Get file size given file descriptor in Go
Clash Royale CLAN TAG#URR8PPPGet file size given file descriptor in Go
If given a path, I would use this to get file size
file, _ := os.Open(path)
fi, _ := file.Stat()
fsuze := fi.Size()
But if only given fd, how can I get the file size?
Is there any way in golang like
fd
lseek(fd, 0, SEEK_END)
in C
Can I get File stat without opening the file?
Just like C, given path
int stat(const char*path, struct stat *statbuf)
I just looked into the golang os package and found
func Stat(name string) (FileInfo, error)
just like C's
int stat(const char*path, struct stat *statbuf)
fd
open()
Yes. I get this fd by calling os.File.stat().Fd()
– Cubey Mew
27 mins ago
2 Answers
2
You create a new *os.File from a file descriptor using the os.NewFile function.
*os.File
os.NewFile
You can do it exactly the same way as in C, using Seek
Seek
offset, err := f.Seek(0, os.SEEK_END)
But since you have the *os.File already, you can call Stat even if it was derived directly from the file descriptor.
*os.File
Stat
What will happen if I call os.NewFile, with the current file open. Does the new file a copy of the current file?
– Cubey Mew
20 mins ago
@CubeyMew: It's the same file descriptor, so nothing happens. Even if you opened it with a new fd, opening a file does not copy it.
– JimB
17 mins ago
I want to use Open first to get a *File. And later use Create(name string)(*File, error) to get the *os.File. Will this cause any effect on the file? (I dont want to pass *os.File as parameter or make it as struct member)
– Cubey Mew
12 mins ago
@CubeyMew: opening a file has doesn't effect the file. If the file doesn't exist, the obviously
os.Create will have an effect.– JimB
6 mins ago
os.Create
ok. Thanks for your answer
– Cubey Mew
5 mins ago
try to get the file start
fileInfo, err := file.Stat()
if err != nil {...
}
files fileInfo.Size())
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Just to clarify, does
fdmean an integer file descriptor, as one would get fromopen()in C?– Jonathon Reinhart
41 mins ago