ofstream problem

[Ron Eggler]

Hi,

I'm trying to write to a text file with following code:
std::ofstream out("/usr/share/NovaxTSP/INITreport.txt" , std::ios_base:: in |
std::ios_base:: out | std::ios_base:: app);
if(!out) { // if out couldn't be opened, print error and exit
std::cout << "Cannot open reportfile:
\"/usr/share/NovaxTSP/INITreport.txt\ "." << std::endl;
exit(0);
}
double num = 100.45;
char str[100];
strcpy(str, newLine.c_str() );
strcat(str,"\n\ r");
out.write((char *) &num, sizeof(double)) ;
out.write(str, strlen(str));
out.close();

the folder /usr/share/NovaxTSP/ has permissions set to 775 and the
application is run as root but i still always get: Cannot open
reportfile: "/usr/share/NovaxTSP/INITreport.txt" .
Why??? I don't understand, i made a df -h and there's enough space available
as well.
Does anyone have any other ideas on what to check?
I also touched the file before appending but that didn't change it either.

I appreciate every input!

Thank you to help me further!

Ron

[Gianni Mariani]

Re: ofstream problem

Ron Eggler wrote:

Hi,
>
I'm trying to write to a text file with following code:
std::ofstream out("/usr/share/NovaxTSP/INITreport.txt" , std::ios_base:: in |
std::ios_base:: out | std::ios_base:: app);
if(!out) { // if out couldn't be opened, print error and exit
std::cout << "Cannot open reportfile:
\"/usr/share/NovaxTSP/INITreport.txt\ "." << std::endl;
exit(0);
}
double num = 100.45;
char str[100];

NEVER EVER EVER DECLARE A CHAR ARRAY ON STACK

strcpy(str, newLine.c_str() );

AND THEN FILL IT WITH AN UNBOUND STRING.

strcat(str,"\n\ r");

"\n\r" is operating system specific. If you write that to some
platforms (MSVC) for example, you'll get more than one \r.

What's wrong with:
std::string str = newLine + "\n";
?

That code above will work correctly for any "newLine".

out.write((char *) &num, sizeof(double)) ;

This is also endian dependant - not good depending on your use for the
output file. Are you really trying to write the bitwise representation
of the machine specific "double" type ?

out.write(str, strlen(str));
out.close();
>
the folder /usr/share/NovaxTSP/ has permissions set to 775 and the
application is run as root but i still always get: Cannot open
reportfile: "/usr/share/NovaxTSP/INITreport.txt" .

If you're running under linux, try

touch /usr/share/NovaxTSP/INITreport.txt

Or run your program under strace and see what error you're getting back
from the OS.