Why are the backslash and semicolon required with

问题:

I have begun to combine different commands in the linux terminal. I am wondering why the backslash and semicolon are required for a command such as:

find ./ -name 'blabla' -exec cp {} ./test \;

when a simple cp command is simply:

cp randomfile ./test

without the \;

Are they to clearly indicate the end of a command, or is it simply required in the documentation? What is the underlying principle?

Thank you!

回答1:

from "man find":

All following arguments to find are taken to be arguments to the command until an argument consisting of ';' is encountered.

find needs to know when the arguments of exec are terminated. It is natural to terminate a shell command with ; because also the shell uses this character. For the very same reason such a character must be escaped when inserted through the shell.

回答2:

The backslash before the semicolon is used, because ; is one of list operators (or &&, ||) for separating shell commands. In example:

command1; command2

The find utility is using ; or + to terminate the shell commands invoked by -exec.

So to avoid special shell characters from interpretation, they need to be escaped with a backslash to remove any special meaning for the next character read and for line continuation.

Therefore the following example syntax is allowed for find command:

find . -exec echo {} \;
find . -exec echo {} ';'
find . -exec echo {} ";"
find . -exec echo {} \+
find . -exec echo {} +

See also:

• Using semicolon (;) vs plus (+) with exec in find
• Simple unix command, what is the {} and \; for