# 
# Snippet: Add a prefix before each line, except the first one.
# 
# This migjt be useful if you write the output of a
# command to a logfile including a timestamp printed
# before, but you want all lines to be indented to
# match the length of the timestamp.
# 


# 
# The message containing multiple lines.
# 
msg="This is a message
with multiple lines."


# 
# Length of the timestamp
# 
timestamp_length=$(date --iso-8601=seconds | tr -d "\n" | wc -c)


# 
# The prefix for continued lines: Repeated spaces
# We need 4 more spaces than $timestamp_length because
# of the brackets and two spaces added to the timestamp.
# 
# @see https://unix.stackexchange.com/questions/188658/writing-a-character-n-times-using-the-printf-command
# 
line_prefix=$(yes " " | head -$((timestamp_length + 4)) | tr -d "\n")


# 
# Print the timestamp
# 
printf "[$(date --iso-8601=seconds)]  "


# 
# Prefix each line of $msg with $line_prefix, except for the first one.
# 
# NOTE: The AWK script spans pver multiple lines for better readability.
# 
echo "${msg}" | awk "{
	if (NR >= 2) {
			print \"${line_prefix}\"$0;
	} else {
			print $0;
	}
}"


# 
# The same command as above, but in one line
# 
echo "${msg}" | awk "{ if (NR >= 2) { print \"${line_prefix}\"$0; } else { print $0;} }"