How do you wait for command substitution processes to complete?
When running a command using the >(cmd) syntax in bash how do you wait for the command to complete before moving on in your script?
Here is a simple example:
This produces the output:
My objective is to guarantee echo "WORLD" gets printed after all of the >() processes are done.
The bigger picture is that I have a lot of large log files to process through a variety of log parsers and using this syntax does have the positive effect of reading the files from disk once to process them in parallel in many sub processes taking advantage of multi-core CPUs. Everything works fine except for the fact that I can't tell when those processes are done.
I can think of one solution where I could have my log processing scripts write an "I'm Done" message to a file or pipe somewhere for the parent to loop listening for.
I'm using PERL on windows NT to try to run an extract of data. I have multiple zip files in multiple locations. I am extracting "*.t" from zip files and subsequently adding that file to one zip file so when the script is complete I should have one zip file with a whole bunch of ".t" files in it.
... (2 Replies)
I am attempting within a for-loop, to have my shell script (Solaris v8 ksh) wait until a copy file command to complete before continueing. The specific code is:
for files in $(<inputfile.lst)
do
mv directory/$files directory/$files
ksh -m -i bg %%
wait $!
done
I am shaky on the... (3 Replies)
Does anyone have an example of a korn shell scripts kicking of multiple background processes and then using the wait command to get the return code from those processes?
I want to write a program that kicks off multiple Oracle procedures and then wait for the return code before I procede.... (1 Reply)
As far as I can tell, the bash wait command waits for a logical "AND" of all the child processes.
Assuming I am coding in C:
(1) What is the function I would use to create multiple bash child process running perl?
(2) What is the function I would use to reinvent the bash wait command so I... (4 Replies)
Did not use 'wait' yet.
How I understand by now the wait works only for child processes, started background.
Is there any other way to watch completion of any, not related process (at least, a process, owned by the same user?)
I need to start a background process, witch will be waiting... (2 Replies)
Hi All,
Am finding performance of my SD card using hdparm.
hdparm -tT /dev/BlockDev0
/dev/BlockDev0:
Timing cached reads: 1118 MB in 2.00 seconds = 558.61 MB/sec
HDIO_DRIVE_CMD(null) (wait for flush complete) failed: Inappropriate
ioctl for device
Timing buffered disk reads: 14... (0 Replies)
Hi, Is there any way to know the child process status as and when it finished. If i write like below
nohup sh a1.sh & ### has sleep 20 ;echo a1.sh
nohup sh a2.sh & ### has sleep 10 ;echo a2.sh
nohup sh a3.sh & ### has sleep 5 ;echo a3.sh
wait
This will wait till a1.sh ,a2.sh a3.sh... (0 Replies)
Let's say I start process A.sh, then start process B.sh. I call both of them in my C.sh
How can I make sure that B starts its execution only after A.sh finishes.
I have to do this in loop.Execution time of A.sh may vary everytime.
It is a parameterized script. (17 Replies)
Hi All,
I have a question related to Shell scripting. In my shell script, I have following two commands in sequence:
sed 's/^/grep "^120" /g' $ORIGCHARGEDAMTLIST|sed "s;$;| cut -f$FIELD_NO1 -d '|' | awk '{ sum+=\$1} END {printf (\"%0.2f\\\n\", sum/100)}' >$TEMPFILE
mv $TEMPFILE $ORIGFILE... (3 Replies)
Hello,
im having bash script with
while ***
command1 &&
command2 &&
command3 &&
done
i want to ask how i can prevent overloading server, by waiting untill all commands complete? any low resources intensive command like "wait" - i dont know if exist? (2 Replies)
Discussion started by: postcd
2 Replies
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tcl_detachpids
Tcl_DetachPids(3) Tcl Library Procedures Tcl_DetachPids(3)__________________________________________________________________________________________________________________________________________________NAME
Tcl_DetachPids, Tcl_ReapDetachedProcs, Tcl_WaitPid - manage child processes in background
SYNOPSIS
#include <tcl.h>
Tcl_DetachPids(numPids, pidPtr)
Tcl_ReapDetachedProcs()
Tcl_Pid
Tcl_WaitPid(pid, statusPtr, options)
ARGUMENTS
int numPids (in) Number of process ids contained in the array pointed to by pidPtr.
int *pidPtr (in) Address of array containing numPids process ids.
Tcl_Pid pid (in) The id of the process (pipe) to wait for.
int *statusPtr (out) The result of waiting on a process (pipe). Either 0 or ECHILD.
int options (in) The options controlling the wait. WNOHANG specifies not to wait when checking the process.
_________________________________________________________________DESCRIPTION
Tcl_DetachPids and Tcl_ReapDetachedProcs provide a mechanism for managing subprocesses that are running in background. These procedures
are needed because the parent of a process must eventually invoke the waitpid kernel call (or one of a few other similar kernel calls) to
wait for the child to exit. Until the parent waits for the child, the child's state cannot be completely reclaimed by the system. If a
parent continually creates children and doesn't wait on them, the system's process table will eventually overflow, even if all the children
have exited.
Tcl_DetachPids may be called to ask Tcl to take responsibility for one or more processes whose process ids are contained in the pidPtr
array passed as argument. The caller presumably has started these processes running in background and does not want to have to deal with
them again.
Tcl_ReapDetachedProcs invokes the waitpid kernel call on each of the background processes so that its state can be cleaned up if it has
exited. If the process has not exited yet, Tcl_ReapDetachedProcs does not wait for it to exit; it will check again the next time it is
invoked. Tcl automatically calls Tcl_ReapDetachedProcs each time the exec command is executed, so in most cases it is not necessary for
any code outside of Tcl to invoke Tcl_ReapDetachedProcs. However, if you call Tcl_DetachPids in situations where the exec command may
never get executed, you may wish to call Tcl_ReapDetachedProcs from time to time so that background processes can be cleaned up.
Tcl_WaitPid is a thin wrapper around the facilities provided by the operating system to wait on the end of a spawned process and to check a
whether spawned process is still running. It is used by Tcl_ReapDetachedProcs and the channel system to portably access the operating sys-
tem.
KEYWORDS
background, child, detach, process, wait
TclTcl_DetachPids(3)