shuf -i 1-100 -n 1
echo $RANDOM

'RANDOM'
     Each time this parameter is referenced, a random integer between 0
     and 32767 is generated.  Assigning a value to this variable seeds
     the random number generator.

#!/bin/bash
#Copy file
pf=/home/user/download/pantxt
tf=/home/user/download/last/cremo.txt
randf= ls $pf | shuf -i n1
cp -i $randf $tf

cp "$(ls dirfrom/ | sort -r |head -n1)" dirto/

$ printf "a\nb\nc\nd\ne\nf\n" | sort -R | head -1
e
$ printf "a\nb\nc\nd\ne\nf\n" | sort -R | head -1
a
$ printf "a\nb\nc\nd\ne\nf\n" | sort -R | head -1
d
$ printf "a\nb\nc\nd\ne\nf\n" | sort -R | head -1
d
$ printf "a\nb\nc\nd\ne\nf\n" | sort -R | head -1
b
$ printf "a\nb\nc\nd\ne\nf\n" | sort -R | head -1
e
$ printf "a\nb\nc\nd\ne\nf\n" | sort -R | head -1
b
$ printf "a\nb\nc\nd\ne\nf\n" | sort -R | head -1
a
$ printf "a\nb\nc\nd\ne\nf\n" | sort -R | head -1
f
$ printf "a\nb\nc\nd\ne\nf\n" | sort -R | head -1
f
$ printf "a\nb\nc\nd\ne\nf\n" | sort -R | head -1
e
$ printf "a\nb\nc\nd\ne\nf\n" | sort -R | head -1
a

#!/bin/bash
#Copy file
pf=/home/user/download/pantxt
tf=/home/user/download/last/cremo.txt
cp -i "$(ls $pf | sort -R |head -n1)" $tf