C++ problem with files

[tkjacobsen]

I'm making a small c++ linux program.
How do I check if a file exists (a configuration file)
How do I detect the home folder of the user running the program
How do I create a folder in $HOME

I need the program to check if the configuretion file exists, and if not, create a folder in $HOME and in that folder create the configuration file..

[khedron]

Ok, to see if a file exists, try opening it for reading. The opening will fail if there is no file.

To get $HOME, include <cstdlib> and use the getenv function. More details here:
http://www.acm.uiuc.edu/webmonkeys/book/c_guide/2.13.html#getenv

Getenv takes a char* (a c-string) as an argument and returns one as well. I haven't used it (yet), you'll have to experiment.

To make a folder, look at this question: http://c-faq.com/osdep/mkdir.html
It's about C, unfortunately, not C++, but my experience so far has been with C. I'm only now learning C++.

[hod139]

Check out the Boost Filesystem Library as well. (http://www.boost.org/libs/filesystem/doc/index.htm) The Boost solution will be more complicated, but portable.

[tkjacobsen]

Thanks guys. I will try all options out as soon as possible and write back how it went afterwards.

[xtacocorex]

Here is some simple stuff I've done to find a config file with an environment variable:


#include<iostream>
#include<string>
#include<fstream>
#include<stdlib.h>

// config
// ===============================================
// Reads in the configuration parameters for PMARC
void config()
{
// Variable declarations
std::string t1, t2, cfignlist, fpath;
char *path;
std::ifstream fin;

// Get the path to the PMARC config file
path = getenv("PMARCCONFIG");
// If path doesn't exits, throw out error and exit program
if (path == NULL)
{
std::cout << "ERROR-UNABLE TO FIND ENVIRONMENT VARIABLE: PMARCCONFIG" << std::endl;
std::exit(1);
}

// Set string that holds the path and filename of the config file
// This resize needs stay
fpath.resize(strlen(path)+11);
for (int i=0;i<=strlen(path);i++)
{
fpath[i]=path[i];
}
fpath += "/pmarc.conf";

// *** FOR TESTING ***
fpath="pmarc.conf";

// Open the file
fin.open(fpath.c_str());
// If it fails, show error and exit
if (fin.fail() == true)
{
std::cout << "ERROR-PMARC CONFIGURATION FILE CANNOT BE OPENED" << std::endl;
std::exit(1);
}
// Otherwise do the work to parse the namelist
else
{
// Get the lines from the input file
std::getline(fin,t1);
std::getline(fin,t2);

// Close the file
fin.close();
}
// Return to calling routine
} // End config


Hope this helps some.

[g8m]

If you're configuration file is in ini-like format.
Like:
[header1]
variable1 = value1
variable2 = value2

[header2]
variable3 = value3

You might want to have a look at key-value file parser functions from glib top parse ini-files
http://developer.gnome.org/doc/API/2.0/glib/glib-Key-value-file-parser.html

[RealTonko]

You may want to delegate those issues to config and make install.
Check http://sourceware.org/autobook/