Linux in a Nutshell, Fifth Edition

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Chapter 3: Linux Commands

This is the Title of the Book, eMatter Edition

Copyright © 2006 O’Reilly & Associates, Inc. All rights reserved.

Directives

All cpp directive lines start with # in column 1. Any number of

blanks and tabs is allowed between the # and the directive. The

directives are:

#assert name (string)

Define a question called name, with an answer of string. Asser-

tions can be tested with #if directives. The predefined

assertions for #system, #cpu, and #machine can be used for

architecture-dependent changes.

#unassert name

Remove assertion for question name.

#define name token-string

Define a macro called name, with a value of token-string.

Subsequent instances of name are replaced with token-string.

#define name( arg, ... , arg ) token-string

This allows substitution of a macro with arguments. token-

string will be substituted for name in the input file. Each call to

name in the source file includes arguments that are plugged

into the corresponding args in token-string.

#undef name

Remove definition of the macro name. No additional tokens

are permitted on the directive line after name.

#ident string

Put string into the comment section of an object file.

#include "filename", #include<filename>

Include contents of filename at this point in the program. No

additional tokens are permitted on the directive line after the

final " or >.

#line integer-constant "filename"

Cause cpp to generate line-control ...