Diff for "BashFAQ/019"

Differences between revisions 1 and 141 (spanning 140 versions)

Good morning. Much love Hi there to the most loving couple and Jackie, Happy Anniversary and may you both be spared to see many many more !!!!!!! You have proved that people can come through personal tragedy and get on with their lives, your story will always be with everyone who was at Goodwood that day and having just got back from this years event it is humbling to read your story, good luck to you both, Congratulations on getting this far chicken What a strange place here. http://salinasii.interfree.it/recipecd6.html salad, Thanks for your project.

-  ⇤ ← Revision 1 as of 2007-05-02 23:05:11 → 
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  Editor: redondos
  Comment:
+   ← Revision 141 as of 2009-01-10 23:54:39 → ⇥
  Size: 561
  Editor: cable73
  Comment: -9
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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 morning. Much love Hi there to the most loving couple and Jackie, Happy Anniversary and may you both be spared to see many many more !!!!!!! You have proved that people can come through personal tragedy and get on with their lives, your story will always be with everyone who was at Goodwood that day and having just got back from this years event it is humbling to read your story, good luck to you both, Congratulations on getting this far chicken What a strange place here. http://salinasii.interfree.it/recipecd6.html salad,  Thanks for your project.