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226 lines
10 KiB
226 lines
10 KiB
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Name
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m4 - Invokes a macro processor.
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Syntax
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m4 [ option... ] [ file... ]
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Description
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M4 is a macro processor intended as a front end for Ratfor,
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C, and other languages. Each of the argument files is
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processed in order; if there are no files, or if a filename
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is -, the standard input is read. The processed text is
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written on the standard output.
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The options and their effects are:
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-e Operates interactively. Interrupts are ignored and the
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output is unbuffered.
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-s Enables line sync output for the C preprocessor (#line
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...)
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-Bint
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Changes the size of the push-back and argument
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collection buffers from the default of 4,096.
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-Hint
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Changes the size of the symbol table hash array from
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the default of 199. The size should be prime.
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-Sint
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Changes the size of the call stack from the default of
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100 slots. Macros take three slots, and nonmacro
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arguments take one.
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-Tint
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Changes the size of the token buffer from the default
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of 512 bytes.
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To be effective, these flags must appear before any
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filenames and before any -D or -U flags:
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-Dname[=val]
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Defines name to val or to null in val's absence.
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-Uname
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Undefines name.
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Macro Calls
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Macro calls have the form:
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name(arg1,arg2, ..., argn)
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The left parenthesis (() must immediately follow the name of
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the macro. If a defined macro name is not followed by a
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left parenthesis ((), it is deemed to have no arguments.
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Leading unquoted blanks, tabs, and newlines are ignored
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while collecting arguments. Potential macro names consist
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of alphabetic letters, digits, and underscore _, where the
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first character is not a digit.
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Left and right single quotation marks are used to quote
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strings. The value of a quoted string is the string
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stripped of the quotation marks.
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When a macro name is recognized, its arguments are collected
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by searching for a matching right parenthesis. Macro
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evaluation proceeds normally during the collection of the
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arguments, and any commas or right parentheses which happen
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to turn up within the value of a nested call are as
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effective as those in the original input text. After
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argument collection, the value of the macro is pushed back
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onto the input stream and rescanned.
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M4 makes available the following built-in macros. They may
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be redefined, but once this is done the original meaning is
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lost. Their values are null unless otherwise stated:
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define The second argument is installed as the value of
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the macro whose name is the first argument.
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Each occurrence of $n in the replacement text,
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where n is a digit, is replaced by the n-th
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argument. Argument 0 is the name of the macro;
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missing arguments are replaced by the null
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string; $# is replaced by the number of
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arguments; $* is replaced by a list of all the
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arguments separated by commas; @ $@ is like $*,
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but each argument is quoted (with the current
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quotation marks).
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undefine Removes the definition of the macro named in its
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argument.
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defn Returns the quoted definition of its
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argument(s). It is useful for renaming macros,
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especially built-ins.
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pushdef Like define, but saves any previous definition.
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popdef Removes current definition of its argument(s),
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exposing the previous one if any.
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ifdef If the first argument is defined, the value is
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the second argument, otherwise the third. If
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there is no third argument, the value is null.
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shift Returns all but its first argument. The other
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arguments are quoted and pushed back with commas
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in between. The quoting nullifies the effect of
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the extra scan that will subsequently be
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performed.
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changequote Changes quotation marks to the first and second
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arguments. The symbols may be up to five
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characters long. Changequote without arguments
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restores the original values.
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changecom Changes left and right comment markers from the
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default # and newline. With no arguments, the
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comment mechanism is effectively disabled. With
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one argument, the left marker becomes the
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argument and the right marker becomes newline.
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With two arguments, both markers are affected.
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Comment markers may be up to five characters
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long.
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divert M4 maintains 10 output streams, numbered 0-9.
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The final output is the concatenation of the
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streams in numerical order; initially stream 0
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is the current stream. The divert macro changes
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the current output stream to its (digit-string)
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argument. Output diverted to a stream other
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than 0 through 9 is discarded.
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undivert Causes immediate output of text from diversions
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named as arguments, or all diversions if no
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argument. Text may be undiverted into another
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diversion. Undiverting discards the diverted
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text.
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divnum Returns the value of the current output stream.
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dnl Reads and discards characters up to and
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including the next newline.
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ifelse Has three or more arguments. If the first
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argument is the same string as the second, then
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the value is the third argument. If not, and if
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there are more than four arguments, the process
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is repeated with arguments 4, 5, 6 and 7.
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Otherwise, the value is either the fourth
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string, or if it is not present, null.
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incr Returns the value of its argument incremented by
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1. The value of the argument is calculated by
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interpreting an initial digit-string as a
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decimal number.
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decr Returns the value of its argument decremented by
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1.
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eval Evaluates its argument as an arithmetic
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expression, using 32-bit arithmetic. Operators
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include +, -, *, /, %, ^ (exponentiation),
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bitwise &, |, ^, and ~; relationals;
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parentheses. Octal and hex numbers may be
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specified as in C. The second argument
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specifies the radix for the result; the default
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is 10. The third argument may be used to
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specify the minimum number of digits in the
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result.
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len Returns the number of characters in its
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argument.
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index Returns the position in its first argument where
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the second argument begins (zero origin), or -1
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if the second argument does not occur.
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substr Returns a substring of its first argument. The
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second argument is a zero origin number
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selecting the first character; the third
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argument indicates the length of the substring.
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A missing third argument is taken to be large
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enough to extend to the end of the first string.
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translit Transliterates the characters in its first
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argument from the set given by the second
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argument to the set given by the third. No
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abbreviations are permitted.
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include Returns the contents of the file named in the
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argument.
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sinclude Identical to include, except that it says
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nothing if the file is inaccessible.
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syscmd Executes the XENIX command given in the first
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argument. No value is returned.
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sysval Is the return code from the last call to syscmd.
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maketemp Fills in a string of XXXXX in its argument with
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the current process ID.
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m4exit Causes immediate exit from m4. Argument 1, if
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given, is the exit code; the default is 0.
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m4wrap Argument 1 will be pushed back at final end-of-
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file; for example, m4wrap(`cleanup()').
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errprint Prints its argument on the diagnostic output
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file.
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dumpdef Prints current names and definitions, for the
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named items, or for all if no arguments are
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given.
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traceon With no arguments, turns on tracing for all
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macros (including built-ins). Otherwise, turns
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on tracing for named macros.
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traceoff Turns off trace globally and for any macros
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specified. Macros specifically traced by
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traceon can be untraced only by specific calls
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to traceoff.
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