C++, cin from file, output to a file

[Sharpiedeluxe]

Okay, so I'm writing this program, and basically I want to test it with a bunch of text files, and make sure that the output is valid. So, I've been using

$ a.out < test.file > test.output 2> test.error

this is correct right? However, when I compare files, it appears that test.file is completely blank with nothing inside, as if it wasn't even taking stdin at all. However, if I run the program, immediately it prompts for input. Any suggestions? the code generally looks like:

while (!cin.eof())
{
cin >> user_data;
cin >> user_data2;
}

this is the only thing in the code that I would see a problem with :( Any help would be great. Thanks.

edit: Just found out that I get this if I output to an error file "<stdin>:106: warning: no newline at end of file", unfortunately, if its complaining about line 106, that's right in the middle of some code, so adding more lines doesn't help.

[bfhicks]

I have a little trick you might like.

When first writing the program, I just want to compile & run, not worry about providing input. So, I add two lines to the top of my code.




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

using namespace std;

ifstream fin("cube.txt");
#define cin fin

int main()
{
string line;
while (getline(cin,line))
{
cout << line << endl;
}

return 1;
}


To run this, I'll do:

./test
Then, I can check the output as it prints out to verify it.

Now, I'm ready to script it to run with a bunch of files, then I'll comment out two lines:

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

using namespace std;

//ifstream fin("cube.txt");
//#define cin fin

int main()
{
string line;
while (getline(cin,line))
{
cout << line << endl;
}

return 1;
}

Run program: provide input and save the output.

./test < cube.txt > cube_out.txt

[dribeas]

$ a.out < test.file > test.output 2> test.error

this is correct right? However, when I compare files, it appears that test.file is completely blank with nothing inside, as if it wasn't even taking stdin at all.

Just to make sure we are clean on redirections: when you redirect input _from_ a file, the file must have the contents before hand, they are read and passed to the program as if a user was just typing those same characters on the console.



$ cat > file.txt << EOF
This is a file
with three lines
and this is the third line.
EOF
$ cat < file.txt # uses file.txt as user input
This is a file
with three lines
and this is the third line.
$ cat < file.txt > file2.txt # creates file2.txt with the output above
$ cat file2.txt # checks the contents of newly created file2.txt
This is a file
with three lines
and this is the third line.

[Sharpiedeluxe]

Right, I made sure that the input files were correct (no newlines at the bottom), and that I could cat them to the terminal. However, I renamed all the files with different extensions. Previously, they were .file, and after naming them to .txt, they all worked with the program. :confused: Doesn't make too much sense to me unfortunately xD But thanks for all the help.