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8.23. Pretending a String Is a File
8.23.1. Problem
You have data in string, but would like
to treat it as a file. For example, you have a subroutine that
expects a filehandle as an argument, but you would like that
subroutine to work directly on the data in your string instead.
Additionally, you don''t want to write the data to a temporary file.
8.23.2. Solution
Use the scalar I/O in Perl v5.8:
open($fh, "+<", \$string);
# read and write contents of $string
8.23.3. Discussion
Perl''s I/O
layers include support for input and output from a scalar. When you
read a record with <$fh>, you are reading
the next line from $string. When you write a
record with print, you change
$string. You can pass $fh to a
function that expects a filehandle, and that subroutine need never
know that it''s really working with data in a string.Perl respects the various access modes in open for
strings, so you can specify that the strings be opened as read-only,
with truncation, in append mode, and so on:
open($fh, "<", \$string); # read only
open($fh, ">", \$string); # write only, discard original contents
open($fh, "+>", \$string); # read and write, discard original contents
open($fh, "+<", \$string); # read and write, preserve original contents
These handles behave in all respects like regular filehandles, so all
I/O functions work, such as seek,
truncate, sysread, and friends.
8.23.4. See Also
The open function in
perlfunc(1) and in Chapter 29 of
Programming Perl; Recipe 8.12 and Recipe 8.19
