Beefy Boxes and Bandwidth Generously Provided by pair Networks
Just another Perl shrine
 
PerlMonks  

Comment on

( #3333=superdoc: print w/ replies, xml ) Need Help??

No, you can use truncate and seek and if you put them together in a subroutine you only have to make one call each time to empty your file ready for the next print statement. Note that /usr/bin/hexdump run on an empty file produces no output.

$ perl -Mstrict -Mwarnings -e ' > sub truncZero > { > my $fh = shift; > truncate $fh, 0 or die $!; > seek $fh, 0, 0 or die $!; > } > > open my $fh, q{>}, q{rubbish} or die $!; > > print $fh qq{Mary had a little lamb\n}; > print qx{/usr/bin/hexdump -vC rubbish}, qq{-----\n}; > > truncZero( $fh ); > print qx{/usr/bin/hexdump -vC rubbish}, qq{-----\n}; > > print $fh qq{The boy stood on the burning deck\n}; > print qx{/usr/bin/hexdump -vC rubbish}, qq{-----\n}; > > truncZero( $fh ); > print qx{/usr/bin/hexdump -vC rubbish}, qq{-----\n}; > > print $fh qq{I met a traveller from an antique land\n}; > print qx{/usr/bin/hexdump -vC rubbish}, qq{-----\n}; > > close $fh or die $!;' 00000000 4d 61 72 79 20 68 61 64 20 61 20 6c 69 74 74 6c |Mary had +a littl| 00000010 65 20 6c 61 6d 62 0a |e lamb.| 00000017 ----- ----- 00000000 54 68 65 20 62 6f 79 20 73 74 6f 6f 64 20 6f 6e |The boy s +tood on| 00000010 20 74 68 65 20 62 75 72 6e 69 6e 67 20 64 65 63 | the burn +ing dec| 00000020 6b 0a |k.| 00000022 ----- ----- 00000000 49 20 6d 65 74 20 61 20 74 72 61 76 65 6c 6c 65 |I met a t +ravelle| 00000010 72 20 66 72 6f 6d 20 61 6e 20 61 6e 74 69 71 75 |r from an + antiqu| 00000020 65 20 6c 61 6e 64 0a |e land.| 00000027 ----- $ cat rubbish I met a traveller from an antique land $

I hope this is helpful.

Cheers,

JohnGG


In reply to Re^5: Empty File Contents before writing by johngg
in thread Empty File Contnts before writing by gautamparimoo

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post; it's "PerlMonks-approved HTML":



  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • Outside of code tags, you may need to use entities for some characters:
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.
  • Log In?
    Username:
    Password:

    What's my password?
    Create A New User
    Chatterbox?
    and the web crawler heard nothing...

    How do I use this? | Other CB clients
    Other Users?
    Others contemplating the Monastery: (4)
    As of 2014-09-23 04:06 GMT
    Sections?
    Information?
    Find Nodes?
    Leftovers?
      Voting Booth?

      How do you remember the number of days in each month?











      Results (210 votes), past polls