It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For help clarifying this question so that it can be reopened, visit the help center.
Closed 10 years ago.
I have to make a program where the filename is composed of two parts: the first one is fixed and the second one can change during the program e.g "fixpart_integer.dat". I tried to do this in C++ but I did not succeed. The fisrt probelm is: how can i convert a number to a char ; and how can i concanate these 2 characters ; and how to declare this final char in the right way in order to open this filename ?
Many questions but I did find an easy way to do this.
#include <string>
#include <sstream>
std::string make_filename(std::string prefix, int id) {
std::stringstream ss;
ss << prefix << "_" << id << ".dat";
return ss.str();
}
and then I convert the string to char.
if you are working with c you may try the function described in here itoa
else if you are working woth c++ you may try something like this:
#include <sstream>
int i = 5;
std::string s;
std::stringstream out;
out << i;
s = out.str();
Related
It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For help clarifying this question so that it can be reopened, visit the help center.
Closed 10 years ago.
This is probably easy but im not sure how. I tried searching multiple websites and yes Google and couldn't find anything on this.
My vector result[0] looks like this
A3 * * B4 * *
Declaration
vector<string> result = v.formVectorFile("Prj3 Config.txt");
I know that cin reads until whitespace so I was trying to use this to figure it out.
If I read straight from fstream I can read until whitespace, but im trying to do this with a string inside a vector and something like result[0] >> s; obviously doesnt work.
I need to read until it hits a whitespace then read the next one until whitespace. Etc...
So extract A3 by itself. Operate on it then extract * etc...
Your question is unclear because you don't tell us precisely what result is.
If we can assume that result is a std::vector<std::string>, then you can do something like this:
std::istringstream iss(result[0]); // consider only first string in vector
std::string item;
while(iss >> item) {
std::cout << "I found: " << item << "\n";
}
If we assume that result is std::vector<char>, then you can do this:
std::string s(result.begin(), result.end()); // consider entire vector as single string
std::istringstream iss(s);
while(iss >> item) {
std::cout << "I found: " << item << "\n";
}
It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For help clarifying this question so that it can be reopened, visit the help center.
Closed 10 years ago.
Suppose I have a file opened with the C syntax
FILE* fp = fopen("whatever.txt", "w");
// Library function needs FILE* to work on
libray_function(fp);
// Now I'd like to copy the contents of file to std::cout
// How???
fclose(fp);
I would like to be able to copy the contents of that file in a C++ ostream (like a stringstream or maybe even std::cout). How can I do that?
You could use an ifstream and rdbuf():
#include <fstream>
#include <sstream>
std::ifstream in("whatever.txt");
std::ostringstream s;
s << in.rdbuf();
or:
std::ifstream in("whatever.txt");
std::cout << in.rdbuf();
You've opened the file for write. You're going to need to close it and reopen it anyway, you might as well open it however you please (as an istream if you like). Then it just depends how much you care about performance. If you actually care, you should read it in chunks (at least 512 bytes at a time). If you don't care about performance you can read one byte, spit out one byte.
Close it first.
fclose(fp);
Then open again
string line;
ifstream myfile ("whatever.txt");
if (myfile.is_open())
{
while ( myfile.good() )
{
getline (myfile,line);
cout << line << endl;
}
myfile.close();
}
It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For help clarifying this question so that it can be reopened, visit the help center.
Closed 11 years ago.
I need to save images captured from camera just like
"D:\storage\img1" then I press "s" another time and program should save
"D:\storage\img2" and then
"D:\storage\img3"
so everytime I press a custom key it will save an image with different name.
How to do that?
Thanks for all your responses
This code concatenates (adds) the value of int i to string filename. This is done through IntToStr() . And int i loops from 0 to 20 and thus creating your "dynamic name".
File output :
PhotoImage0.txt
PhotoImage1.txt
PhotoImage2.txt
..
..
PhotoImage19.txt
#include <iostream>
#include <fstream>
#include <string>
#include <sstream>
using namespace std;
string IntToStr(int n)
{
stringstream result;
result << n;
return result.str();
}
int main ()
{
ofstream PhotoImageFile;
int Number_of_files=20;
string filename;
for (int i=0;i<Number_of_files;i++)
{
filename="c:\\PhotoImage" + IntToStr(i) +".txt";
cout<< filename << " \n";
PhotoImageFile.open(filename.c_str());
PhotoImageFile << filename<<" : Writing this to a file.\n";
PhotoImageFile.close();
}
return 0;
}
On startup, iterate the folder with an 'img*.*' mask - how you do this is up to your file system API. Use string functions or a loop to extract the part of the filename representing the number and convert it to an int. Every time you need to save a file, add 1 to the int, convert back to number-string & then concat the path, "img", number-string and extension to assemble the new file spec.
It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For help clarifying this question so that it can be reopened, visit the help center.
Closed 11 years ago.
how would i do this:
Got a text file called directorycontents.txt in this directorycontents.txt there is a bunch of text each one is a filename with a filename extension i want to be able to go like this if there is a filename extension of specific characters like .txt or .png then do fprintf(stderr,"whateva");
i have looked at istream and fstream and iostream but im not really shore how to use fstream to do this
thanks
Okay, I'll just point you to the right direction and I won't post any code, as you need to try it by yourself.
First of all, read about reading files in C++. You can google it and there are tons of information about this. You can try with "how to read text file in C++", for example.
Second, prefer using ofstream and/or ifstream - this is the C++ way to do it.
Then parse the file - you can read it word by word (using istream::operator>> ) , line by line (for example with getline ) into std::string (as you're talking about file names).
And then analize the input - analize the parsed file and search for specific words in it - for example, std::string has member functions like find - I think this will be enough for your problem :)
I hope that helps. Just note, that we don't write code here, we just help finding solutions for problems.
For something like this definitely take a look at std::fstreams. Based on your vague description of what you're trying to do, you can use this simple program as a starting point:
#include <iostream>
#include <fstream>
#include <string>
using namespace std;
void doSomething();
int main(int argc, char *argv[])
{
if(argc < 2)
{
cout << "Usage: findsomething [filename]" << endl;
return 1;
}
ifstream infile(argv[1], ifstream::in);
if(!infile.is_open())
{
cout << "Couldn't open file " << argv[1] << endl;
return 1;
}
string line;
while(getline(infile, line))
{
if(line.find(".txt") != string::npos ||
line.find(".png") != string::npos ||
line.find(".bat") != string::npos)
{
doSomething();
}
}
}
Hopefully, that's enough code to get you started and it isn't too difficult for you to read.
It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For help clarifying this question so that it can be reopened, visit the help center.
Closed 11 years ago.
I ask about the function that seek in the K-th line in a text file and the one that read the text file by line or by character in C++! knowing that i'm working with borland.
fpeek is an open source application that does exactly that. Check the sources and see how its done.
I took a quick look and I believe you'll end up with something like this (I haven't tested this code):
std::ifstream file(filename);
std::string line;
int pos = 1;
while (std::getline(file, line))
{
// Find if current line should be displayed
if (15 == pos) // looking for the 15th line in the file
{
std::cout << pos << ": " << line << std::endl;
}
pos++;
}