问题
I'm taking a unix/linux class and we have yet to learn variables or functions. We just learned some basic utilities like the flag and pipeline, output and append to file. On the lab assignment he wants us to find the largest files and copy them to a directory.
I can get the 5 largest files but I don't know how to pass them into cp in one command
ls -SF | grep -v / | head -5 | cp ? Directory
回答1:
It would be:
cp `ls -SF | grep -v / | head -5` Directory
assuming that the pipeline is correct. The backticks substitute in the line the output of the commands inside it.
You can also make your tests:
cp `echo a b c` Directory
will copy all a, b, and c into Directory.
回答2:
I would do:
cp $(ls -SF | grep -v / | head -5) Directory
xargs would probably be the best answer though.
ls -SF | grep -v / | head -5 | xargs -I{} cp "{}" Directory
回答3:
Use backticks `like this` or the dollar sign $(like this) to perform command substitution. Basically this pastes each line of standard ouput of the backticked command into the surrounding command and runs it. Find out more in the bash manpage under "Command Substitution."
Also, if you want to read one line at a time you can read individual lines out of a pipe stream using "while read" syntax:
ls | while read varname; do echo $varname; done
回答4:
If your cp has a "-t" flag (check the man page), that simplifies matters a bit:
ls -SF | grep -v / | head -5 | xargs cp -t DIRECTORY
The find command gives you more fine-grained ability to get what you want, instead of ls | grep that you have. I'd code your question like this:
find . -maxdepth 1 -type f -printf "%p\t%s\n" |
sort -t $'\t' -k2 -nr |
head -n 5 |
cut -f 1 |
xargs echo cp -t DIRECTORY
来源：https://stackoverflow.com/questions/6833582/pass-output-as-an-argument-for-cp-in-bash