What is main in c language program

I insert a comment with a XXX prefix and a short remark describing what needs to be done. It doesn't matter what you use, just make sure it's not likely to show up in your codebase in another context, as a function name or variable, for instance.

OK, this program still does almost nothing when you compile and run it. But now you have a solid skeleton to build your own command line parsing C programs. Now you're ready to write C that will be easier to maintain. If you have any questions or feedback, please share them in the comments.

Always keep the API in close association to its code. While I would normally agree with you, the scope of this article was how to write a main. I guess I know what to write about next :. It will definitely be a good next article! Here are a few other ideas Another good topic would be debugging, a few examples how you debug code than a program was coredumped and killed with different signals.

You also touched slightly "errno is used as an out-of-band communication channel by the standard C library to communicate why a function might have failed". I think, it deserves its own article.

Tell us more how you handle errors. I really like a style of the text and the content in particular. It is uniq as it represents a distilled experience.

There is no only one right solution. C is still C, but knowing the language doesn't mean everyone will use it in the same way. Experience matters. Thank you for the praise and you are of course correct with respect to the opt argument being unused in the body of the function.

I had intended to emit the offending option in the fprintf but must have forgotten it in the fugue of writing. I couldn't compile the code because of two issues: 1. After I fixed these two issues, I've managed to compiled the code.

And, one little note about a formatting of the usage output. This is a good start, but there is one glaring omission. Once that is added, you might want to be able to set a log level as well, although the verbose counter would work if you use multiple 'v's. One of the biggest problems I encountered in debugging new code is to figure out what lead up to the crash.

Single stepping through a loop that repeats thousands of time before it crashes is not fun. Plus the debugger changes the timing and it may not crash at all.

A log file with a few simple breadcrumbs can work wonders in this case. Thanks for the suggestion Bob, however I have to wonder how redirecting stderr to a file in a shell doesn't accomplish the same thing without code maintenance overhead?

I'm not saying you're wrong to want log files, but I am always interested in writing only as much code as I need to get the job done and no more. Can you guarantee that doing it in the shell won't add a layer of kernel calls for each write? If not, there may be a significant difference in the time to push each message out to the file. When I first ran into this one, it took me three days to figure out the redirect was slowing the process down enough that the crash no longer occurred.

With the log file it still didn't happen often, but at least I was able to find the glitch. Timing is everything. Thanks for sharing your experience; fixing heisenbugs can be notoriously difficult to accomplish. I think we can agree that the function and file layout I present in this article can be adapted to fit debugging that class of problems, however my primary purpose writing this article is to demonstrate basic structure of a C program for those who are just beginning their journey.

While C is replete with instances of "magic constants", I find it's better to use a macro definition for constants whenever possible. And I especially like using constants that the standard library supplies since I know that I can count on them being defined in compliant runtime environments. Awesome, thanks! If I may complete the "usage" function by using the 'opt' argument so the message be more informative when encountering an error, I propose this:. All those are worthy additions and illustrate what can happen when you build on a solid foundation; you can begin to concentrate on those small usability touches that are easy but mean a great deal to the users of your tools.

Ok, I'm not even going to try to lie. It just goes to show that editing is hard when there isn't a compiler keeping you honest. Thanks for the extra editing, your check is in the mail! However everything worked fine on MacOS.

However a more elegant approach is to add simply an " include. My comment was supposed to be instructive and helpful for RedHat users. In this case completely removing the essence of my message. However a much more elegant approach is to add simply an include lt stdint.

Welcome to the unbounded joy that is C! Today's programming environments are much more fluid and you have to decide how much you want to "forage" from the environment and how much you are willing to re-implement to avoid the problems like the one you encountered. You mentioned somewhere Solaris. I worked for ten years for Sun Microsystems At the time X86 and Linux were foul words at Sun, but I secretly still did it in my basement.

I worked in the Austin TX office from to doing performance work and x86 was definitely a dirty word for a long time at Sun. I spent the majority of my time working on SPARC hardware with some weird jaunts from time to time AMD, firmware, service processors, architecture simulators, stuff like that.

It's a nice article to how to write a good C-Program and i learnt a few new things related to C programming.

Did I miss a return somewhere? Since you mention that you also code in Python, is it too much to ask for essentially the same template using Python's standard libraries?

Pretty please with sugar on top?! How to write a good C main function How to write a good C main function. Learn how to structure a C file and write a C main function that handles command line arguments like a champ. Get the highlights in your inbox every week. Let's do this. These are bits of Unix history, that I won't repeat here Secondly, there are only a few valid signatures for main anyway, and you normally won't call main within your code unless you're writing an entry for the IOCCC.

Longer answer: this is how your program indicates success or failure to the host environment. An individual implementation is free to support additional signatures for main , but it must document those additional signatures. If your compiler documentation does not list void main as a legal signature, then you shouldn't use it. Exactly what value corresponds to what status is up to the implementation.

The main function is implicitly called by the C library by recognizing the in-built keyword 'main'. So we don't need to declare a prototype for main function. This I am not sure, but I think it depends on the type of editor used. In Turbo C , void main will be accepted, whereas in dev-cpp main should return a value. Simply put most essence for all of your questions is traditions and conformance. Toolchains, operating systems, etc know that way that this procedure called main , must be called out first from the user code space program Now specifically: 1 Because of the conformance as I said.

You do not need to declare because toolchains and operating systems know already about main. Also there are other conformance functions like exit. Usually non zero means error. So when U are using scripts or other programs calling out your program e. But actually you can interpret that value how you want it. But as I said OS can have the result. BUT actually operating systems and tool chains facilitate other calls before your main, to setup environment, do the initialization or whatever.

But you do not know about that directly when you are writing your code and you do not have to deal with that and think about that at all. In embedded systems there will be usually some very low level functions called to setup the CPU main clock, interrupts, stack, etc. Some of the tool chains like IAR actually can enable you to execute your own code before main is called. Functions need not necessarily be declared first as a prototype.

Such a declaration is needed only if we need to use a function before it is defined. The meaning of the value returned from main is conventional. The convention generally accepted is that 0 is considered success, and not 0 some kind of failure. When we run a C program, Computers control passes over to the C programs main function, From there itself the C program starts to execute. Stack Overflow for Teams — Collaborate and share knowledge with a private group.

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