[SOLVED] Authoritative descriptions of module functions in C

Turbocapitalist · 10-19-2017, 11:21 AM

I have a bit of a newb question about C modules here: how do I find the authoritative descriptions of common modules and the functions they contain?

For example printf() and sprintf() are in stdio.c. Where can I find the last word in what parameters they take and how to use them? Yes, I know those two functions. I'm wondering where I can look them up how to use them and other common modules in general.

dugan · 10-19-2017, 11:49 AM

You open the headers in /usr/include and you look at them.

Turbocapitalist · 10-19-2017, 12:05 PM

Been there, done that. I was hoping for more annotation, maybe a paragraph or two on each function.

Code:

$ grep -A 2 '[[:space:]]printf(' /usr/include/stdio.h 
int      printf(const char *, ...);
int      putc(int, FILE *);
int      putchar(int);

Is there any kind of manual page that can be generated or a reference manual somewhere?

dugan · 10-19-2017, 12:17 PM

Yep.

Code:

man 3 stdio
man 3 printf

Turbocapitalist · 10-19-2017, 12:23 PM

Ok. I picked poor examples, and was missing a package. I've added the package build-essentials and now see even a manual page for things like ftell.

So is it the case in general that C functions each get their own manual page in section 3?

astrogeek · 10-19-2017, 12:32 PM

As Dugan has indicated, manual section 3 is the place (man man):

Code:

3      C Library Functions

If you are an info user, info printf will, for example, usually return all available man pages, sometimes alternate documentation.

Turbocapitalist · 10-19-2017, 12:36 PM

Ok. Thanks to both of you.

NevemTeve · 10-19-2017, 02:01 PM

Also there is 'info libc' (or 'tkinfo libc' for GUI)

KenJackson · 10-23-2017, 04:26 PM

Some systems don't have man pages unless you explicitly install them.
Rather than figuring out what to install, you can always use your browser.
There are a number of sites that have man pages.
Here are two:

sundialsvcs · 10-25-2017, 07:49 AM

It's also worth noting that "C" has no way to know that the information in the header-file is correct. It is your responsibility to ensure that header-files needed by external libraries are, in fact, correct, and that compiler-options and linker-options are such to correctly call the subroutines in the library. Otherwise, you will witness a small thermonuclear explosion.