7b830e78f
Denis Vlasenko
2009-03-31
Subject
hush: fix comments, no code changes
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shell/hush.c+36 -29
| @@ -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) { | |