I need to implement simple function to get current directory from
program directory.

e.g. /home/tatu/src/main -> /home/tatu/src
where main is the currently running program.
i.e. argv[0] == /home/tatu/src/main.

First, I did it with C-style:

// start-of-file

static const char*
parse_currentdir(const char* const program_location)
{
  register int i;
  const char* const loc = program_location;

  size_t size = strlen(loc);

  for (i = (size - 1);  (i >= 0) && (loc[i] != DIR_SEPARATOR); --i)
    ;

  if (loc[i] == DIR_SEPARATOR)
  {
    char* curdir = (char*) malloc((i + 1) * sizeof(char));
    if (curdir != NULL)
    {
      strncpy (curdir, loc, (size_t) i);
      curdir[i] = '\0';
      return curdir;
    }
    else
    {
      // Memory allocation error.
    }
  }
  else
  {
    // There was no DIR_SEPARATOR in LOC.
  }

  const char* curdir = ".";
  return curdir;
}

int
main (int argc, const char* const argv[])
{
  const char* curdir = parse_currentdir (argv[0]);
  return 0;
}

// end-of-file

But then I don't learn anything about C++. In particular, I found
out[1] that I could use find_last_of() member routine of C++ string
class. But find_last_of() returns type of size_type, and I cannot
figure out how I should use the size_type to create smaller string
containing only current path.

Can I convert size_type to an iterator?


[1] found out:
http://www.cppreference.com/cppstring/end.html
If you know better reference pages, please include them in your
answer.

"Tatu Portin" <axel86@mbnet.fi> wrote in message 
news:nGohf.338$nf2.102@read3.inet.fi...
>I need to implement simple function to get current directory from
> program directory.
>
> e.g. /home/tatu/src/main -> /home/tatu/src
> where main is the currently running program.
> i.e. argv[0] == /home/tatu/src/main.
>
> First, I did it with C-style:
>
> // start-of-file
>
> static const char*
> parse_currentdir(const char* const program_location)
> {
>  register int i;
>  const char* const loc = program_location;
>
>  size_t size = strlen(loc);
>
>  for (i = (size - 1);  (i >= 0) && (loc[i] != DIR_SEPARATOR); --i)
>    ;
>
>  if (loc[i] == DIR_SEPARATOR)
>  {
>    char* curdir = (char*) malloc((i + 1) * sizeof(char));
>    if (curdir != NULL)
>    {
>      strncpy (curdir, loc, (size_t) i);
>      curdir[i] = '\0';
>      return curdir;
>    }
>    else
>    {
>      // Memory allocation error.
>    }
>  }
>  else
>  {
>    // There was no DIR_SEPARATOR in LOC.
>  }
>
>  const char* curdir = ".";
>  return curdir;
> }
>
> int
> main (int argc, const char* const argv[])
> {
>  const char* curdir = parse_currentdir (argv[0]);
>  return 0;
> }
>
> // end-of-file
>
> But then I don't learn anything about C++. In particular, I found
> out[1] that I could use find_last_of() member routine of C++ string
> class. But find_last_of() returns type of size_type, and I cannot
> figure out how I should use the size_type to create smaller string
> containing only current path.
>
> Can I convert size_type to an iterator?

For sequences which support random-access iterators
(of which string is one):

iterator + size_type == iterator
iterator - size_type == iterator
iterator - iterator  == size type
iterators begin() and/or end() could be useful in computations

All this is subject to boundary rules of course.


-Mike

Mike Wahler wrote:

> 
> "Tatu Portin" <axel86@mbnet.fi> wrote in message
> news:nGohf.338$nf2.102@read3.inet.fi...
>>I need to implement simple function to get current directory from
>> program directory.
>>
>> e.g. /home/tatu/src/main -> /home/tatu/src
>> where main is the currently running program.
>> i.e. argv[0] == /home/tatu/src/main.
>>
>> First, I did it with C-style:
>>
>> // start-of-file
>>
>> static const char*
>> parse_currentdir(const char* const program_location)
>> {
>>  register int i;
>>  const char* const loc = program_location;
>>
>>  size_t size = strlen(loc);
>>
>>  for (i = (size - 1);  (i >= 0) && (loc[i] != DIR_SEPARATOR); --i)
>>    ;
>>
>>  if (loc[i] == DIR_SEPARATOR)
>>  {
>>    char* curdir = (char*) malloc((i + 1) * sizeof(char));
>>    if (curdir != NULL)
>>    {
>>      strncpy (curdir, loc, (size_t) i);
>>      curdir[i] = '\0';
>>      return curdir;
>>    }
>>    else
>>    {
>>      // Memory allocation error.
>>    }
>>  }
>>  else
>>  {
>>    // There was no DIR_SEPARATOR in LOC.
>>  }
>>
>>  const char* curdir = ".";
>>  return curdir;
>> }
>>
>> int
>> main (int argc, const char* const argv[])
>> {
>>  const char* curdir = parse_currentdir (argv[0]);
>>  return 0;
>> }
>>
>> // end-of-file
>>
>> But then I don't learn anything about C++. In particular, I found
>> out[1] that I could use find_last_of() member routine of C++ string
>> class. But find_last_of() returns type of size_type, and I cannot
>> figure out how I should use the size_type to create smaller string
>> containing only current path.
>>
>> Can I convert size_type to an iterator?
> 
> For sequences which support random-access iterators
> (of which string is one):
> 
> iterator + size_type == iterator
> iterator - size_type == iterator
> iterator - iterator  == size type
> iterators begin() and/or end() could be useful in computations
> 
> All this is subject to boundary rules of course.

Thanks. Got it working the C++ way.