I wondering if there is a way to monitor a .txt file without locking it and have the newly appended lines parsed in order to be sent to a database.
I know FileSystemWatcher will monitor the txt file without locking it and notify me if a change has occurred. The problem is that it does not tell the lines of data that has been appended. All of the examples I have looked at exclude the part of displaying newly appended lines or doing any processing of the new data. My program has the following structure:
static void Main(string[] args)
{
//string line;
//createWatcher (FileSystemWatcher)
foreach (string line in getLines(#"C://Documents/log.txt"))
{
string teststring = line;
string[] parts = line.Split(' ', ',', '-', '>', '[', ']');
StringBuilder builder = new StringBuilder();
foreach (string h in parts)
{
builder.Append(h).Append(" ");
}
string result = builder.ToString();
string cleanedString = System.Text.RegularExpressions.Regex.Replace(result, #"\s+", " ");
string trimString = cleanedString.Trim();
trimString = trimString.Remove(trimString.Length - 7);
//Console.WriteLine(trimString);
//Process new lines (parse/split)
//Connect and send to database
}
}
So my objective is to monitor a .txt file without locking it.
Read this file for existing data, and wait for appended data.
I then want to parse this data and send it to a database.
Does anyone know how to best approach this? or have a good tutorial?
Your best bet is for the code fired off of the file system watcher to keep track of the Position in the stream that's reading the file. Here's some pseudocode:
if(no stored position)
start at beginning of file
else
{
streamOfFile.Seek(storedPosition)
read until end of file
store stream.Postition
}
This could be done by tracking the length of the file the last time you read it, and then starting from that point next time. However, there are lots of race conditions around this since you're potentially reading from a file at the same time as the OS is writing.
Isn't your bigger problem that you can't guarantee that the only change to the file is an append? What happens if I insert a line at the top of the file, or replace the whole thing?
Related
I want to get the line containing a certain word that cannot be repeated like profile ID without make loop to read each of line separately, Because if the word I am looking for is in the last line of the text file, this will take a lot of time to get it, and if the search process is for more than one word and extract the line that contains it, I think it will take a lot of time.
Example for line text file
name,id,image,age,place,link
string word = "13215646";
string output = string.Empty;
using (var fileStream = File.OpenRead(FileName))
using (var streamReader = new StreamReader(fileStream, Encoding.UTF8))
{
String line;
while ((line = streamReader.ReadLine()) != null)
{
string[] strList = line.Split(',');
if (word == strList[1]) // check if word = id
{
output = line;
break;
}
}
}
You can use this to search the file:
var output = File.ReadLines(FileName).
Where(line => line.Split(',')[1] == word).
FirstOrDefault();
But it won't solve this:
if the word I am looking for is in the last line of the text file, this will take a lot of time to get it, and if the search process is for more than one word and extract the line that contains it, I think it will take a lot of time.
There's not a practical way to avoid this for a basic file.
The only ways around actually reading through the file is either maintaining an index, which requires absolute control over everything that might write into the file, or if you can guarantee the file is already sorted by the columns that matter, in which case you can do something like a binary search.
But neither is likely for a random csv file. This is one of the reasons people use databases.
However, we also need to stop and check whether this is really a problem for you. I'd expect the code above to handle files up to a couple hundred MB in around 1 to 2 seconds on modern hardware, even if you need to look through the whole file.
You can optimise the code. Here are few ideas:
var ids = new ["13215646", "113"];
foreach(var line in File.ReadLines(FileName))
{
var id = line.Split(',', count: 3)[1]; // Optimization 1: Use: `count: 3`
if(ids.Contains(id) // Optimization 2: Search for multiple ids
{
//Do what you need with the line
}
}
I am trying to read a CSV file and stored all the values in the single list.CSV file contains credentials as uid(userid) and pass(password) and separated by','I have successfully read all the lines and write it in the file.but when it writes in the file, it write the value in between " "(double quotes) like as("abcdefgh3 12345678")what i want actually to remove this "" double quotes sign when i write it in to the files.i am pasting my code here:
static void Main(string[] args)
{
var reader = new StreamReader(File.OpenRead(#"C:\Desktop\userid1.csv"));
List<string> listA = new List<string>();
while (!reader.EndOfStream)
{
var line = reader.ReadLine();
var values = line.Split(',');
listA.Add(values[0]);
listA.Add(values[1]);
}
foreach (string a in listA)
{
TextWriter tr = new StreamWriter(#"E:\newfiless",true);
tr.Write(a);
tr.Write(tr.NewLine);
tr.Close();
}
}
and the resulted output is like this:
"uid
pass"
"Martin123
123456789"
"Damian
91644"
but i want in this form:
uid
pass
Martin123
123456789
Damian
91644
Thanking you all in advance.
The original file clearly has quotes, which makes it a CSV file with only one colum and in that column there are two values. Not usual, but it happens.
To actually remove quotes you can use Trim, TrimEnd or TrimStart.
You can remove the quotes while reading, or while writing, in this case it doesn't really matter.
var line = reader.ReadLine().Trim('"');
This will remove the quotes while reading. Note that this assumes the CSV is of this "broken" variant.
tr.WriteLine(a.Trim('"'));
This will handle it on write. This will work even if the file is "correct" CSV having two columns and values in quotes.
Note that you can use WriteLine to add the newline, no need for two Write calls.
Also as others have commented, don't create a TextWriter in the loop for every value, create it once.
using (TextWriter tr = new StreamWriter(#"E:\newfiless"))
{
foreach (string a in listA)
{
tr.WriteLine(a.Trim('"'));
}
}
The using will take care of closing the file and other possible resources even if there is an exception.
I assume that all you need to read the input file, strip out all starting/ending quotation marks, then split by comma and write it all to another file. You can actually accomplish it in a one-liner using SelectMany, which will produce a "flat" collection:
File.WriteAllLines(
#"c:\temp\output.txt",
File
.ReadAllLines(#"c:\temp\input.csv")
.SelectMany(line => line.Trim('"').Split(','))
);
It's not quite clear from your example where quotation marks are located in the file. For a typical .CSV file some comma-separated field might be wrapped in quotation marks to allow commas to be a part of the content. If it's the case, then parsing will be more complex.
You can use
tr.Write(a.Substring(1, line.Length - 2));
Edited
Please use Trim
tr.Write(a.TrimEnd('"').TrimStart('"'));
so I have this application that I have inherited from someone that is long gone. The gist of the application is that it reads in a .cvs file that has about 5800 lines in it, copies it over to another .cvs, which it creates new each time, after striping out a few things , #, ', &. Well everything works great, or it has until about a month ago. so I started checking into it, and what I have found so far is that there are about 131 items missing from the spreadsheet. Now I read someplace that the maximun amount of data a string can hold is over 1,000,000,000 chars, and my spreadsheet is way under that, around 800,000 chars, but the only thing I can think is doing it is the string object.
So anyway, here is the code in question, this piece appears
to both read in from the existing field, and output to the new file:
StreamReader s = new StreamReader(File);
//Read the rest of the data in the file.
string AllData = s.ReadToEnd();
//Split off each row at the Carriage Return/Line Feed
//Default line ending in most windows exports.
//You may have to edit this to match your particular file.
//This will work for Excel, Access, etc. default exports.
string[] rows = AllData.Split("\r\n".ToCharArray(), System.StringSplitOptions.RemoveEmptyEntries);
//Now add each row to the DataSet
foreach (string r in rows)
{
//Split the row at the delimiter.
string[] items = r.Split(delimiter.ToCharArray());
//Add the item
result.Rows.Add(items);
}
If anyone can help me I would really appreciate it. I either need to figure out how to split the data better, or I need to figure out why it is cutting out the last 131 lines from the existing excel file to the new excel file.
One easier way to do this, since you're using "\r\n" for lines, would be to just use the built-in line reading method: File.ReadLines(path)
foreach(var line in File.ReadLines(path))
{
var items = line.Split(',');
result.Rows.Add(items);
}
You may want to check out the TextFieldParser class, which is part of the Microsoft.VisualBasic.FileIO namespace (yes, you can use this with C# code)
Something along the lines of:
using(var reader = new TextFieldParser("c:\\path\\to\\file"))
{
//configure for a delimited file
reader.TextFieldType = FieldType.Delimited;
//configure the delimiter character (comma)
reader.Delimiters = new[] { "," };
while(!reader.EndOfData)
{
string[] row = reader.ReadFields();
//do stuff
}
}
This class can help with some of the issues of splitting a line into its fields, when the field may contain the delimiter.
