i just want move the filesystem pointer from the actual "begginning of file" to a "new beginning of file"...

No filesystem (AFAIK) provides that facility.

In theory, it could be done (after a fashion) using low-level IO primitives, but only to the nearest block boundary -- which might be modulus 512, 4096 or some other power of 2 depending upon the device the file is located on -- which isn't very useful.

It is possible to truncate the end of a file on most file systems; and again in theory, it might be somewhat quicker to copy the rest of the file over the removed portion in situ, then truncate the end. But it is easy to get this wrong and there is no guarentee it will be quicker on any given device or day.

With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority". The enemy of (IT) success is complexity.
In the absence of evidence, opinion is indistinguishable from prejudice. Suck that fhit

In reply to Re^3: Fastest way of changing the beginning of a txt file.. -- oneliner by BrowserUk
in thread Fastest way of changing the beginning of a txt file.. by pedrete

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!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • 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, details, 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, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            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.