Test for file

cxel91a · 04-11-2003, 09:45 PM

I'm trying to create a mini program to copy
a file using C++ on a linux system. Can
someone tell me how to verify that a
file is present before calling ifstream object.

rmartine · 04-11-2003, 10:42 PM

Use the open() command. If I remember correctly if you chose not to create the non-existent file it will return a -1.

Good Luck

cxel91a · 04-12-2003, 11:13 AM

That only works for ofstream object creating files, not ifstream.

GtkUser · 04-12-2003, 01:25 PM

Code:

#include<iostream>
#include<fstream>
#include<string>

int main() {
  std::ofstream outfile("outfilename");
  std::ifstream infile("infilename");

  if ( ! infile ) {
  std::cerr << "Error message - no file" << std::endl;
  return -1;
  }

  if(! outfile) {
  std::cerr << "Error message" << std::endl;
  return -2;
  }

  std::string word;
  while ( infile >> word ) outfile << word << ' ';

  return 0;
}

cxel91a · 04-12-2003, 01:57 PM

I had that part of it. The goal is to get the src file from the user. If a non-existing file was given the output was an empty file.
I want to try and test for an actual file on the system before passing in the file name.

I'm looking for the syntax to perform the similar function to

if [ -z fileName ]; then
$action

Mik · 04-14-2003, 07:55 AM

You should use the system call stat for that. Read the man pages to find out how to use it.

cxel91a · 04-15-2003, 11:23 AM

Thanks