change random line with shellscript
how can i easily (quick and dirty) change, say 10, random lines of a file with a simple shellscript?
i though about abusing ed and generating random commands and line ranges, but i'd开发者_Go百科 like to know if there was a better way
awk 'BEGIN{srand()}
{ lines[++c]=$0 }
END{
while(d<10){
RANDOM = int(1 + rand() * c)
if( !( RANDOM in r) ) {
r[RANDOM]
print "do something with " lines[RANDOM]
++d
}
}
}' file
or if you have the shuf
command
shuf -n 10 $file | while read -r line
do
sed -i "s/$line/replacement/" $file
done
Playing off @Dennis' version, this will always output 10. Doing random numbers in a separate array could create duplicates and, consequently, fewer than 10 modifications.
file=~/testfile
c=$(wc -l < "$file")
awk -v c=$c '
BEGIN {
srand();
count = 10;
}
{
if (c*rand() < count) {
--count;
print "do something with " $0;
} else
print;
--c;
}
' "$file"
This seems to be quite a bit faster:
file=/your/input/file
c=$(wc -l < "$file")
awk -v c=$c 'BEGIN {
srand();
for (i=0;i<10;i++) lines[i] = int(1 + rand() * c);
asort(lines);
p = 1
}
{
if (NR == lines[p]) {
++p
print "do something with " $0
}
else print
}' "$file"
I
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