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.
