Re: Behavior of readline() when it encounters EOF

[Chet Ramey]

On 10/6/22 12:59 PM, Andrea Monaco wrote:
> The readline manual says that: "If readline encounters an EOF while
> reading the line, and the line is empty at that point, then (char *)NULL
> is returned. Otherwise, the line is ended just as if a newline had been
> typed" (from lib/readline/doc/rltech.texi).
>
> But the second sentence appears wrong.  When I type Ctrl-D at a readline
> prompt and the line is non-empty, nothing happens.  You can check at any
> readline prompt, including bash.

It's confusing. The ^D character is the stty EOF character, and is a valid
bindable readline key sequence. It's not the same as encountering EOF,
which is indicated by read(2) returning 0.

When readline reads ^D on an empty line, it returns NULL. If it reads
^D and the line isn't empty, it deletes the character following the cursor.
So on an empty line, readline simulates an EOF by returning NULL.

Chet

--
``The lyf so short, the craft so long to lerne.'' - Chaucer
                 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, UTech, CWRU    chet@case.edu    http://tiswww.cwru.edu/~chet/