This is a quick method of pulling the segment terminator and element separator out of an ANSI X.12 EDI file (ISA header only). It follows these rules:

  • Linefeed can be a either a segment terminator or a blocking character, but not both.
  • The ISA segment must start at the beginning of the file.
  • Underscore is not a valid delimiter (for the convenience of \w and \W, and my laziness) 
    • #!/usr/bin/perl -w
use strict;

sub isa_fail { die "Problem parsing ISA segment : " . shift; }

sub get_delimiters  {
    local $/ = \4;
    my $chunk = <>;
    isa_fail "ISA can't start with $chunk" unless my($ed) = $chunk =~ 
+/^ISA([^\w\n])$/;
    $/ = \101;
    my $num_linefeeds = scalar @{[<> =~ /\n/g]};
    $/ = \($num_linefeeds + 1);
    my $st = substr(<>, -1);
    isa_fail 'Linefeeds as both delimiter and blocking' if $st eq "\n"
+ && $num_linefeeds;
    return ($ed, $st) if $st =~ /\W/;
    isa_fail "Segment terminator can't be $st";
}

my ($elem_sep, $seg_term) = &get_delimiters;
$seg_term = 'line feed' if $seg_term eq "\n";
print "Element separator  = $elem_sep\n";
print "Segment terminator = $seg_term\n";

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    In reply to Getting an ANSI X.12 file's delimiters by delirium

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