How can I write a heredoc to a file in Bash script?
如何在Bash脚本中将文档写入文件？
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.
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