Argv

[broeks]

I'm trying to create an array of character arrays. I would use strings,
but the function I need to feed into looks like this

int execve(const char *filename, char *const argv [], char *const
envp[] ). I know this is not a C++ function, and I only ask for how to
create something that a function like this will actually accept.

I will not know the amount of character arrays (arguments) until
runtime, so I need to use new or calloc to get this done.

I've successfully parsed all the arguments into strings, and placed
them in a nice vector. (Probably an unnecessary step, but hey)

so something like

make charray;
for(int i =0; i< vector.size(); i++){

chararray[i][vector[i].c_str()];

}

return something that will pass into the above function.

Sorry if this seems weird.

Thanks for Reading.

A tired java person.

[Heinz Ozwirk]

<br****@gmail.c om> schrieb im Newsbeitrag news:11******** **************@ g10g2000cwb.goo glegroups.com.. .

I'm trying to create an array of character arrays. I would use strings,
but the function I need to feed into looks like this

int execve(const char *filename, char *const argv [], char *const
envp[] ). I know this is not a C++ function, and I only ask for how to
create something that a function like this will actually accept.

The function expects two arrays of pointers to char, not "arrays of character arrays". Something like

char** argv = new char*[numberOfStrings + 1];
for (int i = 0; i < numberOfStrings ; ++i)
argv[i] = somePointerToNo nConstCharacter (s);
argv[numberOfStrings] = 0;

should help.

Heinz

[akiross]

i think this can work:

char **array;
array = malloc(sizeof(c har *) * NUMBER_OF_STRIN GS);
-------or-------
char *array[MAX_NUMBER_OF_S TRINGS]; (if you don't like a malloc here :)

then:
int i;
char buffer[1024];
fgets(char *s, int size, FILE *stream);
for (i = 0; i < NUMBER_OF_STRIN GS; i++)
{
fgets(buffer, 1024, stdin); // get the ith string
array[i] = malloc(sizeof(b uffer)); // create new string in the
array
strcpy(array[i], buffer); // assign the string
}

execve(blah, array, blah); // pass the array

does it work?

[akiross]

Ops sorry, i forgot this was the c.l.c++, i replied in C :] Sorry!

[??]

perhalps need a argc to count the size
<br****@gmail.c om>
??????:11****** *************** *@g10g2000cwb.g ooglegroups.com ...

I'm trying to create an array of character arrays. I would use strings,
but the function I need to feed into looks like this

int execve(const char *filename, char *const argv [], char *const
envp[] ). I know this is not a C++ function, and I only ask for how to
create something that a function like this will actually accept.

I will not know the amount of character arrays (arguments) until
runtime, so I need to use new or calloc to get this done.

I've successfully parsed all the arguments into strings, and placed
them in a nice vector. (Probably an unnecessary step, but hey)

so something like

make charray;
for(int i =0; i< vector.size(); i++){

chararray[i][vector[i].c_str()];

}

return something that will pass into the above function.

Sorry if this seems weird.

Thanks for Reading.

A tired java person.

[pillbug]

>

I've successfully parsed all the arguments into strings, and placed
them in a nice vector. (Probably an unnecessary step, but hey)

char** vector_to_valis t (const std::vector<std ::string>& vect)
{
std::auto_ptr<c har*> valist (new char* [vect.size()]);
std::transform (vect.begin(), vect.end(),
const_cast<cons t char**> (valist.get()),
std::mem_fun_re f (&std::string:: c_str));
return valist.release( );
}

theres some const breakage going on here, but the exec family doesn't
mod the strings anyway.

[Daniel T.]

In article <11************ **********@g10g 2000cwb.googleg roups.com>,
br****@gmail.co m wrote:

I'm trying to create an array of character arrays. I would use strings,
but the function I need to feed into looks like this

int execve(const char *filename, char *const argv [], char *const
envp[] ). I know this is not a C++ function, and I only ask for how to
create something that a function like this will actually accept.
From unistd.h right?
I will not know the amount of character arrays (arguments) until
runtime, so I need to use new or calloc to get this done.
No, don't use calloc. Don't ever use calloc in a C++ program.
I've successfully parsed all the arguments into strings, and placed
them in a nice vector. (Probably an unnecessary step, but hey)

so something like

make charray;
for(int i =0; i< vector.size(); i++){

chararray[i][vector[i].c_str()];
The problem with that is that both argv and envp must contain modifiable
strings (char* not const char*.)
return something that will pass into the above function.

Sorry if this seems weird.

struct extract_buffer : unary_function< char*, vector<char> > {
char* operator()( vector<char>& vec ) const {
return &vec[0];
}
};

typedef vector< vector< char > > RaggedArray;

int execve( const char* filename, RaggedArray& argv,
RaggedArray& envp ) {
vector<char*> argv_guts;
transform( argv.begin(), argv.end(), back_inserter( argv_guts ),
extract_buffer( ) );
vector<char*> envp_guts;
transform( envp.begin(), envp.end(), back_inserter( envp_guts ),
extract_buffer( ) );
return execve( filename, &argv_guts[0], &envp_guts[0] );
}
--
Magic depends on tradition and belief. It does not welcome observation,
nor does it profit by experiment. On the other hand, science is based
on experience; it is open to correction by observation and experiment.

[Phlip]

pillbug wrote:

I've successfully parsed all the arguments into strings, and placed
them in a nice vector. (Probably an unnecessary step, but hey)
char** vector_to_valis t (const std::vector<std ::string>& vect)
{
std::auto_ptr<c har*> valist (new char* [vect.size()]);

auto_ptr should not control an array returned by new[], because the result
of calling delete (without []) on it is undefined.
std::transform (vect.begin(), vect.end(),
const_cast<cons t char**> (valist.get()),
std::mem_fun_re f (&std::string:: c_str));
return valist.release( );
}

theres some const breakage going on here, but the exec family doesn't
mod the strings anyway.

I don't trust that const_cast. Why not use vector<char*> valist, then get
its first element's address with &valist[0]?

--
Phlip
http://www.greencheese.org/ZeekLand <-- NOT a blog!!!

[Phlip]

pillbug wrote:

char** vector_to_valis t (const std::vector<std ::string>& vect)
{ .... return valist.release( );
}

I forgot to notice; that return value is just wrong. If you need a
vector<char*>, then return one. Or better vector<string>. Return it by
copy.

--
Phlip
http://www.greencheese.org/ZeekLand <-- NOT a blog!!!

[Diego Martins]

Daniel T. wrote:

I will not know the amount of character arrays (arguments) until
runtime, so I need to use new or calloc to get this done.

No, don't use calloc. Don't ever use calloc in a C++ program.

why? :-)
std::calloc() is quite useful in some cases