codice:
<<EOF A line-oriented form of quoting is based on the shell
"here-document" syntax. Following a "<<" you specify a string
to terminate the quoted material, and all lines following the
current line down to the terminating string are the value of
the item. The terminating string may be either an identifier
(a word), or some quoted text. If quoted, the type of quotes
you use determines the treatment of the text, just as in regu-
lar quoting. An unquoted identifier works like double quotes.
There must be no space between the "<<" and the identifier,
unless the identifier is quoted. (If you put a space it will
be treated as a null identifier, which is valid, and matches
the first empty line.) The terminating string must appear by
itself (unquoted and with no surrounding whitespace) on the
terminating line.
print <<EOF;
The price is $Price.
EOF
print << "EOF"; # same as above
The price is $Price.
EOF
print << ‘EOC‘; # execute commands
echo hi there
echo lo there
EOC
print <<"foo", <<"bar"; # you can stack them
I said foo.
foo
I said bar.
bar
myfunc(<< "THIS", 23, <<’THAT’);
Here’s a line
or two.
THIS
and here’s another.
THAT
Just don’t forget that you have to put a semicolon on the end
to finish the statement, as Perl doesn’t know you’re not going
to try to do this:
print <<ABC
179231
ABC
+ 20;
If you want your here-docs to be indented with the rest of the
code, you’ll need to remove leading whitespace from each line
manually:
($quote = <<’FINIS’) =~ s/^\s+//gm;
The Road goes ever on and on,
down from the door where it began.
FINIS
If you use a here-doc within a delimited construct, such as in
"s///eg", the quoted material must come on the lines following
the final delimiter. So instead of
s/this/<<E . ’that’
the other
E
. ’more ’/eg;
you have to write
s/this/<<E . ’that’
. ’more ’/eg;
the other
E
If the terminating identifier is on the last line of the pro-
gram, you must be sure there is a newline after it; otherwise,
Perl will give the warning Can’t find string terminator "END"
anywhere before EOF....
Additionally, the quoting rules for the identifier are not
related to Perl’s quoting rules -- "q()", "qq()", and the like
are not supported in place of '' and "", and the only interpo-
lation is for backslashing the quoting character:
print << "abc\"def";
testing...
abc"def
Finally, quoted strings cannot span multiple lines. The gen-
eral rule is that the identifier must be a string literal.
Stick with that, and you should be safe.
Rispondi quotando