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cmp takes skip and length


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#1 deomsh


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Posted 3 weeks ago

With help of the famous experimental method I found grub4dos internal function cmp can be used for more than blocklists, comparison of whole-sectors or two files with identical filesize.


If comparing a file and a bloklist or two blocklists, cmp seems to take skip and filesize in the same way as known for cat. As far as I know this is undocumented. Please correct me if I am wrong :ph34r:

See first print-screen for an example:


CMP with skip and length I.png


BTW as can be seen even cmp --hex FILE is willing to take skip, but the value of %@retval% seems to have the meaning that cat --hex succeeded to give output on screen - nothing more


As long as filesize is same, normal cmp with skip seems to give correct results. See second print-screen for comparison of a file and a blocklist:


CMP with skip and length II.png


Same for two blocklists, see last print-screen:


CMP with skip & length III.png


BTW as can bee seen even dd seems to take copy-size after the blocklist comma - bs and count does not seem necessary in this case


Used grub4dos version: 2022-12-22

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