fork and exec. fork() copies your process but returns a different value to the copy so it can take a new direction. exec() replaces it with a different program. the original program can do other things and/or wait for the child to complete. see man fork, man execv, man wait.
Hi
I have a doubt in the way the variables inside a function are treated .
if a function is called from the main script directly, the variables inside them act as global variables.
however if the return value of the function is stored to some other variable in the main script as shown,... (3 Replies)
Hi all,
I'm doing automation task for my team and I just started to learn unix scripting so please shed some light on how to do this:
1) I have 2 sets of datafiles - datafile A and B. These datafiles must be loaded subsequently and cannot be loaded concurrently.
2) So I loaded datafile A... (10 Replies)
I have write a shell function to get the maximum of a vector.
However, the returned value from the function is not always
the correct one.
Here is the script:
maxval()
{
local max j i size arrval
size=$1 ; shift
max=-999999999
i=0
while
do
arrval="$1"
if
then
... (5 Replies)
What I need to learn is how to use a script that launches background processes, and then kills those processes as needed.
The script successfully launches the script. But how do I check to see if the job exists before I kill it?
I know my problem is mostly failure to understand parameter... (4 Replies)
Hi,
I have created a function f1 defined in script A.sh .I have called this function in background . But I want to use its return value for another function f2 in script A.sh.
I tried declaring it as a global variable, yet it always returns the status as 0. Is there any way with which I can get... (7 Replies)
Not sure where the problem is. I can run the script without any issue using the following command.
. /opt/app/scripts/cdc_migration.sh
But it fails with the below error when I try it this way
/opt/app/scripts/cdc_migration.sh
/opt/app/scripts/cdc_migration.sh: line 65: return: can only... (1 Reply)
Hi All,
Good Day, seeking for your assistance on how to not perform my 2nd, 3rd,4th etc.. function if my 1st function is in else condition.
#Body
function1()
{
if
then
echo "exist"
else
echo "not exist"
}
#if not exist in function1 my all other function will not proceed.... (4 Replies)
Discussion started by: meister29
4 Replies
LEARN ABOUT PLAN9
wait
WAIT(2) System Calls Manual WAIT(2)NAME
wait - wait for a process to exit
SYNOPSIS
#include <u.h>
#include <libc.h>
int wait(Waitmsg *w)
DESCRIPTION
Wait causes a process to wait for any child process (see fork(2)) to exit. It returns the pid of a child that has exited and fills in w
with more information about the child. W points to a Waitmsg, which has this structure:
typedef
struct Waitmsg
{
char pid[12]; /* of loved one */
char time[3*12]; /* of loved one & descendants */
char msg[ERRLEN];
} Waitmsg;
Pid is the child's process id. The time array contains the time the child and its descendants spent in user code, the time spent in system
calls, and the child's elapsed real time, all in units of milliseconds. All integers in a Waitmsg are formatted as right-justified textual
numbers in 11-byte fields followed by a blank. Msg contains the message that the child specified in exits(2). For a normal exit, msg[0]
is zero, otherwise msg is prefixed by the process name, a blank, the process id, and a colon.
If there are no more children to wait for, wait returns immediately, with return value -1.
SOURCE
/sys/src/libc/9syscall
SEE ALSO fork(2), exits(2), the wait file in proc(3)DIAGNOSTICS
Sets errstr.
WAIT(2)