into Select-String: Get-ChildItem *.* -Exclude *.pdf -Recurse | Select-String -Pattern "DO.*="īecause Get-ChildItem selects the files, Select-String only has to take care of the search pattern. In contrast to find and findstr, Select-String cannot search recursively in subdirectories. In the above example, Select-String searches only in files in the current directory, excluding ZIP archives and PDF files. ![]() You may further restrict your search by excluding files with the parameter -Path, together with wildcards: Select-String -Path *.* -Exclude *.pdf,*.zip -Pattern "DO.*=" -NotMatch Search in subdirectories with Get-ChildItem With -NotMatch, PowerShell’s grep counterpart Select-String also supports reverse search, which finds only lines that don’t contain the search pattern. Select-String -Path index.html -SimpleMatch "Home" Reverse search with -NotMatch
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |