Determine the number of lines within a text file

Question

Is there an easy way to programmatically determine the number of lines within a text file

User · Answer

The easiest   int lines   File ReadAllLines  myfile   Length

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try       string path   args 0       FileStream fh   new FileStream path  FileMode Open  FileAccess Read       int i      string s           while   i   fh ReadByte       -1          s   s    char i         its for reading number of paragraphs     int count   0      for  int j   0  j  lt  s Length - 1  j                  if  s Substring j  1       n                   count               Console WriteLine  The total searches were      count        fh Close       catch Exception ex        Console WriteLine ex Message

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If by easy you mean a lines of code that are easy to decipher but per chance inefficient   string   lines   System IO File RealAllLines  filename   int cnt   lines Count      That s probably the quickest way to know how many lines    You could also do  depending on if you are buffering it in    for large files while     reads into buffer   string   lines   Regex Split buffer System Enviorment NewLine       There are other numerous ways but one of the above is probably what you ll go with

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Use this      int get lines string file                var lineCount   0          using  var stream   new StreamReader file                         while  stream ReadLine      null                                lineCount                                    return lineCount

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You can launch the  wc exe  executable  comes with UnixUtils and does not need installation  run as an external process  It supports different line count methods  like unix vs mac vs windows

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Reading a file in and by itself takes some time  garbage collecting the result is another problem as you read the whole file just to count the newline character s    At some point  someone is going to have to read the characters in the file  regardless if this the framework or if it is your code  This means you have to open the file and read it into memory if the file is large this is going to potentially be a problem as the memory needs to be garbage collected    Nima Ara made a nice analysis that you might take into consideration  Here is the solution proposed  as it reads 4 characters at a time  counts the line feed character and re-uses the same memory address again for the next character comparison    private const char CR     r     private const char LF     n     private const char NULL    char 0   public static long CountLinesMaybe Stream stream          Ensure NotNull stream  nameof stream         var lineCount   0L       var byteBuffer   new byte 1024   1024       const int BytesAtTheTime   4      var detectedEOL   NULL      var currentChar   NULL       int bytesRead      while   bytesRead   stream Read byteBuffer  0  byteBuffer Length    gt  0                var i   0          for    i  lt   bytesRead - BytesAtTheTime  i    BytesAtTheTime                        currentChar    char byteBuffer i                if  detectedEOL    NULL                                if  currentChar    detectedEOL    lineCount                       currentChar    char byteBuffer i   1                   if  currentChar    detectedEOL    lineCount                       currentChar    char byteBuffer i   2                   if  currentChar    detectedEOL    lineCount                       currentChar    char byteBuffer i   3                   if  currentChar    detectedEOL    lineCount                                else                               if  currentChar    LF    currentChar    CR                                        detectedEOL   currentChar                      lineCount                                      i -  BytesAtTheTime - 1                                   for    i  lt  bytesRead  i                          currentChar    char byteBuffer i                if  detectedEOL    NULL                                if  currentChar    detectedEOL    lineCount                                else                               if  currentChar    LF    currentChar    CR                                        detectedEOL   currentChar                      lineCount                                                         if  currentChar    LF  amp  amp  currentChar    CR  amp  amp  currentChar    NULL                lineCount              return lineCount      Above you can see that a line is read one character at a time as well by the underlying framework as you need to read all characters to see the line feed        If you profile it as done bay Nima you would see that this is a rather fast and efficient way of doing this

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A viable option  and one that I have personally used  would be to add your own header to the first line of the file  I did this for a custom model format for my game  Basically  I have a tool that optimizes my  obj files  getting rid of the crap I don t need  converts them to a better layout  and then writes the total number of lines  faces  normals  vertices  and texture UVs on the very first line  That data is then used by various array buffers when the model is loaded    This is also useful because you only need to loop through the file once to load it in  instead of once to count the lines  and again to read the data into your created buffers

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You could quickly read it in  and increment a counter  just use a loop to increment  doing nothing with the text

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This would use less memory  but probably take longer  int count   0  string line  TextReader reader   new StreamReader  file txt    while   line   reader ReadLine       null      count      reader Close

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Seriously belated edit  If you re using  NET 4 0 or later  The File class has a new ReadLines method which lazily enumerates lines rather than greedily reading them all into an array like ReadAllLines  So now you can have both efficiency and conciseness with   var lineCount   File ReadLines   C  file txt   Count        Original Answer  If you re not too bothered about efficiency  you can simply write   var lineCount   File ReadAllLines   C  file txt   Length    For a more efficient method you could do   var lineCount   0  using  var reader   File OpenText   C  file txt          while  reader ReadLine      null                lineCount              Edit  In response to questions about efficiency  The reason I said the second was more efficient was regarding memory usage  not necessarily speed  The first one loads the entire contents of the file into an array which means it must allocate at least as much memory as the size of the file  The second merely loops one line at a time so it never has to allocate more than one line s worth of memory at a time  This isn t that important for small files  but for larger files it could be an issue  if you try and find the number of lines in a 4GB file on a 32-bit system  for example  where there simply isn t enough user-mode address space to allocate an array this large    In terms of speed I wouldn t expect there to be a lot in it  It s possible that ReadAllLines has some internal optimisations  but on the other hand it may have to allocate a massive chunk of memory  I d guess that ReadAllLines might be faster for small files  but significantly slower for large files  though the only way to tell would be to measure it with a Stopwatch or code profiler

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count the carriage returns line feeds  I believe in unicode they are still 0x000D and 0x000A respectively  that way you can be as efficient or as inefficient as you want  and decide if you have to deal with both characters or not

[c#] Determine the number of lines within a text file

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