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#ident "%Z%%M% %I% %E% SMI"

CHANGES as of July 12:

1. \ddd allowed in regular expressions.

2. exit <expression> causes the expression to

to be the status return upon completion.

3. a new builtin called "getline" causes the next

input line to be read immediately. Fields, NR, etc.,

are all set, but you are left at exactly the same place

in the awk program. Getline returns 0 for end of file;

1 for a normal record.

CHANGES SINCE MEMO:

Update to TM of Sept 1, 1978:

1. A new form of for loop

for (i in array)

statement

is now available. It provides a way to walk

along the members of an array, most usefully

for associative arrays with non-numeric subscripts.

Elements are accessed in an unpredictable order,

so don't count on anything.

Futhermore, havoc ensues if elements are created

during this operation, or if the index variable

is fiddled.

2. index(s1, s2) returns the position in s1

where s2 first occurs, or 0 if it doesn't.

3. Multi-line records are now supported more

conveniently. If the record separator is null

RS = ""

then a blank line terminates a record, and newline

is a default field separator, along with

blank and tab.

4. The syntax of split has been changed.

n = split(str, arrayname, sep)

splits the string str into the array using

the separator sep (a single character).

If no sep field is given, FS is used instead.

The elements are array[1] ... array[n]; n

is the function value.

5. some minor bugs have been fixed.

IMPLEMENTATION NOTES:

Things to watch out for when trying to make awk:

1. The yacc -d business creates a new file y.tab.h

with the yacc #defines in it. this is compared to

awk.h on each successive compile, and major recompilation

is done only if the files differ. (This permits editing

the grammar file without causing everything in sight

to be recompiled, so long as the definitions don't

change.)

2. The program proc.c is compiled into proc, which

is used to create proctab.c. proctab.c is the

table of function pointers used by run to actually

execute things. Don't try to load proc.c with the

other .c files; it also contains a "main()".

3. Awk uses structure assignment. Be sure your

version of the C compiler has it.

4. The loader flag -lm is used to fetch the standard

math library on the Research system. It is more likely

that you will want to use -lS on yours.

run.c also includes "math.h", which contains sensible

definitions for log(), sqrt(), etc. If you don't have this

include file, comment the line out, and all will be well

anyway.

5. The basic sequence of events (in case make doesn't

seem to do the job) is

yacc -d awk.g.y

cc -O -c y.tab.c

mv y.tab.o awk.g.o

lex awk.lx.l

cc -O -c lex.yy.c

mv lex.yy.o awk.lx.o

cc -O -c b.c

cc -O -c main.c

e - <tokenscript

cc -O -c token.c

cc -O -c tran.c

cc -O -c lib.c

cc -O -c run.c

cc -O -c parse.c

cc -O -c proc.c

cc -o proc proc.c token.o

proc >proctab.c

cc -O -c proctab.c

cc -i -O awk.g.o awk.lx.o b.o main.o token.o tran.o lib.o run.o parse.o proctab.o -lm