File Re-arranging programm

[Frusciante]

Hi!
I'm writing a small C program to post process a huge txt file produced by a CFD software.

The CFD creates a "from.txt" file, in which every line contains many parameters calculated by it.
I need to copy the lines that contain the information i need to another "to.txt" files.

The problem is that I don´t know how to go thru the lines of the from.txt.
Once i know how to go thru them it wouldn't be that hard to write the rest of the program.

I working on something like...

fp=fopen(filename,"r");
while(c == getchar());
if (c == \n);

... but i have no idea how to go on...

I`m a newbie in this world... hope learn a lot from you all!

[sicarie]

After you open the file, I would recommend using a test more like != EOF in your while loop, and then you can use getline() to pull the whole line in, and then parse it as a string - probably a bit easier than looking at the individual characters.

http://www.cplusplus.com/
http://www.cplusplus.com/reference/string/getline.html
http://www.cplusplus.com/doc/tutorial/files.html

PS - are you specifically constrained to C, or are you able to use C++ as well? Getline and EOF are built into C, so you should be able to use them, but the tutorials given are in C++, so you'll have to modify them a bit...

[Silent1Mezzo]

Hi!
I'm writing a small C program to post process a huge txt file produced by a CFD software.

The CFD creates a "from.txt" file, in which every line contains many parameters calculated by it.
I need to copy the lines that contain the information i need to another "to.txt" files.

The problem is that I don´t know how to go thru the lines of the from.txt.
Once i know how to go thru them it wouldn't be that hard to write the rest of the program.

I working on something like...

fp=fopen(filename,"r");
while(c == getchar());
if (c == \n);

... but i have no idea how to go on...

I`m a newbie in this world... hope learn a lot from you all!

If the line needs to contain something specific you could use strstr()

if(strstr(str1, str1) != NULL)
         //Theres a match
 

If theres a match then it means that your information is in that line.

[weaknessforcats]

You can use the getline() function to read one line of text at a time. You will need to declare a char array to hold this line of text.

You use fwrite() to write the line toi another file.

Start your research with getline() and find out how to use FILE*.

Any C textbook will have your problem as an example.