Note:
The question (how to write a here document (aka heredoc) to a file in a bash script?) has (at least) 3 main independent dimensions or subquestions:
root) own the file?(There are other dimensions/subquestions which I don't consider important. Consider editing this answer to add them!) Here are some of the more important combinations of the dimensions of the question listed above, with various different delimiting identifiers--there's nothing sacred about EOF, just make sure that the string you use as your delimiting identifier does not occur inside your heredoc:
To overwrite an existing file (or write to a new file) that you own, substituting variable references inside the heredoc:
cat << EOF > /path/to/your/file
This line will write to the file.
${THIS} will also write to the file, with the variable contents substituted.
EOF
To append an existing file (or write to a new file) that you own, substituting variable references inside the heredoc:
cat << FOE >> /path/to/your/file
This line will write to the file.
${THIS} will also write to the file, with the variable contents substituted.
FOE
To overwrite an existing file (or write to a new file) that you own, with the literal contents of the heredoc:
cat << 'END_OF_FILE' > /path/to/your/file
This line will write to the file.
${THIS} will also write to the file, without the variable contents substituted.
END_OF_FILE
To append an existing file (or write to a new file) that you own, with the literal contents of the heredoc:
cat << 'eof' >> /path/to/your/file
This line will write to the file.
${THIS} will also write to the file, without the variable contents substituted.
eof
To overwrite an existing file (or write to a new file) owned by root, substituting variable references inside the heredoc:
cat << until_it_ends | sudo tee /path/to/your/file
This line will write to the file.
${THIS} will also write to the file, with the variable contents substituted.
until_it_ends
To append an existing file (or write to a new file) owned by user=foo, with the literal contents of the heredoc:
cat << 'Screw_you_Foo' | sudo -u foo tee -a /path/to/your/file
This line will write to the file.
${THIS} will also write to the file, without the variable contents substituted.
Screw_you_Foo
When root permissions are required for the destination file, use |sudo tee instead of >:
cat << 'EOF' |sudo tee /tmp/yourprotectedfilehere
The variable $FOO will *not* be interpreted.
EOF
cat << "EOF" |sudo tee /tmp/yourprotectedfilehere
The variable $FOO *will* be interpreted.
EOF
I like this method for concision, readability and presentation in an indented script:
<<-End_of_file >file
? foo bar
End_of_file
Where ? is a tab character.
Instead of using cat and I/O redirection it might be useful to use tee instead:
tee newfile <<EOF
line 1
line 2
line 3
EOF
It's more concise, plus unlike the redirect operator it can be combined with sudo if you need to write to files with root permissions.
As instance you could use it:
First(making ssh connection):
while read pass port user ip files directs; do
sshpass -p$pass scp -o 'StrictHostKeyChecking no' -P $port $files $user@$ip:$directs
done <<____HERE
PASS PORT USER IP FILES DIRECTS
. . . . . .
. . . . . .
. . . . . .
PASS PORT USER IP FILES DIRECTS
____HERE
Second(executing commands):
while read pass port user ip; do
sshpass -p$pass ssh -p $port $user@$ip <<ENDSSH1
COMMAND 1
.
.
.
COMMAND n
ENDSSH1
done <<____HERE
PASS PORT USER IP
. . . .
. . . .
. . . .
PASS PORT USER IP
____HERE
Third(executing commands):
Script=$'
#Your commands
'
while read pass port user ip; do
sshpass -p$pass ssh -o 'StrictHostKeyChecking no' -p $port $user@$ip "$Script"
done <<___HERE
PASS PORT USER IP
. . . .
. . . .
. . . .
PASS PORT USER IP
___HERE
Forth(using variables):
while read pass port user ip fileoutput; do
sshpass -p$pass ssh -o 'StrictHostKeyChecking no' -p $port $user@$ip fileinput=$fileinput 'bash -s'<<ENDSSH1
#Your command > $fileinput
#Your command > $fileinput
ENDSSH1
done <<____HERE
PASS PORT USER IP FILE-OUTPUT
. . . . .
. . . . .
. . . . .
PASS PORT USER IP FILE-OUTPUT
____HERE
For future people who may have this issue the following format worked:
(cat <<- _EOF_
LogFile /var/log/clamd.log
LogTime yes
DatabaseDirectory /var/lib/clamav
LocalSocket /tmp/clamd.socket
TCPAddr 127.0.0.1
SelfCheck 1020
ScanPDF yes
_EOF_
) > /etc/clamd.conf
If you want to keep the heredoc indented for readability:
$ perl -pe 's/^\s*//' << EOF
line 1
line 2
EOF
The built-in method for supporting indented heredoc in Bash only supports leading tabs, not spaces.
Perl can be replaced with awk to save a few characters, but the Perl one is probably easier to remember if you know basic regular expressions.
To build on @Livven's answer, here are some useful combinations.
variable substitution, leading tab retained, overwrite file, echo to stdout
tee /path/to/file <<EOF
${variable}
EOF
no variable substitution, leading tab retained, overwrite file, echo to stdout
tee /path/to/file <<'EOF'
${variable}
EOF
variable substitution, leading tab removed, overwrite file, echo to stdout
tee /path/to/file <<-EOF
${variable}
EOF
variable substitution, leading tab retained, append to file, echo to stdout
tee -a /path/to/file <<EOF
${variable}
EOF
variable substitution, leading tab retained, overwrite file, no echo to stdout
tee /path/to/file <<EOF >/dev/null
${variable}
EOF
the above can be combined with sudo as well
sudo -u USER tee /path/to/file <<EOF
${variable}
EOF
Source: Stackoverflow.com