Page 2 - ANSI C: Checking for a blank line in an input file

I believe I qualify for all of these. When told the line ends were my problem, I wrote a script and tested the line ends. When told that I needed to use SEEK_SET I put my best effort into using SEEK_SET (could not get it to work, despite having 2 C books, and the power of google), when told to open it with "rb" I opened it with "rb" and tried the same approaches. When Scorpions explained to me how ungetc works, I realized what I was confused about regarding it, and was able to get that to work (what my code currently uses). And before I had anything working, after I had exhausted every method I could think of, and spent a good 4 hours trying in vain to determine if the next line is blank (something that should not be difficult) I thought of and implemented an alternative, a crappy alternative yes, but it did work. And even after I had this working code, I went back and revisited the topic after Scorpions post, and was able to get that previous method to work, and ended up replacing my string method with the ungetc method.

I spent about 6 hours on this process, the only hurdle was the question: "is the next line blank"

Perhaps my perspective is off, and such a question does require extensive amounts of time, and a mere 6 hours is nothing compared to what I should have put in. But based on the commonality such a question must surely possess, I strongly suspect this is not the case.

I certainly hope so, I will be using C++ during the Fall. I am open to choices, more choices offer more methods around hurdles, and some are inevitably better than others, the concept of more efficient or more capable code is very appealing to me, and so more choices is preferable. Of course, with more choices comes more confusion, so I sincerely hope C++ is better documented than C.

Well, the course is data structures and algorithms, and I do like data structures and algorithms, C is the language used to teach the course, so it is necessary to learn what I enjoy. Like most things in life, it is a balance. As for Sizablegrin's newline function, I do not use code that I do not understand, I will figure out how/why it works before I ever use it, otherwise when I encounter a problem, I will not know the source of the problem. I have had to create several standard library functions as a result of this (again, I cannot find standard library function's code documented despite looking for it, and asking my instructor). In regards to using his code, I do not expect he would provide it if he did not want me to use it. I have never understood the ownership of thoughts, perhaps someday in the future.

I do not know where you came up with this idea that I am lazy, I have tried everything suggested in this thread, I think you are merely put off by how much I hate C. If it helps, know that I do absolutely love data structures and algorithms, my best experiences in school this semester have been in this course. When my instructor told me I could not use a binary search on a linked list, and I worked every day for about 2 weeks until I got it to work, this last program was quite enjoyable, hash tables are the most interesting thing I have done with computers in quite a while. Earlier while working on Project Euler (which eventually led to my decision to abandon C) I wrote 3 programs to find prime numbers, and the idea behind the third one was the most complicated thing I had done up to that point, with somewhat abstract thought processes behind it (certainly the most abstract programming idea I've personally ever thought of)... I almost had an orgasm when it worked.

So I am sorry that my dislike for C puts you off, and I am sorry that you have gotten the impression that I am lazy, just know that I do thoroughly enjoy the concepts behind the code, and that my motivation is not hindered my that dislike.

Documentation is all over the web (and not hard to find). A decent compiler usually has it also.

If you would read the documentation for fgets you would discover that a newline, if present, is always at the end. Consequently, if you remove all \r and \n from the end of the string, and the string is then of zero length, you have a blank line.

There is little penalty in modern systems for using single-character reads, such as you attempted, simply because most modern systems read and cache the entire file (or as much as they can). In a lesser system such actions would incur a horrible penalty because file operations are orders of magnitude slower than memory accesses.

Tossing in seeks (particularly one- or two-character movements) where they are absolutely unnecessary is also a questionable decision.

There are algorithms and there are languages and there are the systems. With enough abstraction one can forget about the systems, but one will never be an optimal user if one does so.

Thank you, can you suggest a place with good documentation? My book and most sites I find usually simply state how the function is declared, and have at most a simple paragraph explaining how to use it.

At one time I had found a wonderful site that had example code using each library function, but I did not bookmark it because I did not realize the rarity and utility of the site (I've since searched for it probably ten different times to no avail).

I would also absolutely love to see how the library functions are written. I've rewritten a few when I was unable to locate errors in my code and could not rule out the functions, it would be nice to compare them, as well as to learn. I'm particularly curious how the printf function works because I want to figure out how to dynamically send different numbers of variables to the function.

I use gcc on Ubuntu, is there a suggested method to check if it documents these functions (I'm rather new to linux as well).

Anyway, I appreciate the help in this thread, if I need to continue using C, I'll try to locate an in depth explanation of how files and file pointers work (if I can find the code for the functions that deal with this, I'll dissect that as well)

I don't know Ubuntu. I suspect, like most distros, it incorporates a manual called the "man pages". From the command-line type "man fopen", "man fgets", etc. You might even try "man man."

I cannot believe that you suggested that C is not well documented! It has an ISO standard that defines it. Note that the standard library and the language itself are different things. So you need to be clear which you are referring when asking for documentation.

www.cplusplus.com has a comprehensive and detailed description of the C library. Don't be put off by the fact that it is C++ oriented. The only thing you need to be aware of is that in C++, C library headers have no extension and are prefixed with 'c', so <cstdio> should be replaced with <stdio.h> for example. In fact all the examples use the C form, which is also valid but deprecated in C++. I believe all the C library examples are purely C code and use no C++ specific syntax.

Another reasonably good library reference is www.cppreference.com. It is less user friendly perhaps that cplusplus.com, but fills some gaps perhaps. Again don't be put off by teh name, it covers the C library (which is a subset of the C++ library - if you did not know that then that may explain why you had trouble finding documentation).


A most comprehensive and up-to-date, but perhaps less user friendly library reference is www.dinkumware.com friendly.

In the end C is not a big language, and is not well served by a big reference. You would do well to get yourself a copy of "The C Programming Language" by Kernighan and Ritchie (often referred to as just K&R).

Documentation on both the language and the libraries can be found at http://publications.gbdirect.co.uk/c_book/. There are other tutorial resources you might consider listed at http://en.wikipedia.org/wiki/C_(pro...uage)#Tutorials .

Clifford

Actually since Ubuntu is designed for users first, rather than programmers, it only installs part of the man pages by default. For programming, you'll need to install the following packages:

manpages-dev
manpages-posix
manpages-posix-dev

You can do this by using the Synaptics package manager or going to the command line and typing:
sudo apt-get install manpages-dev
and do the same thing for the other two packages.