README

This is mawk 1.9.9.x, a beta release for 2.0.0.

I first released mawk 1.0 in 1991 and last released mawk 1.3.3 in 1996.
(A few people had mawk 1.3.3.1 with nextfile, 1999.)

Why a 25 and 20 year anniversary release?  Because I always knew a
few things could be done better and design decisions that were right for 
the 90's were wrong for 21st century.

In my absence, there have been other developers that produced mawk 1.3.4-xxx.
I started from 1.3.3 and there is no code from the 1.3.4 developers in
this mawk, because their work either did not address my concerns or
inadequately addressed my concerns or, in some cases,
was wrong.  I did look at the
bug reports and fixed those that applied to 1.3.3.
I did switch to the FNV-1a hash function as suggested in a bug report.

Here is what is new.

(1) Oddly written but legal regular expressions could cause exponential
blowup of execution time versus input length.
Consider,

      mawk '!/(a|aa)*Z/'    aN

where the contents of file aN  is one line with N a's and terminated with X.
E.g.,
        a5       is       aaaaaX
	a10      is       aaaaaaaaaaX
	a20      is       aaaaaaaaaaaaaaaaaaaaX
	etc


On a 5000 bogomips box, using mawk133, times are:

a5          .002  sec
a20         .005
a40         53.2  sec
a50         1 hour 41 min
a1000       more seconds than there are atoms in the universe

This released mawk does a1000 in .005 seconds.

For reasonably written regular expressions and normal input, this
bug for most people never came up.  In that sense, it is a minor bug.
However in the sense that a regular expression algorithm should 
have linear execution time relative to the input length in all
cases, it was a major error by me.

(2)  Fixed limit on number of fields, $1 $2 ... is removed.

(3)  Fixed limit on length of a string produced by sprintf() is removed.

(4)  Sizes chosen for 1991-96 have been adjusted for the 21st century.
Most important, the input buffer is bigger and grows faster to handle
long input records.  The memory allocator blocks are bigger.
The hash tables have more slots.

(5) gsub() is no longer recursive which makes it faster and more
reliable.  ^ is handled correctly.

(6) printf and sprintf handle bigger integers. For example,

$ mawk 'BEGIN{ printf "%x %x %d\n", -1, 2^63, -2^63}'
ffffffffffffffff 8000000000000000 -9223372036854775808

Awk prints an integer as an integer (%d) and other numbers
using OFMT (default to %.6g).  The new mawk recognizes bigger integers.

$ mawk133 'BEGIN { print 2^33}'
8.58993e+09

$ mawk 'BEGIN { print 2^33}'
8589934592

In this area, there is a mild disagreement between gawk and mawk.

$ mawk 'BEGIN { print exp(37)}'
1.17191e+16

$ gawk 'BEGIN { print exp(37)}'
11719142372802612

Actual value is
11719142372802611.3086...

(7)  The character '\0' (zero) can be an element of a string.

(8) Design of arrays was simplified. No effect from user perspective,
but more maintainable from developer perspective.

(9) nextfile

(10) length(A) where A is an array returns the number of elements in the
array.

(11) Backslash in replacement strings.  

$ echo ABC | mawk133 '{sub(/B/,"\\\\") ; print}'
A\C

$ echo ABC | mawk '{sub(/B/,"\\\\") ; print}'
A\\C

The 133 behavior follows the early 90's posix spec, but it is confusing
that a string without & is altered.  Gawk and Kernighan's awk do it
differently and now mawk agrees with them.

\ escapes \ and \ escapes &, but only if the run of \ ends in &.

For example,

$ echo ABC | mawk '{sub(/B/,"\\\\&") ; print}'
A\BC

(12) Some years ago, 

$ echo 0x4  inf nan | awk '{ print 7 + $1, 8 + $2, 9+$3}'
7 8 9

for all awk's, but now

$ echo 0x4  inf nan | mawk133 '{ print 7 + $1, 8 + $2, 9+$3}'
11 inf nan

What changed was the C-library strtod() started recognizing "inf", "nan"
and hex strings.  But changes for a low level C library, are not
right for a high level language like awk.  So, in agreement with
gawk, the new mawk gives the old result.

$ echo 0x4  inf nan | mawk '{ print 7 + $1, 8 + $2, 9+$3}'
7 8 9

(13)  Regular expression character classes such as /[[:digit:]]/
are now supported.
The complete list is alnum, alpha, blank, cntrl, digit, graph,
lower, print, space, upper, xdigit.

------------------------------------------------------
TBD.  The man pages need updating.