C Learning Notes

This page was created when I trying to learn GNU Autotools and realized that my C skill wasn't good enough.

Contents

• Reading materials
• Random notes

Reading materials

• C99
• GNU Coding Standards (Wikipedia)
• Indent style

Random notes

• extern to declare within function definition:

  I somehow coded to use getopt without including unistd.h and the optarg is needed, so I simply inserted the following inside at the beginning of main function:

  extern char *optarg;

  Although it works, I didn't entirely sure what really is until I read on Wikipedia:

  An external variable may also be declared inside a function. In this case the extern keyword must be used, otherwise the compiler will consider it a definition of a local variable, which has a different scope, lifetime and initial value. This declaration will only be visible inside the function instead of throughout the function’s module.