m4(1) m4(1)NAME m4 - macro processor SYNOPSIS m4 [-Bint] [-e] [-Hint] [-s] [-Sint] [-Tint] [-Dname[=val]] [-Uname] [file...] DESCRIPTION m4 is a macro processor intended as a front end for C and other languages. Each of the argument files is processed in order. If there are no files or if a filename is -, the standard input is read. The processed text is written on the standard output. FLAG OPTIONS The flag options and their effects are as follows: -Bint Change the size of the push-back and argument collec- tion buffers from the default of 4096. -e Operate interactively. Interrupts are ignored and the output is unbuffered. -Hint Change the size of the symbol table hash array from the default of 199. The size should be prime. -s Enable line sync output for the C preprocessor (#line...). -Sint Change the size of the call stack from the default of 100 slots. Macros take 3 slots, and nonmacro argu- ments take 1. -Tint Change the size of the token buffer from the default of 512 bytes. To be effective, the flag options noted above must appear before any filenames and before any -D or -U flags: -Dname[=val] Define name to val or to null in the absense of val. -Uname Undefine name. Macro calls have the form: name(arg1,arg2,...,argn) The right parenthesis, (, must immediately follow the name of the macro. If the name of a defined macro is not fol- lowed by a (, it is deemed to be a call of that macro with no arguments. Potential macro names consist of alphabetic April, 1990 1
m4(1) m4(1)letters, digits, and underscore (_), where the first charac- ter is not a digit. Leading unquoted blanks, tabs, and newlines 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 ar- guments 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 that happen to turn up within the value of a nested call are as effective as those in the original input text. After the argument collection, the value of the macro is pushed back onto the input stream and rescanned. Built-in Macros 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 Install the second argument 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 nth argument. Argument 0 is the name of the macro; missing arguments are replaced by the null string; $# is replaced by the number of arguments; $* is replaced by a list of all the arguments separated by commas; $@ is like $*, but each argument is quoted (with the current quotes). undefine Remove the definition of the macro named in the argument. defn Return the quoted definition of the argument(s). This macros is useful for renam- ing macros, especially built-in macros. pushdef Similar to define, but also save any previous definition. popdef Remove the current definition of the argument(s), exposing the previous one, if any. ifdef If the first argument is defined, install the second argument as its value; otherwise, in- stall the third argument. If there is no third argument, the value is null. The word unix is 2 April, 1990
m4(1) m4(1)predefined on the UNIX(Reg.) system versions of m4. shift Return all but the first argument. The other arguments are quoted and pushed back with com- mas in between. The quoting nullifies the ef- fect of the extra scan that is subsequently performed. changequote Change quote symbols to the first and second arguments. The symbols may be up to five char- acters long. changequote without arguments re- stores the original values, that is, ``''. changecom Change left and right comment markers from the default # and newline. With no arguments, the comment mechanism is effectively disabled. With one argument, the left marker becomes the argument and the right marker becomes newline. With two arguments, both markers are affected. Comment markers may be up to five characters long. divert Change the current output stream to its (digit-string) argument. m4 maintains 10 out- put streams, numbered 0-9. The final output is the concatenation of the streams in numerical order; initially stream 0 is the current stream. 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 there is no argument. Text may be undiverted into another diversion. Undiverting discards the diverted text. divnum Return the value of the current output stream. dnl Read and discard characters up to and including the next newline. ifelse Has three or more arguments. If the first ar- gument 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 pro- cess is repeated with arguments 4, 5, 6, and 7. Otherwise, the value is either the fourth string or, if it is not present, null. incr Return the value of the argument incremented by 1. The value of the argument is calculated by April, 1990 3
m4(1) m4(1)interpreting an initial digit-string as a de- cimal number. decr Return the value of the argument decremented by 1. eval Evaluate the argument as an arithmetic expres- sion, using 32-bit arithmetic. Operators in- clude +, -, *, /, %, ^ (exponentiation), bit- wise &, |, ^, and ~ as well as relationals and parentheses. Octal and hexidecimal numbers may be specified as in C. The second argument specifies 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 Return the number of characters in the argu- ment. index Return the position in the first argument where the second argument begins (zero-origin), or -1 if the second argument does not occur. substr Return a substring of its first argument. The second argument is a zero-origin number select- ing the first character; the third argument in- dicates the length of the substring. A missing third argument is taken to be large enough to extend to the end of the first string. translit Transliterate the characters in the first argu- ment from the set given by the second argument to the set given by the third. No abbrevia- tions are permitted. include Return the contents of the file named in the argument. sinclude Same as include, except that nothing is re- turned if the file is inaccessible. syscmd Execute the system command given in the first argument. No value is returned. sysval Is the return code from the last call to syscmd. maketemp Fill in a string of XXXXX in the argument with the current process ID. m4exit Cause immediate exit from m4. Argument 1, if 4 April, 1990
m4(1) m4(1)given, is the exit code. The default is 0. m4wrap Push back argument 1 at final EOF. An example is: m4wrap(`cleanup()'). errprint Print the argument on the diagnostic output file. dumpdef Print current names and definitions for the named items, or for all items if no arguments are given. traceon With no arguments, turn on tracing for all mac- ros, including built-ins. Otherwise, turn on tracing for named macros. traceoff Turn off tracing globally and for any macros specified. Macros specifically traced by tra- ceon can be untraced only by specific calls to traceoff. EXAMPLES m4 file1 file2 > outputfile runs the m4 macro processor on the files file1 and file2 and redirects the output into outputfile. FILES /usr/bin/m4 SEE ALSO cc(1), cpp(1). ``m4 Reference,'' in A/UX Programming Languages and Tools, Volume 2. April, 1990 5