I used MyString.Split(Environment.Newline.ToCharArray()[0]) to split my string from a file into different pieces. But, every item in the array, except the first one starts with \n after I did that? I know the way that I'm splitting by newlines is kind of "cheaty" for lack of a better word, so if there is a better way of doing this, please tell me...
Here is the file...
If you are wanting to maintain using the .Split() instead of reading a file in a line at a time you can do...
var splitResult = MyString.Split( new string[]{ System.Environment.NewLine },
System.StringSplitOptions.RemoveEmptyEntries );
/* or System.StringSplitOptions.None if you want empty results as well */
EDIT:
The problem you were having is that in a non-unix environment the new-line "character" is actually two characters. So when you grabbed the zero index you were actually splitting on a carriage return...not the new-line character (\n).
Windows = "\r\n"
Unix = "\n"
Per http://msdn.microsoft.com/en-us/library/system.environment.newline.aspx
A newline in Windows is two characters (\r and \n). The Environment.Newline.ToCharArray()[0] expression specifies only one of those characters: \r. Therefore, the other character (\n) remains as a portion of the split string.
My I suggest you read your file using something like this:
public IEnumerable<string> ReadFile(string filePath)
{
using (StreamReader rdr = new StreamReader(filePath))
{
string line;
while ( (line = reader.ReadLine()) != null)
{
yield return line;
}
}
}
You might need more error handling, or to specify different file open option, or to pass a stream to method rather than the path, but the idea of using an iterator over the ReadLine() method is sound. The result is you can just use code like this:
foreach (string line in ReadLine(" ... my file path ... "))
{
}
I have an Excel spreadsheet being converted into a CSV file in C#, but am having a problem dealing with line breaks. For instance:
"John","23","555-5555"
"Peter","24","555-5
555"
"Mary,"21","555-5555"
When I read the CSV file, if the record does not starts with a double quote (") then a line break is there by mistake and I have to remove it. I have some CSV reader classes from the internet but I am concerned that they will fail on the line breaks.
How should I handle these line breaks?
Thanks everybody very much for your help.
Here's is what I've done so far. My records have fixed format and all start with
JTW;...;....;...;
JTW;...;...;....
JTW;....;...;..
..;...;... (wrong record, line break inserted)
JTW;...;...
So I checked for the ; in the [3] position of each line. If true, I write; if false, I'll append on the last (removing the line-break)
I'm having problems now because I'm saving the file as a txt.
By the way, I am converting the Excel spreadsheet to csv by saving as csv in Excel. But I'm not sure if the client is doing that.
So the file as a TXT is perfect. I've checked the records and totals. But now I have to convert it back to csv, and I would really like to do it in the program. Does anybody know how?
Here is my code:
namespace EditorCSV
{
class Program
{
static void Main(string[] args)
{
ReadFromFile("c:\\source.csv");
}
static void ReadFromFile(string filename)
{
StreamReader SR;
StreamWriter SW;
SW = File.CreateText("c:\\target.csv");
string S;
char C='a';
int i=0;
SR=File.OpenText(filename);
S=SR.ReadLine();
SW.Write(S);
S = SR.ReadLine();
while(S!=null)
{
try { C = S[3]; }
catch (IndexOutOfRangeException exception){
bool t = false;
while (t == false)
{
t = true;
S = SR.ReadLine();
try { C = S[3]; }
catch (IndexOutOfRangeException ex) { S = SR.ReadLine(); t = false; }
}
}
if( C.Equals(';'))
{
SW.Write("\r\n" + S);
i = i + 1;
}
else
{
SW.Write(S);
}
S=SR.ReadLine();
}
SR.Close();
SW.Close();
Console.WriteLine("Records Processed: " + i.ToString() + " .");
Console.WriteLine("File Created SucacessFully");
Console.ReadKey();
}
}
}
CSV has predefined ways of handling that. This site provides an easy to read explanation of the standard way to handle all the caveats of CSV.
Nevertheless, there is really no reason to not use a solid, open source library for reading and writing CSV files to avoid making non-standard mistakes. LINQtoCSV is my favorite library for this. It supports reading and writing in a clean and simple way.
Alternatively, this SO question on CSV libraries will give you the list of the most popular choices.
Rather than check if the current line is missing the (") as the first character, check instead to see if the last character is a ("). If it is not, you know you have a line break, and you can read the next line and merge it together.
I am assuming your example data was accurate - fields were wrapped in quotes. If quotes might not delimit a text field (or new-lines are somehow found in non-text data), then all bets are off!
