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Re^4: UNIX command - remove 0 byte file
by Anonymous Monk on Sep 23, 2005 at 12:48 UTC
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A potential problem with using xargs is that although it means only one execution of rm which bodes better performance, it also converts everything read in from the pipe into a single argument list
No, it doesn't. xargs is smart enough that it knows the system limits, and splits of the task into several processes if needed. That's the beauty of xargs.
$ find /opt/perl -print0 2> /dev/null | xargs -0 | wc -l
42
$
Split up into 42 calls to /bin/echo (the default for xargs). Note also the use of -print0 and -0, that eliminates problems with filenames containing whitespace. | [reply]
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Note also the use of -print0 and -0, that eliminates problems with filenames containing whitespace.
I think that those are Linux-only features as well. I sure like them when I can use them, though. :)
thor
Feel the white light, the light within
Be your own disciple, fan the sparks of will
For all of us waiting, your kingdom will come
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Actually, they are not Linux-only feature. At worst, they are GNU-only features, and the GNU file/shell utilities happely run on all commonly used Unix platforms. And they work on Windows as well.
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Let's not forget the OP specifically said 'unix' rather than linux. Filenames with whitespace not being handled with xargs is certainly going to be a problem if this is supposed to be a generic solution. But if the whole file is enclosed in quotes when it has whitespace, rm will handle the argument list properly even if it went thru xargs:
find /path/ -size 0 | perl -e 'while(<>) { chop; s/^(.*\s.*)$/\"$1\"/;
+ print "$_\n"; }' | xargs -n <whatever-filecount-limit> rm
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Except that you now have problems if the filename contains double quotes. Or backquotes. Or dollars. If you want to do the quoting yourself, better wrap the arguments in single quotes, after first escaping any single quotes:
find /path/ -size 0 |
perl -ple 's/\x27/\x27"\x27"\x27/g; "\x27$_\x27"' |
xargs -n ... rm
Note the use of \x27 for single quote, lest it ends the argument to perl.
Of course, if you're going to pipe into perl, there's not much point in calling xargs rm is there? Might as well do the removal from within perl:
find /path/ -size 0 | perl -nle 'unlink or warn "unlink $_: $!\n"'
Note that both pieces of code given above still fail on filenames containing newlines. | [reply]
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I looked into this for xargs under Solaris and the manual makes no such claim, although it looks like you can do something similar manually using a combination of -l -s and -n options, assuming you know the system limits to target these parameters for.
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Re^4: UNIX command - remove 0 byte file
by mhacker (Sexton) on Sep 23, 2005 at 12:55 UTC
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Actually, xargs is supposed to handle that. It will break the command line when it gets too long (1024 words, I think) and run the command again.
But the most annoying thing with xargs is that it doesn't handle spaces or other special characters well:
server:~> ls
a file
server:~> ls | xargs rm
a: No such file or directory
file: No such file or directory
You're forced to do tricks with sed (or perl -e) to get this to work. | [reply]
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GNU xargs offers -i to deal with spaces.
ls | xargs -i ls
XargFoo | [reply]
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