From my understanding, the following should mean exactly the same: ls -1 | xargs file {} ls -1 | xargs -I{} file {} if -I option is not specified, it is default to -I{}. I want to list all files in the current directory and run file command on each of them. Some have spaces in their names. However, I noticed the difference. See below: $ ls -1 Hello World $ ls -1 | xargs file {} {}: ERROR: cannot open `{}' (No such file or directory) Hello: ERROR: cannot open `Hello' (No such file or directory) World: ERROR: cannot open `World' (No such file or directory) $ ls -1 | xargs -I{} file {} Hello World: directory With -I{} explicitly specified, blanks in file names are treated as expected.