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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 }}} |
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