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  • Re: [gentoo-user] wiki page(kernel/upgrade) command confusion: 'cat' an

    From Frank Steinmetzger@21:1/5 to All on Fri Jan 14 13:20:02 2022
    Am Fri, Jan 14, 2022 at 10:05:54AM +0000 schrieb russian sky:
    the sentence is just as follows:

    diff <(cat .config | sort) <(cat .config.old | sort) | awk '/^>.*(=|Linux)/ { $1=""; print }'

    without inserting the 'cat' and '*'(the part of awk),It seems like, the result of the command is the same as before.


    Does the existence of the aboving 'cat'

    This, in my opinion, is a case of “useless use of cat”.
    `cat somefile | sort` can be replaced by “sort file”.

    and '*' (the part of awk)

    I don’t quite follow. Do you mean the “.*”, so you replace .* with .?

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  • From Frank Steinmetzger@21:1/5 to All on Fri Jan 14 16:00:01 2022
    Am Fri, Jan 14, 2022 at 02:38:22PM +0000 schrieb russian sky:

    I don’t quite follow. Do you mean the “.*”, so you replace .* with .?
    Yes. Based on the explanation of '*' in the gawk manual, it's
    used to match zero/one/more times repeating of the preceding character which in turn doesn't match the default
    diff printing mode( >for removing, <for adding).

    Why would it not match? . means “any character”.

    It's not necessary to add '*' to '/^>.*(=|Linux)/'.

    I think it is.

    “.*” basically means “any string of any length, including 0. “.” means
    “exactly one character”.

    So your original pattern will match '>somestuff=', '> a=', and even
    Linux'. But without the *, it will only match if there is that one
    character between > and = or Linux. Acutally, diff adds a space after the >,
    so your expression will only match lines starting with '> =' or with '>
    Linux'.

    I’d actually replace gawk with sed, because the output of your gawk command leaves the space in. If an example output for diff is:
    6,7c6
    < CONFIG_CC_IS_GCC=y
    < CONFIG_GCC_VERSION=110100
    ---
    CONFIG_CC_IS_GCC=n

    Then your line returns:
    CONFIG_CC_IS_GCC=n

    If you use `sed -n 's/^> //p'` instead, the output will become: CONFIG_CC_IS_GCC=n

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  • From russian sky@21:1/5 to All on Fri Jan 14 15:40:01 2022
    This, in my opinion, is a case of �useless use of cat�.
    `cat somefile | sort` can be replaced by �sort file�.
    Agree with that, i will attempt to add an replacing
    adivce to the talking page of the kernel/upgrade wiki
    page.

    I don�t quite follow. Do you mean the �.*�, so you replace .* with .?
    Yes. Based on the explanation of '*' in the gawk manual, it's
    used to match zero/one/more times repeating of the preceding character which in turn doesn't match the default
    diff printing mode( >for removing, <for adding). It's not
    necessary to add '*' to '/^>.*(=|Linux)/'.

    <html>
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    <div class="PlainText">&gt; This, in my opinion, is a case of �useless use of cat�.<br>
    &gt; `cat somefile | sort` can be replaced by �sort file�.<br>
    Agree with that, i will attempt to add an replacing</div>
    <div class="PlainText">adivce&nbsp; to the talking page of the kernel/upgrade wiki</div>
    <div class="PlainText">page.</div>
    <div class="PlainText"><br>
    </div>
    <div class="PlainText">&gt; I don�t quite follow. Do you mean the �.*�, so you replace .* with .?<br>
    Yes. Based on the explanation of '*' in the gawk manual, it's</div>
    <div class="PlainText">used to match zero/one/more times repeating of the preceding character which in turn doesn't match the default</div>
    <div class="PlainText">diff printing mode( &gt;for removing, &lt;for adding). It's not <br>
    </div>
    <div class="PlainText">necessary to add '*' to '/^&gt;.*(=|Linux)/'.<br>
    </div>
    <div>
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