jay28lee
asked on
How do I replace a block of text using regular expressions in Perl?
I have the following subroutine reading the content of a text file template
The template contains block of content I would like to replace, from <!--tmpl_start--> to <!--tmpl_end--> where anything can possibly go in between.
It would be easy to use a foreach loop if they are on the same line.
How do I implement this if they're on different lines?
sub readfile {
open(INFILE,"$_[0]");
flock(INFILE,2);
my @content=<INFILE>;
flock(INFILE,8);
close(INFILE);
return @content;
}The template contains block of content I would like to replace, from <!--tmpl_start--> to <!--tmpl_end--> where anything can possibly go in between.
It would be easy to use a foreach loop if they are on the same line.
How do I implement this if they're on different lines?
ASKER CERTIFIED SOLUTION
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ASKER
another thing, once $content variable is returned, how can i re-assign it to an array variable?
there are other tasks i need to manipulate using the foreach loop and $_ line by line.
there are other tasks i need to manipulate using the foreach loop and $_ line by line.
SOLUTION
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perldoc perlvar
...
$/ The input record separator, newline by default. This
influences Perl's idea of what a "line" is. Works like awk's
RS variable, including treating empty lines as a terminator if
set to the null string. (An empty line cannot contain any
spaces or tabs.) You may set it to a multi-character string to
match a multi-character terminator, or to "undef" to read
through the end of file. Setting it to "\n\n" means something
slightly different than setting to "", if the file contains
consecutive empty lines. Setting to "" will treat two or more
consecutive empty lines as a single empty line. Setting to
"\n\n" will blindly assume that the next input character
belongs to the next paragraph, even if it's a newline.
(Mnemonic: / delimits line boundaries when quoting poetry.)
local $/; # enable "slurp" mode
local $_ = <FH>; # whole file now here
s/\n[ \t]+/ /g;
Remember: the value of $/ is a string, not a regex. awk has to
be better for something. :-)
Setting $/ to a reference to an integer, scalar containing an
integer, or scalar that's convertible to an integer will
attempt to read records instead of lines, with the maximum
record size being the referenced integer. So this:
local $/ = \32768; # or \"32768", or \$var_containing_32768
open my $fh, $myfile or die $!;
local $_ = <$fh>;
will read a record of no more than 32768 bytes from FILE. If
you're not reading from a record-oriented file (or your OS
doesn't have record-oriented files), then you'll likely get a
full chunk of data with every read. If a record is larger than
...
$/ The input record separator, newline by default. This
influences Perl's idea of what a "line" is. Works like awk's
RS variable, including treating empty lines as a terminator if
set to the null string. (An empty line cannot contain any
spaces or tabs.) You may set it to a multi-character string to
match a multi-character terminator, or to "undef" to read
through the end of file. Setting it to "\n\n" means something
slightly different than setting to "", if the file contains
consecutive empty lines. Setting to "" will treat two or more
consecutive empty lines as a single empty line. Setting to
"\n\n" will blindly assume that the next input character
belongs to the next paragraph, even if it's a newline.
(Mnemonic: / delimits line boundaries when quoting poetry.)
local $/; # enable "slurp" mode
local $_ = <FH>; # whole file now here
s/\n[ \t]+/ /g;
Remember: the value of $/ is a string, not a regex. awk has to
be better for something. :-)
Setting $/ to a reference to an integer, scalar containing an
integer, or scalar that's convertible to an integer will
attempt to read records instead of lines, with the maximum
record size being the referenced integer. So this:
local $/ = \32768; # or \"32768", or \$var_containing_32768
open my $fh, $myfile or die $!;
local $_ = <$fh>;
will read a record of no more than 32768 bytes from FILE. If
you're not reading from a record-oriented file (or your OS
doesn't have record-oriented files), then you'll likely get a
full chunk of data with every read. If a record is larger than
ASKER
with the modified: return split/^/m,$content;
can i now use the following?
@template = &readfile("$path_to_file")
also, what does the line: open(INFILE,"$_[0]") or die "$_[0] $!";
what does this condition die "$_[0] $!" evaluate?
thanks
can i now use the following?
@template = &readfile("$path_to_file")
also, what does the line: open(INFILE,"$_[0]") or die "$_[0] $!";
what does this condition die "$_[0] $!" evaluate?
thanks
perldoc perlvar
...
$OS_ERROR
$ERRNO
$! If used numerically, yields the current value of the C "errno"
variable, or in other words, if a system or library call fails,
it sets this variable. This means that the value of $! is
meaningful only immediately after a failure:
if (open(FH, $filename)) {
# Here $! is meaningless.
...
} else {
# ONLY here is $! meaningful.
...
# Already here $! might be meaningless.
}
# Since here we might have either success or failure,
# here $! is meaningless.
In the above meaningless stands for anything: zero, non-zero,
"undef". A successful system or library call does not set the
variable to zero.
If used as a string, yields the corresponding system error
string. You can assign a number to $! to set errno if, for
instance, you want "$!" to return the string for error n, or
you want to set the exit value for the die() operator.
(Mnemonic: What just went bang?)
Also see "Error Indicators".
...
$OS_ERROR
$ERRNO
$! If used numerically, yields the current value of the C "errno"
variable, or in other words, if a system or library call fails,
it sets this variable. This means that the value of $! is
meaningful only immediately after a failure:
if (open(FH, $filename)) {
# Here $! is meaningless.
...
} else {
# ONLY here is $! meaningful.
...
# Already here $! might be meaningless.
}
# Since here we might have either success or failure,
# here $! is meaningless.
In the above meaningless stands for anything: zero, non-zero,
"undef". A successful system or library call does not set the
variable to zero.
If used as a string, yields the corresponding system error
string. You can assign a number to $! to set errno if, for
instance, you want "$!" to return the string for error n, or
you want to set the exit value for the die() operator.
(Mnemonic: What just went bang?)
Also see "Error Indicators".
ASKER
everything works perfect.
ASKER
local $/;