On 4/14/19 1:28 AM, Paul Wise wrote:
> Hi folks,
>
> I wanted a way in bash to print the status of the last command I ran,
> including information about each command in a pipe and about signals.
>
> I noticed that bash does not have the ability to display a command
> result, so I came up with the attached prompt configuration.
>
> I am hoping that folks here are interested in fixing the things that I
> found that I had to workaround:
>
> * The command number variable $# is not available at the time that the
> PROMPT_COMMAND is run, only when $PS1 is evaluated.
That's the number of positional parameters.
> * There isn't an easy way to detect no command run yet, syntax errors,
> Ctrl+C, Enter etc versus a command being run and exiting
Syntax errors set $? to 2. SIGINT at the prompt sets $? to 130. There's
no way to determine whether or not those exit statuses differ from an
exit status resulting from a command being run.
> * Sometimes PIPESTATUS isn't reset even though $? has been reset
PIPESTATUS doesn't get set until a job completes. $? will be reset to
128+SIGNUM when a job stops, since that is what shells do and it seems
reasonable as a way to let the user know a job suspended. It doesn't seem
particularly useful to set PIPESTATUS to, e.g., {146, 146, 146} in this
case, though.
>
> I am hoping that folks here have suggestions or fixes for the
> things that I found I wasn't able to do:
>
> * Determine if a command exited normally or due to a signal, even if
> it exited normally with an exit code greater than 128.
There is no way to distinguish these cases. There is a lot of convention
at work here, and convention is that well-behaved programs don't exit with
a status greater than 128.
> * Have the PIPESTATUS be correct after a Ctrl+Z.
See above. You could add logic if $? == 128+SIGTSTP.
> * Differentiate between Ctrl+C Ctrl+C and Ctrl+C Enter.
The tool you have is the exit status of the last command. From that
perspective, there's no difference.
--
``The lyf so short, the craft so long to lerne.'' - Chaucer
``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, UTech, CWRU c...@case.edu http://tiswww.cwru.edu/~chet/
