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authorDenis Vlasenko <vda.linux@googlemail.com>2009-03-31 13:05:32 +0000
committerDenis Vlasenko <vda.linux@googlemail.com>2009-03-31 13:05:32 +0000
commit7b830e78f2ff2ba024ae713c306ab49aa45a435a (patch)
tree84fe895a3663cfe8409705be8d13903e26f092bb
parent422cd7c81c25bdf5155d09aecfe5bd9d5c28a1f7 (diff)
downloadbusybox-7b830e78f2ff2ba024ae713c306ab49aa45a435a.tar.gz
hush: fix comments, no code changes
-rw-r--r--shell/hush.c65
1 files changed, 36 insertions, 29 deletions
diff --git a/shell/hush.c b/shell/hush.c
index 21fa95429..a96b179c6 100644
--- a/shell/hush.c
+++ b/shell/hush.c
@@ -753,14 +753,14 @@ static void free_strings(char **strings)
/* Basic theory of signal handling in shell
* ========================================
- * This does not describe what hush does, rahter, it is current understanding
- * what it _should_ do.
+ * This does not describe what hush does, rather, it is current understanding
+ * what it _should_ do. If it doesn't, it's a bug.
* http://www.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#trap
*
* Signals are handled only after each pipe ("cmd | cmd | cmd" thing)
* is finished or backgrounded. It is the same in interactive and
* non-interactive shells, and is the same regardless of whether
- * a user trap handler is installed or a default one is in effect.
+ * a user trap handler is installed or a shell special one is in effect.
* ^C or ^Z from keyboard seem to execute "at once" because it usually
* backgrounds (i.e. stops) or kills all members of currently running
* pipe.
@@ -770,33 +770,38 @@ static void free_strings(char **strings)
*
* Trap handlers will execute even within trap handlers. (right?)
*
- * User trap handlers are forgotten when subshell is entered.
+ * User trap handlers are forgotten when subshell ("(cmd)") is entered. [TODO]
*
* If job control is off, backgrounded commands ("cmd &")
- * have SIGINT, SIGQUIT set to SIG_IGN.
+ * have SIGINT, SIGQUIT set to SIG_IGN.
*
* Commands run in command substitution ("`cmd`")
- * have SIGTTIN, SIGTTOU, SIGTSTP set to SIG_IGN.
+ * have SIGTTIN, SIGTTOU, SIGTSTP set to SIG_IGN.
*
- * Ordinary commands have IGN/DFL set as inherited by the shell
- * from its parent.
+ * Ordinary commands have signals set to SIG_IGN/DFL set as inherited
+ * by the shell from its parent.
*
- * Default handlers which differ from DFL action
- * (note: subshell is not an interactive shell):
+ * Siganls which differ from SIG_DFL action
+ * (note: child (i.e., [v]forked) shell is not an interactive shell):
*
* SIGQUIT: ignore
* SIGTERM (interactive): ignore
- * SUGHUP (interactive): send SIGCONT to stopped jobs,
- * send SIGHUP to all jobs and exit
+ * SIGHUP (interactive):
+ * send SIGCONT to stopped jobs, send SIGHUP to all jobs and exit
* SIGTTIN, SIGTTOU, SIGTSTP (if job control is on): ignore
- * (note that ^Z is handled not by trapping SIGTSTP, but by seeing
- * that all pipe members are stopped) (right?)
+ * (note that ^Z is handled not by trapping SIGTSTP, but by seeing
+ * that all pipe members are stopped) (right?)
* SIGINT (interactive): wait for last pipe, ignore the rest
- * of the command line, show prompt. (check/expand this)
- * Example 1: this waits 5 sec, but does not execute ls:
- * "echo $$; sleep 5; ls -l" + "kill -INT <pid>"
- * Example 2: this does not wait and does not execute ls:
- * "echo $$; sleep 5 & wait; ls -l" + "kill -INT <pid>"
+ * of the command line, show prompt. NB: ^C does not send SIGINT
+ * to interactive shell while shell is waiting for a pipe,
+ * since shell is bg'ed (is not in foreground process group).
+ * (check/expand this)
+ * Example 1: this waits 5 sec, but does not execute ls:
+ * "echo $$; sleep 5; ls -l" + "kill -INT <pid>"
+ * Example 2: this does not wait and does not execute ls:
+ * "echo $$; sleep 5 & wait; ls -l" + "kill -INT <pid>"
+ * Example 3: this does not wait 5 sec, but executes ls:
+ * "sleep 5; ls -l" + press ^C
*
* (What happens to signals which are IGN on shell start?)
* (What happens with signal mask on shell start?)
@@ -813,14 +818,16 @@ static void free_strings(char **strings)
* unsigned non_DFL_mask: a mask of such "special" signals
* sigset_t blocked_set: current blocked signal set
*
- * "trap - SIGxxx": clear bit in blocked_set unless it is also in non_DFL
- * "trap 'cmd' SIGxxx": set bit in blocked_set (even if 'cmd' is '')
+ * "trap - SIGxxx":
+ * clear bit in blocked_set unless it is also in non_DFL
+ * "trap 'cmd' SIGxxx":
+ * set bit in blocked_set (even if 'cmd' is '')
* after [v]fork, if we plan to be a shell:
- * nothing for {} subshell (say, "true | { true; true; } | true")
- * unset all traps if () shell. [TODO]
+ * nothing for {} child shell (say, "true | { true; true; } | true")
+ * unset all traps if () shell. [TODO]
* after [v]fork, if we plan to exec:
- * POSIX says pending signal mask is cleared in child - no need to clear it.
- * restore blocked signal set to one inherited by shell just prior to exec.
+ * POSIX says pending signal mask is cleared in child - no need to clear it.
+ * Restore blocked signal set to one inherited by shell just prior to exec.
*
* Note: as a result, we do not use signal handlers much. The only use
* is to restore terminal pgrp on exit.
@@ -848,7 +855,6 @@ static void init_signal_mask(void)
#endif
G.non_DFL_mask = mask;
- /*sigemptyset(&G.blocked_set); - already is */
sigprocmask(SIG_SETMASK, NULL, &G.blocked_set);
sig = 0;
while (mask) {
@@ -859,6 +865,7 @@ static void init_signal_mask(void)
}
sigprocmask(SIG_SETMASK, &G.blocked_set, &G.inherited_set);
}
+
static void check_and_run_traps(void)
{
static const struct timespec zero_ts = { 0, 0 };
@@ -910,7 +917,7 @@ static void sigexit(int sig)
#if ENABLE_HUSH_INTERACTIVE
/* Careful: we can end up here after [v]fork. Do not restore
- * tty pgrp, only top-level shell process does that */
+ * tty pgrp then, only top-level shell process does that */
if (G.interactive_fd && getpid() == G.root_pid)
tcsetpgrp(G.interactive_fd, G.saved_tty_pgrp);
#endif
@@ -931,11 +938,11 @@ static void maybe_set_sighandler(int sig)
*/
if (!((G.non_DFL_mask >> sig) & 1)) {
handler = signal(sig, sigexit);
- if (handler == SIG_IGN) /* restore back to IGN! */
+ if (handler == SIG_IGN) /* oops... restore back to IGN! */
signal(sig, handler);
}
}
-/* Used only to set handler to restore pgrp on exit, and to reset it to DFL */
+/* Used only to set handler to restore pgrp on exit */
static void set_fatal_signals_to_sigexit(void)
{
if (HUSH_DEBUG) {