diff options
Diffstat (limited to 'shell/ash.c')
| -rw-r--r-- | shell/ash.c | 57 |
1 files changed, 54 insertions, 3 deletions
diff --git a/shell/ash.c b/shell/ash.c index 4360770d4..68aa675e5 100644 --- a/shell/ash.c +++ b/shell/ash.c @@ -4553,7 +4553,52 @@ forkchild(struct job *jp, union node *n, int mode) * Do we do it correctly? */ closescript(); - clear_traps(); + + if (mode == FORK_NOJOB /* is it `xxx` ? */ + && n && n->type == NCMD /* is it single cmd? */ + /* && n->ncmd.args->type == NARG - always true? */ + && strcmp(n->ncmd.args->narg.text, "trap") == 0 + && n->ncmd.args->narg.next == NULL /* "trap" with no arguments */ + /* && n->ncmd.args->narg.backquote == NULL - do we need to check this? */ + ) { + TRACE(("Trap hack\n")); + /* Awful hack for `trap` or $(trap). + * + * http://www.opengroup.org/onlinepubs/009695399/utilities/trap.html + * contains an example where "trap" is executed in a subshell: + * + * save_traps=$(trap) + * ... + * eval "$save_traps" + * + * Standard does not say that "trap" in subshell shall print + * parent shell's traps. It only says that its output + * must have suitable form, but then, in the above example + * (which is not supposed to be normative), it implies that. + * + * bash (and probably other shell) does implement it + * (traps are reset to defaults, but "trap" still shows them), + * but as a result, "trap" logic is hopelessly messed up: + * + * # trap + * trap -- 'echo Ho' SIGWINCH <--- we have a handler + * # (trap) <--- trap is in subshell - no output (correct, traps are reset) + * # true | trap <--- trap is in subshell - no output (ditto) + * # echo `true | trap` <--- in subshell - output (but traps are reset!) + * trap -- 'echo Ho' SIGWINCH + * # echo `(trap)` <--- in subshell in subshell - output + * trap -- 'echo Ho' SIGWINCH + * # echo `true | (trap)` <--- in subshell in subshell in subshell - output! + * trap -- 'echo Ho' SIGWINCH + * + * The rules when to forget and when to not forget traps + * get really complex and nonsensical. + * + * Our solution: ONLY bare $(trap) or `trap` is special. + */ + } else { + clear_traps(); + } #if JOBS /* do job control only in root shell */ doing_jobctl = 0; @@ -4597,8 +4642,14 @@ forkchild(struct job *jp, union node *n, int mode) setsignal(SIGQUIT); } #if JOBS - if (n && n->type == NCMD && strcmp(n->ncmd.args->narg.text, "jobs") == 0) { + if (n && n->type == NCMD + && strcmp(n->ncmd.args->narg.text, "jobs") == 0 + ) { TRACE(("Job hack\n")); + /* "jobs": we do not want to clear job list for it, + * instead we remove only _its_ own_ job from job list. + * This makes "jobs .... | cat" more useful. + */ freejob(curjob); return; } @@ -12208,7 +12259,7 @@ trapcmd(int argc UNUSED_PARAM, char **argv UNUSED_PARAM) if (!*ap) { for (signo = 0; signo < NSIG; signo++) { if (trap[signo] != NULL) { - out1fmt("trap -- %s %s\n", + out1fmt("trap -- %s SIG%s\n", single_quote(trap[signo]), get_signame(signo)); } |