Actions

I have said that actions are those which actually do something. Well, -prune rather does not do something, i.e. descending the directory tree (unless -depth is given). It is usally find together with -fstype, to choose among the various filesystems which should be checked.

The other actions can be divided into two broad categories;

• Actions which print something. The most obvious of these - and indeed, the default action of find - is -print which just print the name of the file(s) matching the other conditions in the command line, and returns true. A simple variants of -print is -fprint file, which uses file instead of standard output, -ls lists the current file in the same format as ls -dils; -printf format behaves more or less like C function printf(), so that you can specify how the output should be formatted, and -fprintf file format does the same, but writing on file. These action too return true.
• Actions which execute something. Their syntax is a little odd and they are used widely, so please look at them.

  -exec command \; the command is executed, and the action returns true if its final status is 0, that is regular execution of it. The reason for the \; is rather logical: find does not know where the command ends, and the trick to put the exec action at the end of the command is not applicable. Well, the best way to signal the end of the command is to use the character used to do this by the shell itself, that is `;', but of course a semicolon all alone on the command line would be eaten by the shell and never sent to find, so it has to be escaped. The second thing to remember is how to specify the name of the current file within command, as probably you did all the trouble to build the expression to do something, and not just to print date. This is done by means of the string {}. Some old versions of find require that it must be embedded in white space - not very handy if you needed for example the whole path and not just the file name - but with GNU find could be anywhere in the string composing command. And shouldn't it be escaped or quoted, you surely are asking? Amazingly, I never had to do this neither under tcsh nor under bash (sh does not consider { and } as special characters, so it is not much of a problem). My idea is that the shells ``know'' that {} is not an option making sense, so they do not try to expand them, luckily for find which can obtain it untouched.

  -ok command \; behaves like -exec, with the difference that for each selected file the user is asked to confirm the command; if the answer starts with y or Y, it is executed, otherwise not, and the action returns false.