Thanks Travis, I'll give your code a shot, but every time I use backticks my
computer crashes.
Thanks to John and Tom for suggesting "do" and "eval". I read up on those.
I don't understand them entirely, but I experimented. They seem to
accomplish about the same thing. I wrote two one-line programs: print
eval(system('perl -c nextprogramtoexecute.pl')); and
print do {system('perl -c nextprogramtoexecute.pl')};
They both give the same results. When nextprogramtoexecute.pl has a
syntax error I see the error message (saying it's in line 3 near such and such
or whatever) and the next line has the number 65280. (Which is 255 x 2 to the
eighth I noticed.) And when nextprogramtoexecute.pl has sound syntax, I see
the message "nextprogramtoexecute.pl syntax OK", and the next line has the
number 0. Getting a zero, or some number, of course, is all the basis I need.
What I'm inclined to do then, is write something like
unless (eval(system('perl -c nextprogramtoexecute.pl')))
{require (nextprogramtoexecute.pl)}
meaning unless there's a syntax error, run the program (exactly what
I've been going for).
It seems like I can do that. Have I got it? Since I don't entirely
understand 'do' and 'eval' I'm afraid I might be overgeneralizing from these
examples. In other words, what if another syntax error also returned zero?
(Or is it possible some syntax OK message could return a number other than
zero?) In that case I wouldn't be getting what I need. (I don't need to
distinguish between different syntax errors, just know whether or not there is
one.)
Fred Kittelmann
Travis Thornhill <[EMAIL PROTECTED]> wrote:Actually if the syntax is good the
output will contain one line. If there are errors there will be multiple
lines. This would work better:
my $progname = "whatever.pl";
my @output = `perl -c $progname`;
my $syntax_ok = 0;
foreach my $line ( @output ) {
if ( $line =~ /$progname syntax OK/ ) {
$syntax_ok = 1;
last;
}
}
Travis Thornhill wrote:
Would something like this (with backticks) work?
It's probably not as robust as using 'do BLOCK' but it might
work.
#untested
my $progname = "whatever.pl";
my $output = `perl -c $progname`;
if ( $output =~ /$progname syntax OK/ ) {
# It's good
} else {
# It's bad
}
hOURS wrote:
Hi all,
I've written a PERL program that runs other PERL programs (through 'require'
statements and what not). It worked fine for a couple tasks I had in mind, but
there's an obstacle ahead in the next thing I want to use it for. The programs
it will execute may (or may not) have syntax errors. Asking it to 'require' a
program with a syntax error will cause the main program to quit and print out
the appropriate error message for that. I don't want that. I want it to keep
going.
Recently I've posted questions here about compiling. My thinking was that if
my main program were running machine language programs instead, I wouldn't get
those syntax errors. (The programs might still be junk, and might give
peculiar results, but that's ok.) I haven't figured that out yet, but I
havent given up on it either.
However my uncle suggested another possibility, avoiding any need to compile;
that I check for syntax errors first - in which case I can simply go on to the
next program, thereby avoiding a shutdown of the main program. This sounded
nice but seemed hopeless in practicality (there are so many possible syntax
errors). But then it occurred to me that PERL already checks for syntax
errors. It recognizes them of course, but there's also the -c option. I
thought I could put a line in the main program like
system('perl -c nextprogramtoexecute.pl');
and check to see if that gives me a syntax OK message or not. But I can't
figure out how to get a hold of the message. I figured it would be in STDOUT,
but I can't figure out how to make use of that. I have a PERL textbook in
front of me, but it says precious little about STDOUT. I've tried capturing
this in a variable with backticks, qx//, and the open function with a vertical
bar. All of those shut down my computer, saying I performed an illegal
operation. (Which in itself is another problem. I mean it's one thing to just
not work...)
So, many thanks in advance to anyone who can tell me how to use STDOUT for
this. Or if you have another way to read that message before the program
quits, or another way to test for syntax errors... that's cool too. But I
suspect STDOUT is going to be the best thing.
Fred Kittelmann
P.S. I'm not using UNIX, if that matters.
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