minor documentation update on SIGINT handling

doc/bash.1

@@ -5,12 +5,12 @@
 .\"	Case Western Reserve University
 .\"	chet.ramey@case.edu
 .\"
-.\"	Last Change: Fri Oct  8 14:10:30 EDT 2021
+.\"	Last Change: Tue Oct 19 11:34:57 EDT 2021
 .\"
 .\" bash_builtins, strip all but Built-Ins section
 .if \n(zZ=1 .ig zZ
 .if \n(zY=1 .ig zY
-.TH BASH 1 "2021 October 8" "GNU Bash 5.1"
+.TH BASH 1 "2021 October 19" "GNU Bash 5.1"
 .\"
 .\" There's some problem with having a `@'
 .\" in a tagged paragraph with the BSD man macros.
@@ -5214,6 +5214,63 @@ When \fBbash\fP is waiting for an asynchronous command via the \fBwait\fP
 builtin, the reception of a signal for which a trap has been set will
 cause the \fBwait\fP builtin to return immediately with an exit status
 greater than 128, immediately after which the trap is executed.
+.PP
+When job control is not enabled, and \fBbash\fP is waiting for a foreground
+command to complete, the shell receives keyboard-generated signals
+such as
+.SM
+.B SIGINT
+(usually generated by \fB^C\fP) that users commonly intend to send
+to that command.
+This happens because the shell and the command are in the
+same process group as the terminal, and \fB^C\fP sends
+.SM
+.B SIGINT
+to all processes in that process group.
+.PP
+When \fBbash\fP is running without job control enabled and receives 
+.SM
+.B SIGINT
+while waiting for a foreground command, it waits until that foreground
+command terminates and then decides what to do about the
+.SM
+.BR SIGINT :
+.IP 1.
+If the command terminates due to the
+.SM
+.BR SIGINT ,
+\fBbash\fP concludes
+that the user meant to end the entire script, and acts on the
+.SM
+.B SIGINT
+(e.g., by running a
+.SM
+.B SIGINT
+trap or exiting itself);
+.IP 2.
+If the command does not terminate due to
+.SM
+.BR SIGINT ,
+the program handled the
+.SM
+.B SIGINT
+itself and did not treat it as a fatal signal.
+In that case, \fBbash\fP does not treat
+.SM
+.B SIGINT
+as a fatal signal, either, instead assuming that the
+.SM
+.B SIGINT
+was used as part of the program's normal operation
+(e.g., emacs uses it to abort editing
+commands) or deliberately discarded.
+However, \fBbash\fP will run any
+trap set on
+.SM
+.BR SIGINT ,
+as it does with any other trapped signal it
+receives while it is waiting for the foreground command to
+complete, for compatibility.
 .SH "JOB CONTROL"
 .I Job control
 refers to the ability to selectively stop (\fIsuspend\fP)
@@ -10131,6 +10188,8 @@ history is enabled, as described above under
 .B compat43
 .TP 8
 .B compat44
+.TP 8
+.B compat50
 .PD
 These control aspects of the shell's compatibility mode
 (see