Redirection in tcsh

In tcsh redirection the ! symbol means overwrite the existing file even if noclobber is set.

if noclobber is set then:

• cmd > file will write stdout to file if file does not exist
• cmd > file will fail if file exists
• cmd >> file will append stdout to file if file exists
• cmd >> file will fail if file does not exist
• cmd >! file will write stdout to file, overwriting any existing file
• cmd >>! file will append stdout to file, creating the file if it does not already exist

If noclobber is not set then the ! has no effect:

• cmd > file will write stdout to file, overwriting any existing file
• cmd >> file will append stdout to file
• cmd >! file will write stdout to file, overwriting any existing file
• cmd >>! file will append stdout to file