How can I create a data file with one column in which there will be 1000 rows with zero values?
something like:
output:
0
0
0
0
0
.
.
.
You might use yes(1) for that (piped into head(1)...):
yes 0 | head -n 1000 > data_file_with_a_thousand_0s.txt
and if you need a million zeros, replace the 1000
with 1000000
PS. In the old days, head -1000
was enough since equivalent to head -n 1000
today.
Simply,
printf '0\n%.0s' {1..1000}
or using for
loop,
for i in {1..1000}; do echo "0"; done
using awk
,
awk 'BEGIN{for(c=0;c<1000;c++) print "0"}'
As @StéphaneChazelas pointed out, Using {1..1000}
requires zsh
or recent versions of bash
, yash
or ksh93
and also means storing the whole range in memory (possibly several times). You'll find it becomes a lot slower (if it doesn't crash for OOM) than using awk
or yes 0 | head ...
for large ranges like {1..10000000}
. Or in other words it doesn't scale well. Possible workaround would be to use
for ((i=0; i<=10000000;i++)); do echo 0; done
(ksh93
/zsh
/bash
) wouldn't have the memory issue but would still be orders of magnitude slower than a dedicated tool or real programming language approach.
printf
command might fail when 1000
gets replaced with 1000000
because the shell would fail execve(2) with E2BIG
Aug 5, 2016 at 5:45
{1..1000}
requires zsh
or recent versions of bash
, yash
or ksh93
and also means storing the whole range in memory (possibly several times). You'll find it becomes a lot slower (if it doesn't crash for OOM) than using awk
or yes|head
for large ranges like {1..10000000}
. Or in other words it doesn't scale well.
Aug 5, 2016 at 10:39
{x..y}
(zsh
, ksh93
, bash
and yash
) all have printf
builtin, so the E2BIG doesn't apply.
Aug 5, 2016 at 10:41
for ((i=0; i<=10000000;i++)); do echo 0; done
(ksh93
/zsh
/bash
) wouldn't have the memory issue but would still be orders of magnitude slower than a dedicated tool or real programming language approach.
Aug 5, 2016 at 10:58
perl -e 'print "0\n" x 1000' > file.txt
As @Stéphane Chazelas notes, this is fast for large numbers but can run into memory issues(use yes|head
approach in that case)
performance comparison, selected best out of 3 continuous runs
$ time perl -e 'print "0\n" x 100000000' > /dev/null
real 0m0.117s
$ time python -c 'import sys; sys.stdout.write("0\n" * 100000000)' > /dev/null
real 0m0.184s
$ time yes 0 | head -n 100000000 > /dev/null
real 0m0.979s
$ time awk 'BEGIN{for(c=0;c<100000000;c++) print "0"}' > /dev/null
real 0m12.933s
$ time seq 0 0 0 | head -n 100000000 > /dev/null
real 0m19.040s
python -c 'import sys; sys.stdout.write("0\n" * 1000)'
equivalent or the yes|head
approach).
Aug 5, 2016 at 11:02
python2 -c 'print "0\n" * 1000' > file.txt