Shell Programming and Scripting

Greetings

Got a basic one to muddle through tonight; and hoping for a smidgen of help 'long the way

Here 'tis:

Code:

ls ./dir1/ | grep -i .jpg | xargs cp -f ./dir1/$1 ../../dir2/$1

Simple enough; and to this amateur eye, it looks like things should work pretty well. But, of course, it tanks out...

What's the jot or tittle I might be missing this time?


Thanks a bunch!

Maybe

Code:

ls ./dir1/*.jpg | xargs -I file cp -f file ../../dir2/

xargs is not a shell. It doesn't have a $1, $2, ... They just turn into whatever parameters the shell already had, if any (once and exactly once, before xargs is even run).

To be honest I'm not even sure what you're trying to do, what you expected $1 $2 ... to be.

xargs works like this:

Code:

# These commands are effectively equivalent
cat a b c d e
echo "a b c d e" | xargs cat

I think this might be closer to what you want:

Code:

echo path/* | xargs cp -t /path/to/destfolder

This will expand to cp -t /path/to/destfolder file1 file2 file3 ...

The -t is necessary because, ordinarily, cp expects the folder to come last, not first, which xargs cannot do.

The script you have shown us makes no sense to me at all. Instead of telling us it tanks out, it would be a lot easier to help you if you would tell us what you're trying to do.

As pointed out, xargs doesn't support positional arguments using $1, etc.

What you can do is use -I <replace string> to explictly tell xargs where to put the arguments in the command. It's worth noting that in this case that arguments are separated by newline, not just any whitespace as normal.

@all:

Thank you for the input. My apologies for any confusion, but I was trying to accomplish the same thing which most of us have done at one time or other with DOS's "COPY" commandline to copy select content of one directory over to another.

In the end, Aia's

Code:

ls ./dir1/*.jpg | xargs -I file cp -f file ../../dir2/

worked well; along with Corona688's

Code:

echo ./dir1/*.jpg | xargs cp -t ../../dir2/

My tinkering found, likewise, that

Code:

find ./dir1/ -name '*' | grep -i .jpg | xargs -I file cp -f file ../../dir2/

and

Code:

find ./dir1/ -name '*' | grep -i .jpg | xargs cp -t ../../dir2/

also did the trick using "find".

So I guess there's more than one way to cook a fish; but I can't help but wish there was something syntactically as simple as the old DOS "COPY" command for those of us who have moved along to UNIX...


Thanks again, all; and have a great day