create_dgst.bsh

#!/bin/bash
# ===========================================================
# create a digial signature (hash) of a file
# ===========================================================
# -sha256     digest type
# -sign $key  digitally sign the digest using a private
#             key
# -out $hash  output file
# $file       file (or files) to digest
# ===========================================================
# for help: openssl dgst -help
# ===========================================================

dir="hashes"
file="gettysburg_address.txt"
hash="hashes/gettysburg_address.sha256"
key="keys/client.key.pem"

# does the hashes directory exists?

if [ ! -d $dir ]; then
   echo
   echo "Hash directory ($dir) does not exists"
   echo
   exit 1
fi

# does the file exists?

if [ ! -f $file ]; then
   echo
   echo "File ($file) does not exist"
   echo
   exit 1
fi

# does the hash already exist?

if [ -f $hash ]; then
   echo
   echo "Hash file ($hash) already exists"
   echo
   exit 1
fi

# does the client key exist?

if [ ! -f $key ]; then
   echo
   echo "Key ($key) does not exist"
   echo
   exit 1
fi

# create hash of file

openssl dgst -sha256 -sign $key -out $hash $file