On Tuesday 9 June 2009, 16:36, Neil Bothwick wrote:
> On Tue, 09 Jun 2009 16:15:21 +0200, Joerg Schilling wrote:
> > > find -H /usr/lib /lib -type f | xargs -d'\n' qfile --orphans
> >
> > No, this is definitely wrong: the right way to handle this is
> > execplus (since 19 years).
>
> If it's been around 19 years, why doesn't Google know anything about
> it? What is it?
Well, google does not know everything :)
Basically, using + instead of ; after -exec allows to run the specified
command less times, each time with the highest possible number of
arguments (instead of running it once per file, which is what happens
with ;). And yes, that's been in POSIX for a long time now. Example:
$ ls
file1 file2 file3 file4 file5
$ find . -type f -exec sh -c 'echo "number of arguments: $#"' sh {} \;
number of arguments: 1
number of arguments: 1
number of arguments: 1
number of arguments: 1
number of arguments: 1
$ find . -type f -exec sh -c 'echo "number of arguments: $#"' sh {} +
number of arguments: 5
So when you have to run a command on a very big number of files, say 1000
or more, with ; you spawn 1000 processes, with + you span just one or
two (well, depending on the maximum command line length on the system
anyway). This is of course much less resource intensive.
Basically, using -exec with + does what xargs does, but without the need
to care for strange characters in file names (well, a bit simplified,
but you get the idea).
