CODEWITHSUNDEEP
c++ofstream
dirtymikeandtheboys
dirtymikeandtheboys

Reputation: 541

C++ File IO persistent temporary file with tmpnam

I'm trying to create a couple of temporary files to write and read from, and then have destroyed when the program is complete. I have seen tmpfile, which would be great, but I would like to know the name of that file as well. I've read the docs for ofstream but I don't think I'm implementing things right. What I'm trying to do:

  1. Create a class that has two member variables that are type char xFile[64] and char yFile[64].
  2. In the constructor I put: std::tmpnam(xFile); std::tmpnam(yFile). This assigns a c string like /y3s3 into xFile.
  3. I use a method to open the file and add a string.
  4. xFile.good() evaluates as false every time.

On point #3, I wrote something like

void filemng::makeXCopy (std::string text) {

    // actually I've tried fsteam and ifstream as well, shot in the dark
    std::ofstream xfile(xFile, std::ofstream::out); 

    if(!xfile.good()) {
        std::cerr << "Failed to open xFile.\n";
    }

}

Of course, when I run it, I see "Failed to open xFile." I just cannot see what I'm doing wrong here.

Upvotes: 0

Views: 832

Answers (1)

Nipun Talukdar
Nipun Talukdar

Reputation: 5387

Here is an example to do it using mkstemp:

#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>

int main()
{
    char name[255] = "/tmp/mytempfile_XXXXXX";
    int fd = mkstemp(name);
    if (fd > 0) {
        printf("Created %s\n", name);
        write(fd, "some dataa\n", strlen("some dataa\n"));
        close(fd);
    } else {
        printf("Failed \n");
    }
    return 0;
}

Note that "xxxxxx" in the string passed to mkstmp will be replaced with some unique string that will make the filename unique in the directory.

Upvotes: 1

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