Re^3: skip junk lines in csv before header

The do is actually redundant, he can use a basic block for localizing the $INPUT_RECORD_SEPARATOR aka $/

use v5.12;
use warnings;
use Data::Dump qw/pp dd/;

say pp $/;                              # show default

say my $x =
  "HEADER\n" x 3 .
  "fieldname: BLA BLA\n" .
  join $/, 1..5;

open my $fh, '<', \$x;

# ignore anything prior to "fieldname"
{ local $/ = "fieldname:"; <$fh> };

say pp $/;                              # back to default

say "-" x 10;

say "fieldname:" . <$fh>;               # till end of line
[download]

"\n" HEADER HEADER HEADER fieldname: BLA BLA 1 2 3 4 5 "\n" ---------- fieldname: BLA BLA
[download]

Cheers Rolf
_{(addicted to the Perl Programming Language :)

Wikisyntax for the Monastery}

Comment on Re^3: skip junk lines in csv before header Select or Download Code

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Re^4: skip junk lines in csv before header by AnomalousMonk (Archbishop) on Jul 28, 2022 at 15:28 UTC
It occurs to me that there might be a use for a `do`-block. If no `'fieldname'` string is present in the file, `<$fh>` will read to the end of the file. This will be a valid read. If the data of the read is returned as from a `do`-block, it can be tested to determine if a header was actually present. (The data could be returned from a "naked" block, but using a `do`-block is neater IMHO.) Win8 Strawberry 5.8.9.5 (32) Thu 07/28/2022 11:22:44 C:\@Work\Perl\monks >perl use strict; use warnings; use Data::Dump qw(dd); use constant FIELDNAME => 'fieldname'; open my $fh, '<', \<<END or die; no valid header present value1,value2 END my $got_header = do { local $/ = FIELDNAME; <$fh>; }; dd $got_header; # for debug $got_header =~ m{ \Q${ \FIELDNAME }\E \z }xms or die "no header"; my $header_line = FIELDNAME . <$fh>; # complete the line # and so on... ^Z "no valid header present\nvalue1,value2\n" no header at - line 16, <$fh> line 1. [download] Give a man a fish: `<%-{-{-{-<`	[reply] [d/l] [select]
Re^5: skip junk lines in csv before header by LanX (Saint) on Jul 28, 2022 at 15:45 UTC
well, yes if you want to capture the first 'readline', a do block is better, because of all the scoping. Cheers Rolf _{(addicted to the Perl Programming Language :) Wikisyntax for the Monastery}	[reply]