find: missing argument to `-exec'

GNU find prints find: missing argument to `-exec' when the command after -exec is not terminated. find needs either \; (run the command once per file) or + (run it once with many files) to know where the command ends. The semicolon must be escaped or quoted because the shell otherwise treats it as the end of the whole find command: write find . -name '*.log' -exec rm {} \; or, faster, find . -name '*.log' -exec rm {} +.

Reproduce it

touch a.log b.log
find . -name '*.log' -exec echo {} ;

find: missing argument to `-exec'

The shell removed the ;, so find received -exec echo {} with nothing to close it. A {} that is not directly before + fails the same way:

mkdir dest && touch a.log
find . -maxdepth 1 -name '*.log' -exec cp {} dest/ +

find: missing argument to `-exec'

Fix

touch a.log b.log
echo '--- one command per file'
find . -name '*.log' -exec echo file: {} \; | sort
echo '--- one command for all files'
find . -name '*.log' -exec echo files: {} +

--- one command per file
file: ./a.log
file: ./b.log
--- one command for all files
files: ./a.log ./b.log

With +, find appends as many paths as fit on one command line, which is much faster for thousands of files. Order of the paths depends on the directory, so the block sorts the first output.

{} in the middle of the command

When the file name must not be last (copying into a directory), use an option that takes the target first, or a small shell:

mkdir dest && touch a.log b.log
find . -maxdepth 1 -name '*.log' -exec cp -t dest {} +
find . -maxdepth 1 -name '*.log' -exec sh -c 'for f; do cp "$f" "dest/$f.bak"; done' sh {} +
ls dest

a.log
a.log.bak
b.log
b.log.bak

cp -t is GNU-only; the sh -c form works with any find. The extra sh fills $0, so the file names arrive in $@.

Other ways to lose the terminator

Gluing the semicolon to the braces does not work either: {}\; reaches find as the single word {};, which is not a terminator.

touch a.log
find . -name '*.log' -exec echo {}\;

find: missing argument to `-exec'

The same happens when the find command is built inside a string, for example in ssh host "...", sh -c "..." or a Makefile recipe: each layer of quoting may strip one backslash. Switch to +, which needs no escaping at all, or check the arguments that finally reach find with set -x.

How to recognise the cause

What the error does not mean

The message is about the syntax of the expression, so find exits with status 1 before it visits any file: nothing was deleted, copied or changed. Once the command is terminated correctly, failures of the command itself are different: with \; the command's exit status only acts as a true or false test and find itself still exits 0, while with + a failing command makes find exit non-zero.

Prevent it

Prefer -exec cmd {} + whenever the command accepts many paths: it is faster and has no backslash to forget. For deletions, GNU find's -delete action needs no -exec at all. Test a new expression with -exec echo {} + or -print before replacing echo with a command that changes files.

FAQ