Diff for "BashFAQ/019"

Differences between revisions 1 and 107 (spanning 106 versions)

Good day! Even though you've still got another op in front of you, I know you'll be up and rarin' to go for Brands because anyone that has achieved what you have since your accident, will make sure that it happens kitchen whens the next production?! http://smokeydevo.blogspirit.com/tag/chicken syrup, Very interesting.

-  ⇤ ← Revision 1 as of 2007-05-02 23:05:11 → 
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+   ← Revision 107 as of 2008-12-03 06:38:03 → ⇥
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  Editor: 91
  Comment: Good day! Even though you've still got another op in front of you, I know you'll be up and rarin' to go for Brands because anyone that has achieved what you have since your accident, will make sure th
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-[[Anchor(faq19)]]
== How can I split a file into line ranges, e.g. lines 1-10, 11-20, 21-30? ==
Some Unix systems provide the {{{split}}} utility for this purpose:

{{{
    split --lines 10 --numeric-suffixes input.txt output-
}}}

For more flexibility you can use {{{sed}}}.  The {{{sed}}} command can print e.g. the line number range 1-10:
{{{
    sed -n '1,10p'
}}}

This stops {{{sed}}} from printing each line ({{{-n}}}). Instead it only processes the lines in the range 1-10 ("1,10"), and prints them ("p"). {{{sed}}} still reads the input until the end, although we are only interested in lines 1 though 10. We can speed this up by making {{{sed}}} terminate immediately after printing line 10:

{{{
    sed -n -e '1,10p' -e '10q'
}}}

Now the command will quit after reading line 10 ("10q"). The {{{-e}}} arguments indicate a script (instead of a file name). The same can be written a little shorter:

{{{
    sed -n '1,10p;10q'
}}}

We can now use this to print an arbitrary range of a file (specified by line number):

{{{
file=/etc/passwd
range=10
firstline=1
maxlines=$(wc -l < "$file") # count number of lines
while (($firstline < $maxlines))
do
    ((lastline=$firstline+$range+1))
    sed -n -e "$firstline,${lastline}p" -e "${lastline}q" "$file"
    ((firstline=$firstline+$range+1))
done
}}}

This example uses ["BASH"] and KornShell ArithmeticExpressions, which older [wiki:Self:BourneShell Bourne shells] do not have. In that case the following example should be used instead:

{{{
file=/etc/passwd
range=10
firstline=1
maxlines=`wc -l < "$file"` # count line numbers
while [ $firstline -le $maxlines ]
do
    lastline=`expr $firstline + $range + 1`
    sed -n -e "$firstline,${lastline}p" -e "${lastline}q" "$file"
    firstline=`expr $lastline + 1`
done
}}}
+Good day! Even though you've still got another op in front of you, I know you'll be up and rarin' to go for Brands because anyone that has achieved what you have since your accident, will make sure that it happens kitchen whens the next production?! http://smokeydevo.blogspirit.com/tag/chicken syrup,  Very interesting.