size of a file

[=?ISO-8859-1?Q?Andreas_M=FCller?=]

Is there a way to determine the size of a file before/without reading
all chars?

for example:

ifstream test("test.txt");
//i need the file size here

while(test.read(buffer,size));
....
//i can get it here but i need to know how often the loop will be executed.

 

[cadull]

I use:

test.seekg(0, std::ios::end);
size = test.tellg();
test.seekg(0);

but would prefer a better alternative should one exist.

Regards,
cadull

 

[John Carson]

Is there a way to determine the size of a file before/without reading
all chars?

for example:

ifstream test("test.txt");
//i need the file size here

while(test.read(buffer,size));
...
//i can get it here but i need to know how often the loop will be
executed.

Some files have headers giving this information, but of course a plain text
file doesn't.

The operating system you are using may provide an API to query file size,
e.g., there is GetFileSize on Windows.

The Boost filesystem library provides a file_size() function.

 

[=?ISO-8859-15?Q?Andreas_M=FCller?=]

I use:

test.seekg(0, std::ios::end);
size = test.tellg();
test.seekg(0);

I also tried this but shouldn't size contain the number of bytes?
I always get a confusing value, the filesize is 16,1KB but i always get
14416517 by printing out size. what's wrong?

 

[=?ISO-8859-1?Q?Andreas_M=FCller?=]

I also tried this but shouldn't size contain the number of bytes?
I always get a confusing value, the filesize is 16,1KB but i always get
14416517 by printing out size. what's wrong?

sorry my fault, i fixed it. thanks

 

[Chris \( Val \)]

| Is there a way to determine the size of a file before/without reading
| all chars?
|
| for example:
|
| ifstream test("test.txt");
| //i need the file size here
|
| while(test.read(buffer,size));
| ...
| //i can get it here but i need to know how often the loop will be executed.

Store it first, and note that it is opened in
binary mode to obtain an accurate positioning:

# include <iostream>
# include <fstream>
# include <ios>
# include <exception>

typedef std::ifstream:os_type pos_type;
pos_type get_file_size( const std::string& filename )
{
std::ifstream InFile( filename.c_str(),
std::ios_base::binary | std::ios_base::ate );

if( !InFile )
throw std::runtime_error( "ERROR: Could not obtain file size "
"for [" + filename + "]\n" );

return InFile.tellg();
}

int main()
{
pos_type pos = get_file_size( "X.txt" );

// ...

return 0;
}

Cheers,
Chris Val

 

[Larry I Smith]

Is there a way to determine the size of a file before/without reading
all chars?

for example:

ifstream test("test.txt");
//i need the file size here

while(test.read(buffer,size));
...
//i can get it here but i need to know how often the loop will be executed.

Many systems provide the stat() and fstat() functions
which return a struct of info on the file; the struct
includes the file's size.

Larry

 

[Alex Vinokur]

Is there a way to determine the size of a file before/without reading
all chars?

for example:

ifstream test("test.txt");
//i need the file size here

while(test.read(buffer,size));
...
//i can get it here but i need to know how often the loop will be executed.

Samples can be seen at
http://groups-beta.google.com/group/alt.sources/msg/41464ce8b75f8417