Script to remove an entry from the ssh known hosts file

remove_known_host.sh

#!/bin/bash -e

line_num="$1"
if [ -z "$line_num" ]; then
   echo "Usage: $0 <line num>"
   exit 1
fi

known_hosts="${HOME}/.ssh/known_hosts"
tmp_file="${known_hosts}.$$"
trap "rm -f $tmp_file" EXIT

# Sanity checks
if [ -O "${known_hosts}" ]; then
   echo "File $known_hosts does not exists or is not owned by you"
   exit 1
fi
num_lines=`wc -l $known_hosts | awk '{print $1}'`
if [ "$line_num" -gt "$num_lines" ]; then
   echo "Line number $line_num exceeds the number of lines ($num_lines) in $known_hosts"
   exit 1
fi

# Regenerate the known hosts file
(head -`expr ${line_num} - 1` "${known_hosts}" ; tail -`expr ${num_lines} - ${line_num}` ${known_hosts}) > "$tmp_file"
mv "$tmp_file" "$known_hosts"