ash: add "wait -n" bashism

function                                             old     new   delta
waitcmd                                              205     288     +83
dowait                                               405     444     +39
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 2/0 up/down: 122/0)             Total: 122 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 47 insertions, 6 deletions

diff --git a/shell/ash.c b/shell/ash.c
index a4394d756..b1499b037 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -3522,7 +3522,7 @@ struct procstat {
 
 struct job {
         struct procstat ps0;    /* status of process */
-        struct procstat *ps;    /* status or processes when more than one */
+        struct procstat *ps;    /* status of processes when more than one */
 #if JOBS
         int stopstatus;         /* status of a stopped job */
 #endif
@@ -4235,6 +4235,9 @@ wait_block_or_sig(int *status)
 #define DOWAIT_NONBLOCK 0
 #define DOWAIT_BLOCK    1
 #define DOWAIT_BLOCK_OR_SIG 2
+#if ENABLE_ASH_BASH_COMPAT
+# define DOWAIT_JOBSTATUS 0x10   /* OR this to get job's exitstatus instead of pid */
+#endif
 
 static int
 dowait(int block, struct job *job)
@@ -4242,7 +4245,11 @@ dowait(int block, struct job *job)
         int pid;
         int status;
         struct job *jp;
-        struct job *thisjob = NULL;
+        struct job *thisjob;
+#if ENABLE_ASH_BASH_COMPAT
+        bool want_jobexitstatus = (block & DOWAIT_JOBSTATUS);
+        block = (block & ~DOWAIT_JOBSTATUS);
+#endif
 
         TRACE(("dowait(0x%x) called\n", block));
 
@@ -4279,10 +4286,10 @@ dowait(int block, struct job *job)
         }
         TRACE(("wait returns pid=%d, status=0x%x, errno=%d(%s)\n",
                                 pid, status, errno, strerror(errno)));
+        thisjob = NULL;
         if (pid <= 0)
                 goto out;
 
-        thisjob = NULL;
         for (jp = curjob; jp; jp = jp->prev_job) {
                 int jobstate;
                 struct procstat *ps;
@@ -4341,6 +4348,13 @@ dowait(int block, struct job *job)
  out:
         INT_ON;
 
+#if ENABLE_ASH_BASH_COMPAT
+        if (want_jobexitstatus) {
+                pid = -1;
+                if (thisjob && thisjob->state == JOBDONE)
+                        pid = thisjob->ps[thisjob->nprocs - 1].ps_status;
+        }
+#endif
         if (thisjob && thisjob == job) {
                 char s[48 + 1];
                 int len;
@@ -4523,15 +4537,24 @@ waitcmd(int argc UNUSED_PARAM, char **argv)
         struct job *job;
         int retval;
         struct job *jp;
-
+#if ENABLE_ASH_BASH_COMPAT
+        int status;
+        char one = nextopt("n");
+#else
         nextopt(nullstr);
+#endif
         retval = 0;
 
         argv = argptr;
-        if (!*argv) {
-                /* wait for all jobs */
+        if (!argv[0]) {
+                /* wait for all jobs / one job if -n */
                 for (;;) {
                         jp = curjob;
+#if ENABLE_ASH_BASH_COMPAT
+                        if (one && !jp)
+                                /* exitcode of "wait -n" with nothing to wait for is 127, not 0 */
+                                retval = 127;
+#endif
                         while (1) {
                                 if (!jp) /* no running procs */
                                         goto ret;
@@ -4547,13 +4570,31 @@ waitcmd(int argc UNUSED_PARAM, char **argv)
          * with an exit status greater than 128, immediately after which
          * the trap is executed."
          */
+#if ENABLE_ASH_BASH_COMPAT
+                        status = dowait(DOWAIT_BLOCK_OR_SIG | DOWAIT_JOBSTATUS, NULL);
+#else
                         dowait(DOWAIT_BLOCK_OR_SIG, NULL);
+#endif
         /* if child sends us a signal *and immediately exits*,
          * dowait() returns pid > 0. Check this case,
          * not "if (dowait() < 0)"!
          */
                         if (pending_sig)
                                 goto sigout;
+#if ENABLE_ASH_BASH_COMPAT
+                        if (one) {
+                                /* wait -n waits for one _job_, not one _process_.
+                                 *  date; sleep 3 & sleep 2 | sleep 1 & wait -n; date
+                                 * should wait for 2 seconds. Not 1 or 3.
+                                 */
+                                if (status != -1 && !WIFSTOPPED(status)) {
+                                        retval = WEXITSTATUS(status);
+                                        if (WIFSIGNALED(status))
+                                                retval = WTERMSIG(status) + 128;
+                                        goto ret;
+                                }
+                        }
+#endif
                 }
         }