readelf

stub

"X Selection" and VI Register

There are three documented X selections:

• PRIMARY (which is expected to represent the current visual selection); 
• SECONDARY (which is ill-defined);
• CLIPBOARD (which is expected to be used for cut, copy and paste operations).

Of these three, Vim uses

• PRIMARY when reading and writing the "* register
• CLIPBOARD when reading and writing the "+ register.  
• Vim does not access the SECONDARY selection.

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