cpp(1) DG/UX 5.4R3.00 cpp(1)
NAME
cpp - the C language preprocessor
SYNOPSIS
/lib/cpp [ option ... ] [ ifile [ ofile ] ]
DESCRIPTION
Cpp is the C language preprocessor. Thus, the output of cpp is
designed to be in a form acceptable as input to the next pass of the
C compiler. You should specify preprocessing by using the -E or -P
option to cc(1), rather than by invoking /lib/cpp explicitly.
Cpp optionally accepts two file names as arguments. Ifile and ofile
are respectively the input and output for the preprocessor. They
default to standard input and standard output if not supplied.
Options
-P Preprocess the input without producing the line control
information used by the next pass of the C compiler.
-C By default, cpp strips C-style comments. If the -C option is
specified, all comments (except those found on cpp directive
lines) are passed along.
-Uname Remove any initial definition of name. Name is a reserved
symbol that is predefined by the particular preprocessor.
-Dname
-Dname=def
Define name as if by a #define directive. If no =def is
given, name is defined as 1. If the same name is used in both
-U and -D options, the last of these options will determine
whether or not the name is defined.
-Idir Change the algorithm for searching for #include files whose
names do not begin with / to look in dir before looking in the
directories on the standard list. Thus, #include files whose
names are enclosed in "" will be searched for first in the
directory of the file with the #include line, then in
directories named in -I options, and last in directories on a
standard list. For #include files whose names are enclosed in
<>, the directory of the file with the #include line is not
searched.
-T Forces cpp to use only the first eight characters for
distinguishing different preprocessor names. This behavior is
the same as for previous preprocessors with respect to the
length of names and is included for backward compatibility.
-Ydir Use directory dir in place of the standard list of directories
when searching for #include files.
-H Print the path names of included files (one per line) on
standard error.
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Special Names
Two special names are understood by cpp. The name LINE is
defined as the current line number (as a decimal integer) as known by
cpp, and FILE is defined as the current file name (as a C string)
as known by cpp. You can use them anywhere (including in macros)
just as any other defined name.
Directives
All cpp directives start with #. Any number of blanks and tabs are
allowed between the # and the directive. The directives are:
#define name token-string
Replace subsequent instances of name with token-string.
#define name( arg, ..., arg ) token-string
Replace subsequent instances of name followed by a (, a list
of comma-separated set of tokens, and a ) by token-string,
where each occurrence of an arg in token-string is replaced by
the corresponding set of tokens in the list. When a macro
with arguments is expanded, the arguments are placed into the
expanded token-string unchanged. After the entire token-
string has been expanded, cpp restarts its scan for names to
expand at the beginning of the newly created token-string.
Notice that there can be no space between name and the (.
#undef name
Forget the definition of name (if any).
#identstring
Put string into the .comment section of an object file.
#include "filename"
#include <filename>
Include at this point the contents of filename (which will
then be run through cpp). When you use the <filename>
notation, filename is only searched for in the standard
places. See also the -I option above.
#line integer-constant "filename"
Makes cpp generate line control information for the next pass
of the C compiler. Integer-constant is the line number of the
next line and filename is the file where it comes from. If
you omit filename, the current filename is unchanged.
#endif
Ends a section of lines begun by a test directive (#if,
#ifdef, or #ifndef). Each test directive must have a matching
#endif.
#ifdef name
The lines following will appear in the output if name has been
the subject of a previous #define without being the subject of
an intervening #undef.
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#ifndef name
The lines following will not appear in the output if name has
been the subject of a previous #define without being the
subject of an intervening #undef.
#if constant-expression
Lines following will appear in the output if the constant-
expression evaluates to non-zero. All binary non-assignment C
operators, the ?: operator, the unary -, !, and ~ operators
are legal in constant-expression. The precedence of the
operators is the same as defined by the C language.
An unary operator is also defined, which can be used in
constant-expression in these two forms: defined(name) or
defined name. This lets you use #ifdef and #ifndef in a #if
directive. In constant-expression, use only operators,
integer constants, and names that cpp knows. The sizeof
operator is not available.
#elif constant-expression
Lines following will appear in the output if and only if the
constant-expression evaluates to non-zero. All binary non-
assignment C operators, the ?: operator, the unary -,!, and ~
operators are all legal in constant-expression. The
precedence of the operators is the same as defined in the C
language. There is also a unary operator defined, which can
be used in constant-expression in these two forms: defined (
name ) or defined name. This allows the utility of #ifdef and
#ifndef in a #if directive. Only these operators, integer
constants, and names, which are known by cpp, should be used
in constant-expression. In particular, the sizeof operator is
not available.
To test whether or not either of two symbols, bob and ted, are
defined, use
#if defined(bob)|defined(ted)
#else Reverses the notion of the test directive that matches this
directive. If lines previous to this directive are ignored,
the following lines will appear in the output, and vice versa.
The test directives and the possible #else directives can be nested.
FILES
/usr/include Standard directory for #include files
DIAGNOSTICS
Cpp error messages are intended to be self-explanatory. The line
number and filename where the error occurred are printed along with
the diagnostic.
SEE ALSO
cc(1).
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NOTES
When new-line characters were found in argument lists for macros to
be expanded, previous versions of cpp put out the new-lines as they
were found and expanded. The current version of cpp replaces these
new-lines with blanks.
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