M4(1-SVR4) RISC/os Reference Manual M4(1-SVR4)
NAME
m4 - macro processor
SYNOPSIS
m4 [options] [files]
DESCRIPTION
The m4 command is a macro processor intended as a front end
for Ratfor, C, and other languages. Each of the argument
files is processed in order; if there are no files, or if a
file name is -, the standard input is read. The processed
text is written on the standard output.
The options and their effects are as follows:
-e Operate interactively. Interrupts are ignored and
the output is unbuffered.
-s Enable line sync output for the C preprocessor
(#line ...)
-Bint Change the size of the push-back and argument col-
lection buffers from the default of 4,096.
-Hint Change the size of the symbol table hash array from
the default of 199. The size should be prime.
-Sint Change the size of the call stack from the default
of 100 slots. Macros take three slots, and non-
macro arguments take one.
-Tint Change the size of the token buffer from the default
of 512 bytes.
To be effective, these flags must appear before any file
names and before any -D or -U flags:
-Dname[=val]
Defines name to val or to null in val's absence.
-Uname undefines name.
Macro calls have the form:
name(arg1,arg2, ..., argn)
The ( must immediately follow the name of the macro. If the
name of a defined macro is not followed by a (, it is deemed
to be a call of that macro with no arguments. Potential
macro names consist of alphabetic letters, digits, and
underscore _, where the first character is not a digit.
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Leading unquoted blanks, tabs, and new-lines are ignored
while collecting arguments. Left and right single quotes
are used to quote strings. The value of a quoted string is
the string stripped of the quotes.
When a macro name is recognized, its arguments are collected
by searching for a matching right parenthesis. If fewer
arguments are supplied than are in the macro definition, the
trailing arguments are taken to be null. Macro evaluation
proceeds normally during the collection of the arguments,
and any commas or right parentheses which happen to turn up
within the value of a nested call are as effective as those
in the original input text. After argument collection, the
value of the macro is pushed back onto the input stream and
rescanned.
m4 makes available the following built-in macros. They may
be redefined, but once this is done the original meaning is
lost. Their values are null unless otherwise stated.
define the second argument is installed as the value of
the macro whose name is the first argument.
Each occurrence of $n in the replacement text,
where n is a digit, is replaced by the n-th
argument. Argument 0 is the name of the macro;
missing arguments are replaced by the null
string; $# is replaced by the number of argu-
ments; $* is replaced by a list of all the argu-
ments separated by commas; $@ is like $*, but
each argument is quoted (with the current
quotes).
undefine removes the definition of the macro named in its
argument.
defn returns the quoted definition of its
argument(s). It is useful for renaming macros,
especially built-ins.
pushdef like define, but saves any previous definition.
popdef removes current definition of its argument(s),
exposing the previous one, if any.
ifdef if the first argument is defined, the value is
the second argument, otherwise the third. If
there is no third argument, the value is null.
The word unix is predefined on UNIX system ver-
sions of m4.
shift returns all but its first argument. The other
arguments are quoted and pushed back with commas
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in between. The quoting nullifies the effect of
the extra scan that will subsequently be per-
formed.
changequote change quote symbols to the first and second
arguments. The symbols may be up to five char-
acters long. changequote without arguments
restores the original values (i.e., ` ').
changecom change left and right comment markers from the
default # and new-line. With no arguments, the
comment mechanism is effectively disabled. With
one argument, the left marker becomes the argu-
ment and the right marker becomes new-line.
With two arguments, both markers are affected.
Comment markers may be up to five characters
long.
divert m4 maintains 10 output streams, numbered 0-9.
The final output is the concatenation of the
streams in numerical order; initially stream 0
is the current stream. The divert macro changes
the current output stream to its (digit-string)
argument. Output diverted to a stream other
than 0 through 9 is discarded.
undivert causes immediate output of text from diversions
named as arguments, or all diversions if no
argument. Text may be undiverted into another
diversion. Undiverting discards the diverted
text.
divnum returns the value of the current output stream.
dnl reads and discards characters up to and includ-
ing the next new-line.
ifelse has three or more arguments. If the first argu-
ment is the same string as the second, then the
value is the third argument. If not, and if
there are more than four arguments, the process
is repeated with arguments 4, 5, 6 and 7. Oth-
erwise, the value is either the fourth string,
or, if it is not present, null.
incr returns the value of its argument incremented by
1. The value of the argument is calculated by
interpreting an initial digit-string as a
decimal number.
decr returns the value of its argument decremented by
1.
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eval evaluates its argument as an arithmetic expres-
sion, using 32-bit arithmetic. Operators
include +, -, *, /, %, ** (exponentiation), bit-
wise &, |, ^ (bitwise xor), and ~; relationals;
parentheses. Octal and hex numbers may be
specified as in C. The second argument speci-
fies the radix for the result; the default is
10. The third argument may be used to specify
the minimum number of digits in the result.
len returns the number of characters in its argu-
ment.
index returns the position in its first argument where
the second argument begins (zero origin), or -1
if the second argument does not occur.
substr returns a substring of its first argument. The
second argument is a zero origin number select-
ing the first character; the third argument
indicates the length of the substring. A miss-
ing third argument is taken to be large enough
to extend to the end of the first string.
translit transliterates the characters in its first argu-
ment from the set given by the second argument
to the set given by the third. No abbreviations
are permitted.
include returns the contents of the file named in the
argument.
sinclude is identical to include, except that it says
nothing if the file is inaccessible.
syscmd executes the UNIX system command given in the
first argument. No value is returned.
sysval is the return code from the last call to syscmd.
maketemp fills in a string of XXXXX in its argument with
the current process ID.
m4exit causes immediate exit from m4. Argument 1, if
given, is the exit code; the default is 0.
m4wrap argument 1 will be pushed back at final EOF;
example: m4wrap(`cleanup()')
errprint prints its argument on the diagnostic output
file.
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dumpdef prints current names and definitions, for the
named items, or for all if no arguments are
given.
traceon with no arguments, turns on tracing for all mac-
ros (including built-ins). Otherwise, turns on
tracing for named macros.
traceoff turns off trace globally and for any macros
specified. Macros specifically traced by tra-
ceon can be untraced only by specific calls to
traceoff.
SEE ALSO
cc(1), cpp(1).
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