On Tue, Mar 14, 2017 at 9:07 PM, Chet Ramey <chet.ra...@case.edu> wrote:
> when PS1 is expanded the first time, the "current" history entry is the
> one corresponding to the last command entered
> PS2 looks at the current history entry, which is 530 since we've
> started on it.
I think I'm missing something. It seems that when PS1 is expanded \! *does*
match what will eventually become the history number of the command-to-be-
-entered, while PS2 does not. i.e. I can't see how we've started on the second
line of history if the current input will still be stored in the first.
$ PS1='\! $ ' PS2=${PS1/$/>}; history -c
1 $ : 1.1 \
2 > : 1.2
2 $ fc -l -1
1 : 1.1 : 1.2
> When the first line is entered, the history number and command numbers
> get incremented
There seems to be a mismatch: the history number is incremented and the
command number is not:
$ PS1='\! \# $ ' PS2=${PS1/$/>} HISTFILE= $BASH --norc -i <<<$':\\\n'
1 1 $ :\
2 1 >
> I'm not sure what the question is.
Fair enough; sorry for the vague report. I thought it was surprising that:
1. \! and \# increment at different times during command entry
2. The docs refer only to a point in a command's lifecycle at which a prompt
is displayed and then to a history/command number of "this command":
PS0 [...] expanded and displayed after reading a command and before the
command is executed
PS2 [...] expanded as with PS1 [...]
PS4 [...] expanded as with PS1 and the value is printed before each
command bash displays during an execution trace
\! the history number of this command
\# the command number of this command
The history number of a command is its position in the history list [...]
while the command number is the position in the sequence of commands
executed during the current shell session.
Bash expands and displays PS1 before reading the first line of a command
and expands and displays PS2 before reading [...] subsequent lines [...]
Bash displays PS0 after it reads a command but before executing it.
This makes clear that the expansions do happen at different times so e.g. \t
should differ since the time changes between the prompts' expansions.
However, a literal reading of the above suggests that `this command' is the
same in all cases and so it's not clear why \! and !# differ. Perhaps instead
saying of "number of this command" something like "number of the next command
to be read" would be more correct.
