Fastest way to find strings in a file

Question

I have a log file that is not more than 10KB (File size can go up to 2 MB max) and I want to find if atleast one group of these strings occurs in the files. These strings will be on different lines like,

ACTION:.......

INPUT:...........

RESULT:..........

I need to know atleast if one group of above exists in the file. And I have do this about 100 times for a test (each time log is different, so I have reload and read the log), so I am looking for fastest and bets way to do this.

I looked up in the forums for finding the fastest way, but I dont think my file is too big for those silutions.

Thansk for looking.

Answer 1

I would read it line by line and check the conditions. Once you have seen a group you can quit. This way you don't need to read the whole file into memory. Like this:

    public bool ContainsGroup(string file)
    {
        using (var reader = new StreamReader(file))
        {
            var hasAction = false;
            var hasInput = false;
            var hasResult = false;
            while (!reader.EndOfStream)
            {
                var line = reader.ReadLine();
                if (!hasAction)
                {
                    if (line.StartsWith("ACTION:"))
                        hasAction = true;
                }
                else if (!hasInput)
                {
                    if (line.StartsWith("INPUT:"))
                        hasInput = true;
                }
                else if (!hasResult)
                {
                    if (line.StartsWith("RESULT:"))
                        hasResult = true;
                }

                if (hasAction && hasInput && hasResult)
                    return true;
            }
            return false;
        }
    }

This code checks if there is a line starting with ACTION then one with INPUT and then one with RESULT. If the order of those is not important then you can omit the if () else if () checks. In case the line does not start with the strings replace StartsWith with Contains.

Answer 2

Here's one possible way to do it:

StreamReader sr;
string fileContents;

string[] logFiles = Directory.GetFiles(@"C:\Logs");

foreach (string file in logFiles)
{

    using (StreamReader sr = new StreamReader(file))
    {

        fileContents = sr.ReadAllText();

        if (fileContents.Contains("ACTION:") || fileContents.Contains("INPUT:") || fileContents.Contains("RESULT:"))
        {
             // Do what you need to here
        }

    }
}

You may need to do some variation based on your exact implementation needs - for example, what if the word spans two lines, does the line need to start with the word, etc.

Added

Alternate line-by-line check:

StreamReader sr;
string[] lines;

string[] logFiles = Directory.GetFiles(@"C:\Logs");

foreach (string file in logFiles)
{

    using (StreamReader sr = new StreamReader(file)
    {

        lines = sr.ReadAllLines();

        foreach (string line in lines)
        {        
            if (line.Contains("ACTION:") || line.Contains("INPUT:") || line.Contains("RESULT:"))
            {
                // Do what you need to here
            }
        }

    }
}