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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): {{{ # POSIX shell file=/etc/passwd range=10 cur=1 last=$(wc -l < "$file") # count number of lines chunk=1 while [ $cur -lt $last ] do endofchunk=$(($cur + $range - 1)) sed -n -e "$cur,${endofchunk}p" -e "${endofchunk}q" "$file" > chunk.$(printf %04d $chunk) chunk=$(($chunk + 1)) cur=$(($cur + $range)) done }}} The previous example uses POSIX [:ArithmeticExpression:arithmetic], which older [:BourneShell:Bourne shells] do not have. In that case the following example should be used instead: {{{ # legacy Bourne shell; assume no printf either file=/etc/passwd range=10 cur=1 last=`wc -l < "$file"` # count number of lines chunk=1 while test $cur -lt $last do endofchunk=`expr $cur + $range - 1` sed -n -e "$cur,${endofchunk}p" -e "${endofchunk}q" "$file" > chunk.$chunk chunk=`expr $chunk + 1` cur=`expr $cur + $range` done }}} |
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