Make xargs handle filenames that contain spaces

Question

$ ls *mp3 | xargs mplayer  

Playing Lemon.  
File not found: \'Lemon\'  
Playing Tree.mp3.  
File not found: \'Tree.mp3\'  

Exiting... (End of file)  

Answer 1

I know that I'm not answering the xargs question directly but it's worth mentioning find's -exec option.

Given the following file system:

[root@localhost bokeh]# tree --charset assci bands
bands
|-- Dream\ Theater
|-- King's\ X
|-- Megadeth
`-- Rush

0 directories, 4 files

The find command can be made to handle the space in Dream Theater and King's X. So, to find the drummers of each band using grep:

[root@localhost]# find bands/ -type f -exec grep Drums {} +
bands/Dream Theater:Drums:Mike Mangini
bands/Rush:Drums: Neil Peart
bands/King's X:Drums:Jerry Gaskill
bands/Megadeth:Drums:Dirk Verbeuren

In the -exec option {} stands for the filename including path. Note that you don't have to escape it or put it in quotes.

The difference between -exec's terminators (+ and \;) is that + groups as many file names that it can onto one command line. Whereas \; will execute the command for each file name.

So, find bands/ -type f -exec grep Drums {} + will result in:

grep Drums "bands/Dream Theater" "bands/Rush" "bands/King's X" "bands/Megadeth"

and find bands/ -type f -exec grep Drums {} \; will result in:

grep Drums "bands/Dream Theater"
grep Drums "bands/Rush"
grep Drums "bands/King's X"
grep Drums "bands/Megadeth"

In the case of grep this has the side effect of either printing the filename or not.

[root@localhost bokeh]# find bands/ -type f -exec grep Drums {} \;
Drums:Mike Mangini
Drums: Neil Peart
Drums:Jerry Gaskill
Drums:Dirk Verbeuren

[root@localhost bokeh]# find bands/ -type f -exec grep Drums {} +
bands/Dream Theater:Drums:Mike Mangini
bands/Rush:Drums: Neil Peart
bands/King's X:Drums:Jerry Gaskill
bands/Megadeth:Drums:Dirk Verbeuren

Of course, grep's options -h and -H will control whether or not the filename is printed regardless of how grep is called.

---

xargs

xargs can also control how man files are on the command line.

xargs by default groups all the arguments onto one line. In order to do the same thing that -exec \; does use xargs -l. Note that the -t option tells xargs to print the command before executing it.

[root@localhost bokeh]# find ./bands -type f  | xargs -d '\n' -l -t grep Drums
grep Drums ./bands/Dream Theater 
Drums:Mike Mangini
grep Drums ./bands/Rush 
Drums: Neil Peart
grep Drums ./bands/King's X 
Drums:Jerry Gaskill
grep Drums ./bands/Megadeth 
Drums:Dirk Verbeuren

See that the -l option tells xargs to execute grep for every filename.

Versus the default (i.e. no -l option):

[root@localhost bokeh]# find ./bands -type f  | xargs -d '\n'  -t grep Drums
grep Drums ./bands/Dream Theater ./bands/Rush ./bands/King's X ./bands/Megadeth 
./bands/Dream Theater:Drums:Mike Mangini
./bands/Rush:Drums: Neil Peart
./bands/King's X:Drums:Jerry Gaskill
./bands/Megadeth:Drums:Dirk Verbeuren

xargs has better control on how many files can be on the command line. Give the -l option the max number of files per command.

[root@localhost bokeh]# find ./bands -type f  | xargs -d '\n'  -l2 -t grep Drums
grep Drums ./bands/Dream Theater ./bands/Rush 
./bands/Dream Theater:Drums:Mike Mangini
./bands/Rush:Drums: Neil Peart
grep Drums ./bands/King's X ./bands/Megadeth 
./bands/King's X:Drums:Jerry Gaskill
./bands/Megadeth:Drums:Dirk Verbeuren
[root@localhost bokeh]# 

See that grep was executed with two filenames because of -l2.