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Constructor
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 Posted: Thu Aug 28, 2003 3:09 pm Post subject: How to insert datas into a fstrem data |
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Hi all,
I just want to insert datas into a file, and i use fstream to open file,
but the openmode I use does'not works well, just like this
#include <fstream>
#include <iostream>
main( )
{
using namespace std;
fstream x( "iotest.txt", ios_base::out | ios_base::ate );
x.seekp(2,ios::beg) ;
x << "testing";
}
//iotest.txt has some data, like this:
//"this is a test"
//i just want to insert "testing" into the file, not append it to the end of
the file
also I test with the openmode "ios_base::app", but didn't get what i need.
of course, i can resolve it with fopen in c-style well, but i just want to
do it
in c++ style.
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Ulrich Eckhardt
Guest
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| Posted: Fri Aug 29, 2003 11:26 am Post subject: Re: How to insert datas into a fstrem data |
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Constructor wrote:
| Quote: | I just want to insert datas into a file, and i use fstream to open file,
but the openmode I use does'not works well, just like this
|
Just FYI: 'data' is the plural of datum.
| Quote: | #include <fstream
#include
|
You also need
most compilers though.
| Quote: | main( )
{
using namespace std;
fstream x( "iotest.txt", ios_base::out | ios_base::ate );
|
Alternatively use ofstream, you can then drop the 'ios_base::out'. Also
missing here:
if(!x)
{
cerr << "main(): failed to open file for writingn";
return -1;
}
| Quote: | x.seekp(2,ios::beg) ;
x << "testing";
}
//iotest.txt has some data, like this:
//"this is a test"
//i just want to insert "testing" into the file, not append it to the end
of the file
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Inserting will truncate the file. Inserting like in an editor is not
possible like that. Also I wonder
1. what happens, i.e. what are the results afterwards ?
2. what did you expect to be the file's content in the end ?
3. what happens if you remove the seekp() or the ios_base::ate ?
4 which compiler/stdlib do you use ? (there are still broken
implementations out there)
cheers
Uli
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