Denys Vlasenko | a62bc80 | 2016-10-03 00:06:55 +0200 | [diff] [blame^] | 1 | # What should happen if non-interactive shell gets SIGINT? |
| 2 | |
| 3 | (sleep 1; echo Sending SIGINT to main shell PID; exec kill -INT $$) & |
| 4 | |
| 5 | # We create a child which exits with 0 even on SIGINT |
| 6 | # (The complex command is necessary only if SIGINT is generated by ^C, |
| 7 | # in this testcase even bare "sleep 2" would do because |
| 8 | # in the testcase we don't send SIGINT *to the child*...) |
| 9 | $THIS_SH -c 'trap "exit 0" SIGINT; sleep 2' |
| 10 | |
| 11 | # In one second, we (main shell) get SIGINT here. |
| 12 | # The question is whether we should, or should not, exit. |
| 13 | |
| 14 | # bash will not stop here. It will execute next command(s). |
| 15 | |
| 16 | # The rationale for this is described here: |
| 17 | # http://www.cons.org/cracauer/sigint.html |
| 18 | # |
| 19 | # Basically, bash will not exit on SIGINT immediately if it waits |
| 20 | # for a child. It will wait for the child to exit. |
| 21 | # If child exits NOT by dying on SIGINT, then bash will not exit. |
| 22 | # |
| 23 | # The idea is that the following script: |
| 24 | # | emacs file.txt |
| 25 | # | more cmds |
| 26 | # User may use ^C to interrupt editor's ops like search. But then |
| 27 | # emacs exits normally. User expects that script doesn't stop. |
| 28 | # |
| 29 | # This is a nice idea, but detecting "did process really exit |
| 30 | # with SIGINT?" is racy. Consider: |
| 31 | # | bash -c 'while true; do /bin/true; done' |
| 32 | # When ^C is pressed while bash waits for /bin/true to exit, |
| 33 | # it may happen that /bin/true exits with exitcode 0 before |
| 34 | # ^C is delivered to it as SIGINT. bash will see SIGINT, then |
| 35 | # it will see that child exited with 0, and bash will NOT EXIT. |
| 36 | |
| 37 | # Therefore we do not implement bash behavior. |
| 38 | # I'd say that emacs need to put itself into a separate pgrp |
| 39 | # to isolate shell from getting stray SIGINTs from ^C. |
| 40 | |
| 41 | echo Next command after SIGINT was executed |