from man bash:
Quote:
Redirecting Output
Redirection of output causes the file whose name results from the
expansion of word to be opened for writing on file descriptor n, or the
standard output (file descriptor 1) if n is not specified. If the file
does not exist it is created; if it does exist it is truncated to zero
size.
The general format for redirecting output is:
[n]>word
If the redirection operator is >, and the noclobber option to the set
builtin has been enabled, the redirection will fail if the file whose
name results from the expansion of word exists and is a regular file.
If the redirection operator is >|, or the redirection operator is > and
the noclobber option to the set builtin command is not enabled, the
redirection is attempted even if the file named by word exists.
|
Seems like it truncates the file before reading it as the input.