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Diffstat (limited to 'gnu/usr.bin/perl/x2p/a2p.1')
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diff --git a/gnu/usr.bin/perl/x2p/a2p.1 b/gnu/usr.bin/perl/x2p/a2p.1 new file mode 100644 index 0000000..58d8c07 --- /dev/null +++ b/gnu/usr.bin/perl/x2p/a2p.1 @@ -0,0 +1,199 @@ +.rn '' }` +''' $Header: /home/cvs/386BSD/ports/lang/perl/x2p/a2p.man,v 1.1.1.1 1993/08/23 21:30:10 nate Exp $ +''' +''' $Log: a2p.man,v $ +.\" Revision 1.1.1.1 1993/08/23 21:30:10 nate +.\" PERL! +.\" +''' Revision 4.0 91/03/20 01:57:11 lwall +''' 4.0 baseline. +''' +''' Revision 3.0 89/10/18 15:34:22 lwall +''' 3.0 baseline +''' +''' Revision 2.0.1.1 88/07/11 23:16:25 root +''' patch2: changes related to 1985 awk +''' +''' Revision 2.0 88/06/05 00:15:36 root +''' Baseline version 2.0. +''' +''' +.de Sh +.br +.ne 5 +.PP +\fB\\$1\fR +.PP +.. +.de Sp +.if t .sp .5v +.if n .sp +.. +.de Ip +.br +.ie \\n.$>=3 .ne \\$3 +.el .ne 3 +.IP "\\$1" \\$2 +.. +''' +''' Set up \*(-- to give an unbreakable dash; +''' string Tr holds user defined translation string. +''' Bell System Logo is used as a dummy character. +''' +.tr \(*W-|\(bv\*(Tr +.ie n \{\ +.ds -- \(*W- +.if (\n(.H=4u)&(1m=24u) .ds -- \(*W\h'-12u'\(*W\h'-12u'-\" diablo 10 pitch +.if (\n(.H=4u)&(1m=20u) .ds -- \(*W\h'-12u'\(*W\h'-8u'-\" diablo 12 pitch +.ds L" "" +.ds R" "" +.ds L' ' +.ds R' ' +'br\} +.el\{\ +.ds -- \(em\| +.tr \*(Tr +.ds L" `` +.ds R" '' +.ds L' ` +.ds R' ' +'br\} +.TH A2P 1 LOCAL +.SH NAME +a2p - Awk to Perl translator +.SH SYNOPSIS +.B a2p [options] filename +.SH DESCRIPTION +.I A2p +takes an awk script specified on the command line (or from standard input) +and produces a comparable +.I perl +script on the standard output. +.Sh "Options" +Options include: +.TP 5 +.B \-D<number> +sets debugging flags. +.TP 5 +.B \-F<character> +tells a2p that this awk script is always invoked with this -F switch. +.TP 5 +.B \-n<fieldlist> +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: +.sp + a2p -7 -nlogin.password.uid.gid.gcos.shell.home +.sp +Any delimiter can be used to separate the field names. +.TP 5 +.B \-<number> +causes a2p to assume that input will always have that many fields. +.Sh "Considerations" +A2p cannot do as good a job translating as a human would, but it usually +does pretty well. +There are some areas where you may want to examine the perl script produced +and tweak it some. +Here are some of them, in no particular order. +.PP +There is an awk idiom of putting int() around a string 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 always going to be integer, so it leaves it in. +You may wish to remove it. +.PP +Perl differentiates numeric comparison from string comparison. +Awk has one operator for both that decides at run time which comparison +to do. +A2p does not try to do a 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 comment \*(L"#???\*(R". +You should go through and check them. +You might want to run at least once with the \-w switch to perl, which +will warn you if you use == where you should have used eq. +.PP +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 for...in, they won't be there in perl. +.PP +If a2p makes a split line that assigns to a list of variables that looks +like (Fld1, Fld2, Fld3...) you may want +to rerun a2p using the \-n 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. +.PP +The exit statement in awk doesn't necessarily exit; it goes to the END +block if there is one. +Awk scripts that 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. +.PP +Perl has two kinds of array, numerically-indexed and associative. +Awk arrays are usually translated to associative arrays, but if you happen +to know that the index is always going to be numeric you could change +the {...} to [...]. +Iteration over an associative array is done using the keys() function, but +iteration over a numeric array is NOT. +You might need to modify any loop that is iterating over the array in question. +.PP +Awk starts by assuming OFMT has the value %.6g. +Perl starts by assuming its equivalent, $#, to have the value %.20g. +You'll want to set $# explicitly if you use the default value of OFMT. +.PP +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 the entire record so that the split is not done as often. +.PP +For aesthetic reasons you may wish to change the array base $[ from 1 back +to perl's default of 0, but remember to change all array subscripts AND +all substr() and index() operations to match. +.PP +Cute comments that say "# Here is a workaround because awk is dumb" are passed +through unmodified. +.PP +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 +perl can start up pipes into and out of itself, and can do other things that +awk can't do by itself. +.PP +Scripts that refer to the special variables RSTART and RLENGTH can often +be simplified by referring to the variables $`, $& and $', as long as they +are within the scope of the pattern match that sets them. +.PP +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. +.PP +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. +.PP +ARGV[0] translates to $ARGV0, but ARGV[n] translates to $ARGV[$n]. +A loop that tries to iterate over ARGV[0] won't find it. +.SH ENVIRONMENT +A2p uses no environment variables. +.SH AUTHOR +Larry Wall <lwall@jpl-devvax.Jpl.Nasa.Gov> +.SH FILES +.SH SEE ALSO +perl The perl compiler/interpreter +.br +s2p sed to perl translator +.SH DIAGNOSTICS +.SH BUGS +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. +.PP +Storage for the awk syntax tree is currently static, and can run out. +.rn }` '' |
