今天看别人写的程序，遇到函数，常量找不到头文件的错误，在windows中好解决，在linux下看书看到了，所以摘下来供以后察看
摘自：Beginning.Linux.Programming,Third.Edition
It’s often convenient to use the grep command to search header files for particular definitions and function
prototypes. Suppose we need to know the name of the #defines used for returning the exit status
from a program. Simply change to the /usr/include directory and grep for a probable part of the
name like this:
$ grep EXIT_ *.h
...
stdlib.h:#define EXIT_FAILURE 1 /* Failing exit status. */
stdlib.h:#define EXIT_SUCCESS 0 /* Successful exit status. */
...
$
Here grep searches all the files in the directory with a name ending in .h for the string EXIT_. In this
example, it has found (among others) the definition we need in the file stdlib.h.
