How to send heredoc command to background?
I want to send a heredoc command like this one
cat <<EOF
line 1
line 2
EOF
to background. (The actual command is openssl with many lines of input which takes some time to complete).
The command needs to be storable in string so that I could exec it in PHP.
Simply appending an ampersand doesn’t work:
cat <<EOF
line 1
line 2
EOF &
Any other combinations I tried (putting the command in brackets etc.) don’t work either.
How?
The here-doc operator (<<EOF, here) is just a regular redirection operator, and what comes after it (on the same line!) is still part of the command.
E.g.
# from here-doc to file
cat <<EOF > foo.txt
...
EOF
# here-doc and some arguments to cat
cat <<EOF -n foo.txt
...
EOF
# two here-docs!
cat /dev/fd/3 /dev/fd/4 3<<EOF 4<<EOF
first
EOF
second
EOF
So you’d do the same as if it was just a redirection from a file, put the & at the end of the cat command line:
cat <<EOF &
here-doc text
EOF