Okay -- but I still don't get why the message isn't displayed. Other folks can get it.
No they don't, not when their shell's not the foreground process.
Quote:
Any idea why not me?
When you're running an external command, your shell isn't the foreground process, so the signal doesn't get delivered to it. It gets delivered to the foreground process instead, in this case, sleep, which causes it to quit and return a non-zero error code:
This is because the process isn't actually killed by the shell -- it's killed directly, by you. The terminal device translates control-C directly into SIGINT for you. What the 'foreground process' is isn't a property of the shell, either -- it's a property of the terminal itself, so it always knows where to send SIGINT direct.
Quote:
My book says it should display the message and go right back to the loop.
This is true only if your shell is the foreground process. If it's in the middle of running any externals, your shell's not in the foreground.
Last edited by Corona688; 07-06-2011 at 09:10 PM..
I'm using the trap command to capture any signals received whilst my script is running.
How's the best way of writing the signal and any other error messages to a file/error log' without having to type '2>$1' on the command line after the script name?
Cheers (3 Replies)
i have the following script that displays the current time until the user presses CTR + c.... but it does not work properly....
Something is not right with the trap command...
Help plz... :confused:
# script to continuously display current time.
# if script is terminated trap signal... (3 Replies)
Dear All
could you please explain me what does the trap command do and how I can write a program which can work as a trap command(in C Language). (1 Reply)
Could anybody tell me what the trap command does and how it performs the action it does. I had read the trap manual page but it is too concise that nothing is clear about it. Please tell how it works. (1 Reply)
Hi,
I would like to know the use of TRAP command. I am very new to the UNIX environment. I have just started learning the basic. So please teach me in a very simple way to understand.
Also i would like to know the use of following command:
trap 'dialog --msgbox "Script Aborted1" 6 50 ;... (2 Replies)
Hi folks,
I have tried to add some trap detection in the below script....this script is used to monitor database activities...in a rather awkward way :rolleyes:....
The idea behind adding trap is that....this script creates lots of temporary files in the running folder to store the count... (1 Reply)
Hello experts!
I need to know the use of trap command please
In one of our program we have trap "rm -f temp1 ; exit 1" 1 2 15 0
and program always exit with 1
there is a rm -f temp1 as well at the end of the program
as
rm -f temp1
exit 0
when I test a probram with set... (4 Replies)
dear all;
I can't under stand what does "trap" command do:
for example see below:
trap "echo; echo no interrupts >&2; sleep 3" 2 3 15
Plz , can any body explain the action of this command?
BR (3 Replies)
Use and complete the template provided. The entire template must be completed. If you don't, your post may be deleted!
1. The problem statement, all variables and given/known data:
That is the last reply I received from my instructor, and I'm looking for some alternatives.
When using... (2 Replies)
Hi Folks -
For some reason, my trap command is not working. It's placed just prior to a normal exit:
#:: ------------------------------------------------------------------------
#::-- Script Name: LCM_Backup.sh
#::
#::-- Description: This script leverages Utility.sh to perform LCM... (16 Replies)
Discussion started by: SIMMS7400
16 Replies
LEARN ABOUT DEBIAN
tcsetpgrp
TCGETPGRP(3) Linux Programmer's Manual TCGETPGRP(3)NAME
tcgetpgrp, tcsetpgrp - get and set terminal foreground process group
SYNOPSIS
#include <unistd.h>
pid_t tcgetpgrp(int fd);
int tcsetpgrp(int fd, pid_t pgrp);
DESCRIPTION
The function tcgetpgrp() returns the process group ID of the foreground process group on the terminal associated to fd, which must be the
controlling terminal of the calling process.
The function tcsetpgrp() makes the process group with process group ID pgrp the foreground process group on the terminal associated to fd,
which must be the controlling terminal of the calling process, and still be associated with its session. Moreover, pgrp must be a
(nonempty) process group belonging to the same session as the calling process.
If tcsetpgrp() is called by a member of a background process group in its session, and the calling process is not blocking or ignoring
SIGTTOU, a SIGTTOU signal is sent to all members of this background process group.
RETURN VALUE
When fd refers to the controlling terminal of the calling process, the function tcgetpgrp() will return the foreground process group ID of
that terminal if there is one, and some value larger than 1 that is not presently a process group ID otherwise. When fd does not refer to
the controlling terminal of the calling process, -1 is returned, and errno is set appropriately.
When successful, tcsetpgrp() returns 0. Otherwise, it returns -1, and errno is set appropriately.
ERRORS
EBADF fd is not a valid file descriptor.
EINVAL pgrp has an unsupported value.
ENOTTY The calling process does not have a controlling terminal, or it has one but it is not described by fd, or, for tcsetpgrp(), this
controlling terminal is no longer associated with the session of the calling process.
EPERM pgrp has a supported value, but is not the process group ID of a process in the same session as the calling process.
CONFORMING TO
POSIX.1-2001.
NOTES
These functions are implemented via the TIOCGPGRP and TIOCSPGRP ioctls.
History
The ioctls appeared in 4.2BSD. The functions are POSIX inventions.
SEE ALSO setpgid(2), setsid(2), credentials(7)COLOPHON
This page is part of release 3.44 of the Linux man-pages project. A description of the project, and information about reporting bugs, can
be found at http://www.kernel.org/doc/man-pages/.
GNU 2003-01-28 TCGETPGRP(3)