Running an application and \set'ing its output in a variable requires use of
the backtick '`' operator. Under the heading "SQL INTERPOLATION", the
examples should be as follows (the difference being use of backticks instead
of single quotes around the command to be executed):
Current (wrong):
testdb=> \set content '\'' 'cat my_file.txt' '\''
Correct:
testdb=> \set content '\'' `cat my_file.txt` '\''
Current (wrong):
testdb=> \set content 'sed -e "s/'/\\\\\\'/g" < my_file.txt'
Correct:
testdb=> \set content `sed -e "s/'/\\\\\\'/g" < my_file.txt`
Cheers,
Derrell