Question

Is there any differences between “: > file” and “> file”?

$ : > file.out
$ ls -l file.out
-rw-rw----   1 user    user             0 Mar 18 21:08 file.out
$ > file.out
$ ls -l  file.out
-rw-rw----   1 user    user             0 Mar 18 21:08 file.out

Answer 1

: is the shell built-in NO-OP or null operation. So yeah, directing it to a file ends up with an empty file, as does directing nothing to a file. There’s a sense, I suppose, in which your source is a different kind of nothing, but the result is the same. According to the advanced Bash scripting guide, the “> file.out” formulation won’t work on some systems.

Note that in both cases (unlike “touch”) the file contents will be replaced with nothing if the file already exists.