How to install a bash function containing variables using a bash script? [duplicate]

Question

This question already has an answer here:

• How to avoid heredoc expanding variables? [duplicate] 2 answers

I am attempting to create a bash script that will allow me to install the same bash function across multiple machines. This particular function creates a copy of a file with a timestamp in a backup directory:

filebackup () { cp "${@}" ~/"filebackup/${@}_$(date +%Y-%m-%d_%H:%M:%S).bk"; }

Here is my bash script:

cat <<EOT >> ~/.bashrc
# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

# create a file backup in ~/filebackup/ with timestamp
filebackup () { cp "${@}" ~/"filebackup/${@}_$(date +%Y-%m-%d_%H:%M:%S).bk"; }
EOT

source ~/.bashrc

When I execute the script, however, the ${@} are missing and the $(date +%Y-%m-%d_%H:%M:%S) has been evaluated. Here is what has been appended to the .bashrc file:

# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

# create a file backup in ~/filebackup/ with timestamp
filebackup () { cp "" ~/"filebackup/_2017-01-05_12:07:56.bk"; }

How can I ensure that the function is copied literally into the file?

Answer 1

A here document is treated as a double-quoted string, so parameter expansions and command substitutions are evaluated before the command reads from them. Quote any part of the delimiter to have the here document treated as a single-quoted string.

cat <<\EOT >> ~/.bashrc
# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

# create a file backup in ~/filebackup/ with timestamp
filebackup () { cp "${@}" ~/"filebackup/${@}_$(date +%Y-%m-%d_%H:%M:%S).bk"; }
EOT

By any part, I mean any of the following would work just as well:

• 'EOT'
• E\OT
• "E"OT

et cetera.

Answer 2

Suggested by @thatotherguy in a comment: quote "EOT" on line 1 (but not on line 6).

cat <<"EOT" >> ~/.bashrc
# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

# create a file backup in ~/filebackup/ with timestamp
filebackup () { cp "${@}" ~/"filebackup/${@}_$(date +%Y-%m-%d_%H:%M:%S).bk"; }


EOT

source ~/.bashrc