There is a built-in method for reading CSV files in .NET (requires Microsoft.VisualBasic assembly reference added):
public static IEnumerable<string[]> ReadSV(TextReader reader, params string[] separators)
{
var parser = new Microsoft.VisualBasic.FileIO.TextFieldParser(reader);
parser.SetDelimiters(separators);
while (!parser.EndOfData)
yield return parser.ReadFields();
}
If you're dealing with really large files this CSV reader claims to be the fastest one you'll find: http://www.codeproject.com/Articles/9258/A-Fast-CSV-Reader
I've used this piece of code recently to parse rows from a CSV file (this is a simplified version):
private void Parse(TextReader reader)
{
var row = new List<string>();
var isStringBlock = false;
var sb = new StringBuilder();
long charIndex = 0;
int currentLineCount = 0;
while (reader.Peek() != -1)
{
charIndex++;
char c = (char)reader.Read();
if (c == '"')
isStringBlock = !isStringBlock;
if (c == separator && !isStringBlock) //end of word
{
row.Add(sb.ToString().Trim()); //add word
sb.Length = 0;
}
else if (c == '\n' && !isStringBlock) //end of line
{
row.Add(sb.ToString().Trim()); //add last word in line
sb.Length = 0;
//DO SOMETHING WITH row HERE!
currentLineCount++;
row = new List<string>();
}
else
{
if (c != '"' && c != '\r') sb.Append(c == '\n' ? ' ' : c);
}
}
row.Add(sb.ToString().Trim()); //add last word
//DO SOMETHING WITH LAST row HERE!
}
Try CsvHelper (a library I maintain). It ignores empty rows. I believe there is a flag you can set in FastCsvReader to have it handle empty rows also.
Heed the advice from the experts and Don't roll your own CSV parser.
Your first thought is, "How do I handle new line breaks?"
Your next thought is, "I need to handle commas inside of quotes."
Your next thought will be, "Oh, crap, I need to handle quotes inside of quotes. Escaped quotes. Double quotes. Single quotes..."
It's a road to madness. Don't write your own. Find a library with an extensive unit test coverage that hits all the hard parts and has gone through hell for you. For .NET, use the free CsvHelper library.
Maybe you could count for (") during the ReadLine(). If they are odd, that will raise the flag. You could either ignore those lines, or get the next two and eliminate the first "\n" occurrence of the merge lines.
What I usually do is read the text in character by character opposed to line by line, due to this very problem.
As you're reading each character, you should be able to figure out where each cell starts and stops, but also the difference between a linebreak in a row and in a cell: If I remember correctly, for Excel generated files anyway, rows start with \r\n, and newlines in cells are only \r.
There is an example parser is c# that seems to handle your case correctly. Then you can read your data in and purge the line breaks out of it post-read.
Part 2 is the parser, and there is a Part 1 that covers the writer portion.
Read the line.
Split into columns(fields).
If you have enough columns expected for each line, then process.
If not, read the next line, and capture the remaining columns until you get what you need.
Repeat.
A somewhat simple regular expression could be used on each line. When it matches, you process each field from the match. When it doesn't find a match, you skip that line.
The regular expression could look something like this.
Match match = Regex.Match(line, #"^(?:,?(?<q>['"](?<field>.*?\k'q')|(?<field>[^,]*))+$");
if (match.Success)
{
foreach (var capture in match.Groups["field"].Captures)
{
string fieldValue = capture.Value;
// Use the value.
}
}
Have a look at FileHelpers Library
It supports reading\writing CSV with line breaks as well as reading\writing to excel
The LINQy solution:
string csvText = File.ReadAllText("C:\\Test.txt");
var query = csvText
.Replace(Environment.NewLine, string.Empty)
.Replace("\"\"", "\",\"").Split(',')
.Select((i, n) => new { i, n }).GroupBy(a => a.n / 3);
You might also check out my CSV parser SoftCircuits.CsvParser on NuGet. It will not only parse a CSV file but--if wanted--can also automatically map column values to your class properties. And it runs nearly four times faster than CsvHelper.
For a line break to exist in a CSV, there must be an open double quote that's not closed.
Assuming that all CSVs cells must open and close a double quote, just check if there's an odd number of quotation marks
my_string.Count(c => c == '"') % 2 == 1
and if that's the case, continue reading until you have the even number.