Tenth Line

How would you print just the 10th line of a file?

For example, assume that file.txt has the following content:

Line 1
Line 2
Line 3
Line 4
Line 5
Line 6
Line 7
Line 8
Line 9
Line 10

Your script should output the tenth line, which is:

Line 10

不知道为何直接写shell一直不通过

# Read from the file file.txt and output the tenth line to stdout.
#sed -n "10 p" file.txt
#awk 'NR==10 {print $0}' file.txt
var=1
for line in `cat file.txt`
    do
       if [ $var -eq 10 ]
       then
           echo $line
       fi
       var='expr $var + 1'
    done