Re: shell and output redirection
- From: Mladen Gogala <mladen@xxxxxxxxxxxxxxx>
- To: oracle-l@xxxxxxxxxxxxx
- Date: Fri, 2 Jul 2004 15:24:29 -0400
On 07/02/2004 02:57:21 PM, Ganesh.Raja@xxxxxxxxxxxxxxxxxxx wrote:
> They are Not Run ||'el... The utput of the first program is stored before
> the second is executed...
Not true. Here is the trace:
read(0, "l", 1) = 1
write(2, "l", 1) = 1
rt_sigprocmask(SIG_BLOCK, NULL, [RTMIN], 8) = 0
read(0, "s", 1) = 1
write(2, "s", 1) = 1
rt_sigprocmask(SIG_BLOCK, NULL, [RTMIN], 8) = 0
read(0, "|", 1) = 1
write(2, "|", 1) = 1
rt_sigprocmask(SIG_BLOCK, NULL, [RTMIN], 8) = 0
read(0, "s", 1) = 1
write(2, "s", 1) = 1
rt_sigprocmask(SIG_BLOCK, NULL, [RTMIN], 8) = 0
read(0, "o", 1) = 1
write(2, "o", 1) = 1
rt_sigprocmask(SIG_BLOCK, NULL, [RTMIN], 8) = 0
read(0, "e", 1) = 1
write(2, "e", 1) = 1
rt_sigprocmask(SIG_BLOCK, NULL, [RTMIN], 8) = 0
read(0, "\10", 1) = 1
write(2, "\10 \10", 3) = 3
rt_sigprocmask(SIG_BLOCK, NULL, [RTMIN], 8) = 0
read(0, "e", 1) = 1
write(2, "e", 1) = 1
rt_sigprocmask(SIG_BLOCK, NULL, [RTMIN], 8) = 0
read(0, "\10", 1) = 1
write(2, "\10 \10", 3) = 3
rt_sigprocmask(SIG_BLOCK, NULL, [RTMIN], 8) = 0
read(0, "r", 1) = 1
rt_sigprocmask(SIG_BLOCK, ~[], [RTMIN], 8) = 0
rt_sigprocmask(SIG_SETMASK, [RTMIN], NULL, 8) = 0
write(2, "r", 1) = 1
rt_sigprocmask(SIG_BLOCK, NULL, [RTMIN], 8) = 0
read(0, "t", 1) = 1
write(2, "t", 1) = 1
rt_sigprocmask(SIG_BLOCK, NULL, [RTMIN], 8) = 0
read(0, "\r", 1) = 1
write(2, "\n", 1) = 1
/* Read "ls|sort" from terminal screen */
pipe([3, 4]) = 0
rt_sigprocmask(SIG_BLOCK, [INT CHLD], [CHLD RTMIN], 8) = 0
pipe([5, 6]) = 0
fork() = 9430
setpgid(9430, 9430) = 0
rt_sigprocmask(SIG_SETMASK, [CHLD RTMIN], NULL, 8) = 0
close(4) = 0
close(4) = -1 EBADF (Bad file descriptor)
rt_sigprocmask(SIG_BLOCK, [INT CHLD], [CHLD RTMIN], 8) = 0
fork() = 9431
/* Create two pipes and fork two processes */
wait4(-1, [WIFEXITED(s) && WEXITSTATUS(s) == 0], 0, NULL) = 9429
/* Wait for the output. Exec calls in the 2 forked processes weren't visible */
--
Mladen Gogala
Oracle DBA
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