I am using fs.Length
, where fs
is a FileStream
.
Is this an O(1)
operation? I would think this would just read from the properties of the file, as opposed to going through the file to find when the seek position has reached the end. The file I am trying to find the length of could easily range from 1 MB to 4-5 GB.
However I noticed that there is a FileInfo
class, which also has a Length
property.
Do both of these Length
properties theoretically take the same amount of time? Or does is fs.Length
slower because it must open the FileStream
first?
Using stat() function The stat() function takes the file path and returns a structure containing information about the file pointed by it. To get the size of the file in bytes, use the st_size field of the returned structure.
Locate the file or folder whose size you would like to view. Click the file or folder. Press Command + I on your keyboard. A window opens and shows the size of the file or folder.
FILE *fp; To open a file you need to use the fopen function, which returns a FILE pointer. Once you've opened a file, you can use the FILE pointer to let the compiler perform input and output functions on the file.
The datatype size_t is unsigned integral type. It represents the size of any object in bytes and returned by sizeof operator. It is used for array indexing and counting. It can never be negative. The return type of strcspn, strlen functions is size_t.
The natural way to get the file size in .NET is the FileInfo.Length property you mentioned.
I am not sure Stream.Length
is slower (it won't read the whole file anyway), but it's definitely more natural to use FileInfo
instead of a FileStream
if you do not plan to read the file.
Here's a small benchmark that will provide some numeric values:
private static void Main(string[] args) { string filePath = ...; // Path to 2.5 GB file here Stopwatch z1 = new Stopwatch(); Stopwatch z2 = new Stopwatch(); int count = 10000; z1.Start(); for (int i = 0; i < count; i++) { long length; using (Stream stream = new FileStream(filePath, FileMode.Open)) { length = stream.Length; } } z1.Stop(); z2.Start(); for (int i = 0; i < count; i++) { long length = new FileInfo(filePath).Length; } z2.Stop(); Console.WriteLine(string.Format("Stream: {0}", z1.ElapsedMilliseconds)); Console.WriteLine(string.Format("FileInfo: {0}", z2.ElapsedMilliseconds)); Console.ReadKey(); }
Results:
Stream: 886 FileInfo: 727
Both will access the file system metadata rather than reading the whole file. I don't know which is more efficient necessarily, as a rule of thumb I'd say that if you only want to know the length (and other metadata), use FileInfo
- whereas if you're opening the file as a stream anyway, use FileStream.Length
.
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