A2P(1)           Perl Programmers Reference Guide          A2P(1)

       a2p - Awk to Perl translator

       aa22pp [[ooppttiioonnss]] ffiilleennaammee

       A2p takes an awk script specified on the command line (or
       from standard input) and produces a comparable perl script
       on the standard output.


       Options include:

            sets debugging flags.

            tells a2p that this awk script is always invoked with
            this --FF switch.

            specifies the names of the input fields if input does
            not have to be split into an array.  If you were
            translating an awk script that processes the password
            file, you might say:

                    a2p -7 -nlogin.password.uid.gid.gcos.shell.home

            Any delimiter can be used to separate the field

            causes a2p to assume that input will always have that
            many fields.

       --oo   tells a2p to use old awk behavior.  For now, the only
            difference is that old awk always has a line loop,
            even if there are no line actions, whereas new awk
            does not.


       but it usually does pretty well.  There are some areas
       where you may want to examine the perl script produced and

       expression to force numeric interpretation, even though
       the argument is always integer anyway.  This is generally
       unneeded in perl, but a2p can't tell if the argument is
       wish to remove it.

       Perl differentiates numeric comparison from string
       comparison.  Awk has one operator for both that decides at
       complete job of awk emulation at this point.  Instead it
       guesses which one you want.  It's almost always right, but
       it can be spoofed.  All such guesses are marked with the
       You might want to run at least once with the --ww switch to
       have used eq.

       Perl does not attempt to emulate the behavior of awk in
       which nonexistent array elements spring into existence
       simply by being referenced.  If somehow you are relying on
       this mechanism to create null entries for a subsequent

       If a2p makes a split line that assigns to a list of
       want to rerun a2p using the --nn option mentioned above.
       This will let you name the fields throughout the script.
       If it splits to an array instead, the script is probably
       referring to the number of fields somewhere.

       The exit statement in awk doesn't necessarily exit; it
       do contortions within the END block to bypass the block
       under such circumstances can be simplified by removing the
       conditional in the END block and just exiting directly
       from the perl script.

       Perl has two kinds of array, numerically-indexed and
       associative.  Perl associative arrays are called "hashes".
       Awk arrays are usually translated to hashes, but if you
       happen to know that the index is always going to be
       iteration over an array is NOT.  You might need to modify
       any loop that iterates over such an array.

       default value of OFMT.

       Near the top of the line loop will be the split operation
       that is implicit in the awk script.  There are times when
       you can move this down past some conditionals that test

       For aesthetic reasons you may wish to change the array
       to change all array subscripts AND all substr() and
       index() operations to match.

       Cute comments that say "# Here is a workaround because awk
       is dumb" are passed through unmodified.

       Awk scripts are often embedded in a shell script that
       pipes stuff into and out of awk.  Often the shell script
       wrapper can be incorporated into the perl script, since
       other things that awk can't do by itself.

       Scripts that refer to the special variables RSTART and
       RLENGTH can often be simplified by referring to the
       scope of the pattern match that sets them.

       The produced perl script may have subroutines defined to
       deal with awk's semantics regarding getline and print.
       Since a2p usually picks correctness over efficiency.  it
       is almost always possible to rewrite such code to be more
       efficient by discarding the semantic sugar.

       For efficiency, you may wish to remove the keyword from
       any return statement that is the last statement executed
       in a subroutine.  A2p catches the most common case, but
       doesn't analyze embedded blocks for subtler cases.

       won't find it.

       A2p uses no environment variables.

       Larry Wall <larry@wall.org>

        perl   The perl compiler/interpreter

        s2p    sed to perl translator

       It would be possible to emulate awk's behavior in
       selecting string versus numeric operations at run time by
       inspection of the operands, but it would be gross and
       inefficient.  Besides, a2p almost always guesses right.

       Storage for the awk syntax tree is currently static, and
       can run out.

29/Jul/1998            perl 5.005, patch 03                     1