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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...
294
To use here-document in any bash script, you have to use the symbol << followed by any delimiting identifier after any bash command and close the HereDoc by using the same delimiting identifier at the end of the text.
A HereDoc is a multiline string or a file literal for sending input streams to other commands and programs. HereDocs are especially useful when redirecting multiple commands at once, which helps make Bash scripts neater and easier to understand.
cat with <<EOF>> will create or append the content to the existing file, won't overwrite. whereas cat with <<EOF> will create or overwrite the content.
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.
184
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
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.
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