Expressions

The expression part can be divided itself in four different groups of keywords: options, tests, actions, and operators. Each of them can return a true/false value, together with a side effect. The difference among the groups is shown below.

options

affect the overall operation of find, rather than the processing of a single file. An example is -follow, which instructs find to follow symbolic links instead of just stating the inode. They always return true.

tests

are real tests (for example, -empty checks whether the file is empty), and can return true or false.

actions

have also a side effect the name of the considered file. They can return true or false too.

operators

do not really return a value (they can conventionally be considered as true), and are used to build compress expression. An example is -or, which takes the logical OR of the two subexpressions on its side. Notice that when juxtaposing expression, a -and is implied.

Note that find relies upon the shell to have the command line parsed; it means that all keyword must be embedded in white space and especially that a lot of nice characters have to be escaped, otherwise they would be mangled by the shell itself. Each escaping way (backslash, single and double quotes) is OK; in the examples the single character keywords will be usually quoted with backslash, because it is the simplest way (at least in my opinion. But it's me who is writing these notes!)