17.11 Using -exec to Create Custom TestsHere's something that will really make your head spin. Remember that -exec doesn't necessarily evaluate to "true"; it only evaluates to true if the command it executes returns a zero exit status (44.7 ) . You can use this to construct custom find tests. Assume that you want to list files that are "beautiful." You have written a program called beauty that returns zero if a file is beautiful, and non-zero otherwise. (This program can be a shell script (44.11 ) , a perl (37.1 ) script, an executable from a C program, or anything you like.) Here's an example: % In this command, -exec
is just another find
operator.
The only difference is that we care about its value; we're not
assuming that it will always be "true." find
executes
the beauty
command for every file. Then -exec
evaluates
to true when find
is looking at a "beautiful" program, causing
find
to print the filename. (Excuse me, causing find
to
evaluate the -print
. Of course, this ability is capable of infinite variation. If you're interested in finding beautiful C code, you could use the command: % And so on. For performance reasons, it's a good idea to put the -exec operator as close to the end as possible. This avoids starting processes unnecessarily; the -exec command will execute only when the previous operators evaluate to true. - , |
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