09-28-2010
here's an example of what im talking about.
myshell> ls -a
. .. a.out fork.c Hello .hi shell shell.c
myshell> ls -l
total 36
-rwxr-xr-x 1 matt matt 8435 2010-09-26 20:43 a.out
-rw-r--r-- 1 matt matt 943 2010-09-26 20:44 fork.c
drwxr-xr-x 2 matt matt 4096 2010-09-27 02:13 Hello
-rwxr-xr-x 1 matt matt 8322 2010-09-28 16:21 shell
-rw-r--r-- 1 matt matt 1693 2010-09-28 16:21 shell.c
myshell> ls &
myshell> a.out fork.c Hello shell shell.c
ls -a
myshell> . .. a.out fork.c Hello .hi shell shell.c
<---- here is where the "pointer" ends up. i can still type commands, but it doesn't show "myshell>" anymore
I tried the fprintf(stderr, "hello world\n"); thing. but it didn't work, it only happens when the & happens for some reason...
Looking at my code it should go like this.
parse arg. which prints out myshell>
User inputs commands<---
parse arg parses it.
so we have myshell> ls -l
so we execute it. which goes on a newline (apparently) (since BG is 0) and we wait for it to finish.
we then go back in the loop and myshell is printed again.
But with &....it goes back to parse arg (since we can still type things in, and they work) but myshell> isn't printed....which makes zero sense. Im looking at my code, tracing through....and I just dont see why this is happening, even when we aren't "waiting" the the process to finish, it should still loop back around to the parsearg function which has the myshell> printout.
It seems like typing in the & for SOME reason....like...screws all my printouts up.
edit: I think I may know why now.....im not resetting the BG bool to false, so it's treating them all as "background" processes i think........
edit2: CRAP nevermind, i realize im never setting BG permanently, oh well there goes that theory.
Last edited by Mercfh; 09-28-2010 at 06:34 PM..
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SLEEP(1) BSD General Commands Manual SLEEP(1)
NAME
sleep -- suspend execution for an interval of time
SYNOPSIS
sleep seconds
DESCRIPTION
The sleep utility suspends execution for a minimum of seconds. It is usually used to schedule the execution of other commands (see EXAMPLES
below).
Note: The NetBSD sleep command will accept and honor a non-integer number of specified seconds. This is a non-portable extension, and its
use will nearly guarantee that a shell script will not execute properly on another system.
When the SIGINFO signal is received, the estimate of the amount of seconds left to sleep is printed on the standard output.
EXIT STATUS
The sleep utility exits with one of the following values:
0 On successful completion, or if the signal SIGALRM was received.
>0 An error occurred.
EXAMPLES
To schedule the execution of a command for 1800 seconds later:
(sleep 1800; sh command_file >& errors)&
This incantation would wait half an hour before running the script command_file. (See the at(1) utility.)
To reiteratively run a command (with csh(1)):
while (1)
if (! -r zzz.rawdata) then
sleep 300
else
foreach i (*.rawdata)
sleep 70
awk -f collapse_data $i >> results
end
break
endif
end
The scenario for a script such as this might be: a program currently running is taking longer than expected to process a series of files, and
it would be nice to have another program start processing the files created by the first program as soon as it is finished (when zzz.rawdata
is created). The script checks every five minutes for the file zzz.rawdata, when the file is found, then another portion processing is done
courteously by sleeping for 70 seconds in between each awk job.
SEE ALSO
at(1), nanosleep(2), sleep(3)
STANDARDS
The sleep command is expected to be IEEE Std 1003.2 (``POSIX.2'') compatible.
BSD
August 13, 2011 BSD