Unix brace expansion within find command - linux

Question

This is working fine:
$ echo email_{ldn,nyk,asp}.log
Similarly, I wanted to find filenames which differ slightly:
$ find ~ -type f -name email_{ldn,nyk,asp}.log
But above command results in error:
find: paths must precede expression: email_nyk.log
Any help on brace expansions within find command will be very much appreciated.

Answer 1

The error message results from the expansion of the pattern by your shell.
Assuming you have the files email_ldn.log, email_nyk.log and email_asp.log in your current directory, your command
find ~ -type f -name email_{ldn,nyk,asp}.log
will be expanded to
find ~ -type f -name email_ldn.log email_nyk.log email_asp.log
which results in the error message.
To prevent the expansion of a pattern by the shell you have to quote the pattern. Unfortunately, find doesn't support patterns with a list of alternatives in braces, so using this pattern with find will not work as you might expect.
find ~ -type f -name "email_{ldn,nyk,asp}.log" # Does not work as intended.
find ~ -type f -name "email_*.log" # This would work, but matches other files as well.
If you have GNU find, you could use a regular expression instead.
find ~ -type f -regextype posix-extended -regex ".*/email_(ldn|nyk|asp).log"

Answer 2

Brace expansion is not the way to do this sort of thing, and eval is evil, but you could do:
eval find ~ -type f -and \\\( -false "-or -name "email_{ldn,nyk,asp}.log \\\)
The main idea is that -name email_ldn.log email_nyk.log email_asp.log does not work, because you want the expression to be -name email_ldn.log -or -name email_nyk.log -or -name email_asp.log, so you create that expression with the brace expansion. But then find receives -or -name email_???.log as a single argument instead of 3 arguments, so you need to force word splitting with eval. Overall, a nasty, ugly solution.

Answer 3

If you want to find all files with one prefix you can use this command:
find ~ -type f -name "email_*.log"
In this situation you don't need to use braces. Don't forget to put " (quotes) before and after the pattern of the name.
find doesn't support braces to set alternatives, like the shell does. So, if you want to find specific files, you can do this in 2 steps: first find all files with 'email' prefix and then grep for specific files. Try this:
find ~ -type f -name "email*" | egrep "email_(ldn|asp|nyk).log"

Answer 4

It was realized eventually during the conquest, some of you have suggested using eval, but I think it would better to use xargs :
As the aim is to find files matching the brace expansion and execute few command thereafter, so xargs suites this purpose nicely.
$ ls ~/email_{ldn,nyk,asp}.log | xargs -I %% sh -c 'chomd 644 %% && cp -arf %% ~/feed_dir'