Why doesn't find let me match multiple patterns?

You need to use parentheses in your find command to group your conditions, otherwise only 2nd -name option is effective for -exec command.

find . \( -name '*.html' -or -name '*.xml' \) -exec echo {} \;

find utility

-print == default

If you just want to print file path and names, you have to drop exec echo, because -print is default.:

find . -name '*.html' -or -name '*.xml'

Order dependency

Otherwise, find is read from left to right, argument order is important!

So if you want to specify something, respect and and or precedence:

find . -name '*.html' -exec echo ">"{} \;  -o -name '*.xml' -exec echo "+"{} \;

or

find . -maxdepth 4 \( -name '*.html' -o -name '*.xml' \) -exec echo {} \;

Expression -print0 and xargs command.

But, for most cases, you could consider -print0 with xargs command, like:

find . \( -name '*.html' -o -name '*.xml' \) -print0 |    xargs -0 printf -- "-- %s -\n"

The advantage of doing this is:

• Only one (or few) fork for thousand of entry found. (Using -exec echo {} \; implies that one subprocess is run for each entry found, while xargs will build a long line with as many argument one command line could hold...)

• In order to work with filenames containing special character or whitespace, -print0 and xargs -0 will use the NULL character as the filename delimiter.

find ... -exec ... {} ... +

From some years ago, find command accept a new syntax for -exec switch.

Instead of \;, -exec switch could end with a plus sign +.

find . \( -name '*.html' -o -name '*.xml' \) -exec printf -- "-- %s -\n" {} +

With this syntax, find will work like xargs command, building long command lines for reducing forks.