perl: read in files in several ways

#!/opt/VRTSperl/bin/perl -w use strict; my $file = shift; print "==================read file line by line/n"; read_file("$/", $file); print "==================read the whole file at one time/n"; read_file(undef, $file); print "==================read file paragraph by paragraph/n"; &read_file("", $file); print "==================read file in unix fortunes/n"; &read_file("/n%/n", $file); sub read_file { my $loop = 1; my $fh; local $/ = $_[0]; my $f = $_[1]; open($fh, "<", $f) or die $!; while (<$fh>) { print "loop: $loop/n"; print $_; ++$loop; } close($fh); }

 

$/ is a global var-- input record separator. when it is modified, it will take effect in the left part of programme, we can localize it to the current block.

 

{

     local $/ = "";

     ......

}

 

NOTE: local can only change special  vars in the current block, we can not use if to define a new var.

 

1. By default, read in file line by line;

2. $/ = undef, read in the whole file at once;

3. $/ = "", read in paragraph by paragraph.

4. $/ = "/n%/n", read in unix fortunes.