do I need cat to write a heredoc to a file?

Question

I've got a script that writes to a file, like so:

cat >myfile <<EOF
some lines
and more lines
EOF

but I'm not sure whether this is a Useless Use of Cat or not...

Just people like to play the UUOC Superiority Card whenever possible, you don't have to be afraid of `cat`. — Andy Lester, Jan 10 '13 at 23:19

score 8 · Accepted Answer · answered Jun 13 '13 at 17:31

8

Even if this may not be a UUOC, it might be useful to use tee instead:

tee myfile <<EOF
some lines
and more lines
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.

answered Jun 13 '13 at 17:31

Livven

Doesn't this also write to standard out? In most cases this is not desired. – Bogdan Calmac Aug 10 '15 at 21:42
True – if you don't want that, add `> dev/null` to the end of the first line. See also [this comment](http://stackoverflow.com/questions/2953081/how-can-i-write-a-here-doc-to-a-file-in-bash-script/17093489#comment24896950_17093489). – Livven Aug 11 '15 at 16:06

score 2 · Answer 2 · answered Jan 10 '13 at 22:08

2

It is not really a UUOC. You can also do the same with echo:

echo "this is line
this is another line
this is the last line" > somefile

answered Jan 10 '13 at 22:08

jim mcnamara

score 2 · Answer 3 · answered Jan 10 '13 at 22:14

2

UUOC is when you use cat when it is not needed. As in:

cat file | grep "something"

Instead you can do it whithout cat:

grep "something" file

Look here for the original definition of UUOC.

answered Jan 10 '13 at 22:14

jgr

cmh · Answer 4 · 2013-01-10T22:52:12.877

2

In zsh it is a UUOC because:

>myfile <<EOF
some lines
and more lines
EOF

Works fine.

edited Jan 10 '13 at 22:52

answered Jan 10 '13 at 22:39

cmh

4 Answers4