Print every Nth line
my_verbose_command | every 100
will print every 100th line of output.
Specifically, it will print lines 100, 200, 300, etc
If you use a negative argument it will print the *first* of a block,
my_verbose_command | every -100
It will print lines 1, 101, 201, 301, etc
The function wraps up this useful sed snippet:
... | sed -n '0~100p'
don't print anything by default
sed -n
starting at line 0, then every hundred lines ( ~100 ) print.
'0~100p'
There's also some bash magic to test if the number is negative:
we want character 0, length 1, of variable N.
${N:0:1}
If it *is* negative, strip off the first character ${N:1} is character 1 onwards (second actual character).
$ seq 100 | every 10 10 20 30 40 50 60 70 80 90 100 $ seq 100 | every -10 1 11 21 31 41 51 61 71 81 91
1 Alternatives + Submit Alt
-
Thanks to knoppix5 for the idea :-) Print selected lines from a file or the output of a command. Usage:
every NTH MAX [FILE]Print every NTH line (from the first MAX lines) of FILE. If FILE is omitted, stdin is used. The command simply passes the input to a sed script:sed -n -e "${2}q" -e "0~${1}p" ${3:-/dev/stdin}print no outputsed -nquit after this many lines (controlled by the second parameter)-e "${2}q"print every NTH line (controlled by the first parameter)-e "0~${1}p"take input from $3 (if it exists) otherwise use /dev/stdin{3:-/dev/stdin}Show Sample Output2function every() { sed -n -e "${2}q" -e "0~${1}p" ${3:-/dev/stdin}; }
What do you think?
Any thoughts on this command? Does it work on your machine? Can you do the same thing with only 14 characters?
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every() { c=$1;for a in $(seq 1 $c $2);do head -$a $3|tail -1;done }every 20 500 file.txt # prints every 20-th from 1 to 500 lines of file file.txtHowever, could not find an easy way to apply this to output of verbose commands. Maybe eats resources too.awk 'NR%100==0' filename.txtsed -n '0~10p' FILENAMETo match my command, you need: every() { N=$1; S=1; [ "${N:0:1}" = '-' ] && N="${N:1}" || S=0; awk "NR%$N==$S"; }