How to read an entire file to a string using C

Question

What is the quickest way to read a text file into a string variable   I understand it can be done in several ways  such as read individual bytes and then convert those to string  I was looking for a method with minimal coding

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System IO StreamReader myFile      new System IO StreamReader  c   test txt    string myString   myFile ReadToEnd

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you can use     public static void ReadFileToEnd         try             provide to reader your complete text file         using  StreamReader sr   new StreamReader  TestFile txt                          String line   sr ReadToEnd                Console WriteLine line                       catch  Exception e                Console WriteLine  The file could not be read             Console WriteLine e Message

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Take a look at the File ReadAllText   method  Some important remarks      This method opens a file  reads each line of the file  and then adds   each line as an element of a string  It then closes the file  A line   is defined as a sequence of characters followed by a carriage return      r    a line feed    n    or a carriage return immediately followed   by a line feed  The resulting string does not contain the terminating   carriage return and or line feed       This method attempts to automatically detect the encoding of a file   based on the presence of byte order marks  Encoding formats UTF-8 and   UTF-32  both big-endian and little-endian  can be detected       Use the ReadAllText String  Encoding  method overload when reading   files that might contain imported text  because unrecognized   characters may not be read correctly        The file handle is guaranteed to be closed by this method  even if   exceptions are raised

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For the noobs out there who find this stuff fun and interesting  the fastest way to read an entire file into a string in most cases  according to these benchmarks  is by the following   using  StreamReader sr   File OpenText fileName             string s   sr ReadToEnd        you then have to process the string   However  the absolute fastest to read a text file overall appears to be the following   using  StreamReader sr   File OpenText fileName             string s   String Empty          while   s   sr ReadLine       null                             do what you have to here               Put up against several other techniques  it won out most of the time  including against the BufferedReader

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You can use like this  public static string ReadFileAndFetchStringInSingleLine string file                StringBuilder sb          try                       sb   new StringBuilder                using  FileStream fs   File Open file  FileMode Open                                 using  BufferedStream bs   new BufferedStream fs                                         using  StreamReader sr   new StreamReader bs                                                 string str                          while   str   sr ReadLine       null                                                        sb Append str                                                                                               return sb ToString                      catch  Exception ex                        return                       Hope this will help you

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you can read a text from a text file in to string as follows also  string str       StreamReader sr   new StreamReader Application StartupPath      Sample txt    while sr Peek      -1      str   str   sr ReadLine

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Cris sorry  This is quote MSDN Microsoft   Methodology  In this experiment  two classes will be compared  The StreamReader and the FileStream class will be directed to read two files of 10K and 200K in their entirety from the application directory   StreamReader  VB NET   sr   New StreamReader strFileName  Do   line   sr ReadLine   Loop Until line Is Nothing sr Close    FileStream  VB NET   Dim fs As FileStream Dim temp As UTF8Encoding   New UTF8Encoding True  Dim b 1024  As Byte fs   File OpenRead strFileName  Do While fs Read b  0  b Length   gt  0     temp GetString b  0  b Length  Loop fs Close     Result    FileStream is obviously faster in this test  It takes an additional 50  more time for StreamReader to read the small file  For the large file  it took an additional 27  of the time   StreamReader is specifically looking for line breaks while FileStream does not  This will account for some of the extra time   Recommendations  Depending on what the application needs to do with a section of data  there may be additional parsing that will require additional processing time  Consider a scenario where a file has columns of data and the rows are CR LF delimited  The StreamReader would work down the line of text looking for the CR LF  and then the application would do additional parsing looking for a specific location of data   Did you think String  SubString comes without a price    On the other hand  the FileStream reads the data in chunks and a proactive developer could write a little more logic to use the stream to his benefit  If the needed data is in specific positions in the file  this is certainly the way to go as it keeps the memory usage down   FileStream is the better mechanism for speed but will take more logic

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string contents   System IO File ReadAllText path    Here s the MSDN documentation

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string text   File ReadAllText  Path    you have all text in one string variable  If you need each line individually you can use this   string   lines   File ReadAllLines  Path

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I made a comparison between a ReadAllText and StreamBuffer for a 2Mb csv and it seemed that the difference was quite small but ReadAllText seemed to take the upper hand from the times taken to complete functions

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How about File ReadAllText   string contents   File ReadAllText   C  temp test txt

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string content   System IO File ReadAllText    C  file txt

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well the quickest way meaning with the least possible C  code is probably this one   string readText   System IO File ReadAllText path

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if you want to pick file from Bin folder of the application then you can try following and don t forget to do exception handling   string content   File ReadAllText Path Combine System IO Directory GetCurrentDirectory      FilesFolder Sample txt

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A benchmark comparison of File ReadAllLines vs StreamReader ReadLine from C  file handling       Results  StreamReader is much faster for large files with 10 000    lines  but the difference for smaller files is negligible  As always    plan for varying sizes of files  and use File ReadAllLines only when   performance isn t critical      StreamReader approach  As the File ReadAllText approach has been suggested by others  you can also try the quicker  I have not tested quantitatively the performance impact  but it appears to be faster than File ReadAllText  see comparison below    The difference  in performance will be visible only in case of larger files though   string readContents  using  StreamReader streamReader   new StreamReader path  Encoding UTF8          readContents   streamReader ReadToEnd          Comparison of File Readxxx   vs StreamReader Readxxx    Viewing the indicative code through ILSpy I have found the following about File ReadAllLines  File ReadAllText    File ReadAllText  - Uses StreamReader ReadToEnd internally File ReadAllLines  - Also uses StreamReader ReadLine internally with the additionally overhead of creating the List lt string gt  to return as the read lines and looping till the end of file     So both the methods are an additional layer of convenience built on top of StreamReader  This is evident by the indicative body of the method    File ReadAllText   implementation as decompiled by ILSpy  public static string ReadAllText string path        if  path    null                throw new ArgumentNullException  path              if  path Length    0                throw new ArgumentException Environment GetResourceString  Argument EmptyPath               return File InternalReadAllText path  Encoding UTF8         private static string InternalReadAllText string path  Encoding encoding        string result      using  StreamReader streamReader   new StreamReader path  encoding                 result   streamReader ReadToEnd              return result

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