Generate a random string of letters and numbers

Random_String_for_Filenames.sh

#!/bin/bash
# I needed a unique random name for files generated by scripts
# so they don't get overwritten on subsequent compiles
# use mktemp to generate a randomly named tmp directory, save the name to a variable
BASE=$(mktemp)
echo $BASE # the output looks like this: /tmp/tmp.XMbgXwwviZ

# we only want the base random string, not the file path
# use these two steps to strip out the file path
BASE2=${BASE///tmp}
BASE3=${BASE2//./}
echo $BASE3 # the output looks like this: XMbgXwwviZ
# we can now use $BASE3 in the filename of files created by scripts

echo "This is a file" > ~/"$BASE3".txt
cat  ~/"$BASE3".txt # This is a file

# in order to preserve it for use later in the script, we will save it
echo $BASE3 > ~/BASE3_tmp.txt 
# note that this is using "BASE3.txt" and not "$BASE3.txt";
# this is so that a script will be able to find the entry

# later, we can retrieve it
BASE4=$(cat ~/BASE3_tmp.txt)
echo $BASE4 # XMbgXwwviZ