03-17-2011
Quote:
Originally Posted by
omega666
The man system says
During execution of the command, SIGCHLD will be blocked, and SIGINT and SIGQUIT will be ignored.
What does this mean?
It means that SIGCHLD signals won't be handled during the time system() is still being processed.
Quote:
And if i am making a function that does what system does how do i write this signal stuff?
You do that with
sigprocmask, which is used to view or modify the set of signals the process is currently blocking or whatever. Change the signals at the beginning and then, right before you return, change them back. See
man sigprocmask.
9 More Discussions You Might Find Interesting
1. IP Networking
Dear all,
If I login to a Unix system (general user account), will the unix system generate a history file?
If positve, will it stored the IP adress also?
Thanks and Regards
Penny Li
;) (2 Replies)
Discussion started by: PennyLi
2 Replies
2. UNIX for Dummies Questions & Answers
Hello all,
I'm ufs file system, how can u use the same disk in another machine with the data in tact? to make it clear, I've an ufs FS in a mount point /file1 ( 8GB). now they decide to reintall the OS. After the reinstall, how can i get the same data as it is? will mounting the disk as /file1... (3 Replies)
Discussion started by: i2admin
3 Replies
3. Programming
Hello all !
Could someone throw some light on whether there's a limit to the number of characters contained in the command string that is passed to the system() call in C.
Is it OS dependent? If yes, what are the limits for each?
Thanks. (4 Replies)
Discussion started by: vsanjit
4 Replies
4. Solaris
Hello,
I have few questions about file system in Unix and Linux.
1. What's the difference between Unix and Linux in their file system? Are they the same?
2. Is in Unix directory for administrator "/root" - like in Linux - Ubuntu or not?
3.Where is the users directory in Unix? Is it... (2 Replies)
Discussion started by: niki22
2 Replies
5. Programming
in man system it talks about SIGCHLD will be blocked, and SIGINT and SIGQUIT will be ignored.
Does this signal stuff also happen in popen command?
(even though man popen says nothing about signals)
also if I am not using wait(&status) and I am using waitpid(pid, NULL, 0)
how would... (1 Reply)
Discussion started by: omega666
1 Replies
6. Shell Programming and Scripting
Hi
I have created a perl script & running it using Linux machine. I want my script to die when system command is unsuccessful but script is dying even when system command gets executed successfully. :wall:
I am using the command below :-
system($cmd) || die "FAILED $!";
print "Hello";
... (2 Replies)
Discussion started by: Priyanka Gupta
2 Replies
7. UNIX for Dummies Questions & Answers
I'm currently studying for my exam, and is practicing with sample exam questions.
However there is a question asking "Name THREE UNIX Directory system calls" and the answer given is "opendir, closedir and readdir", however the next question ask "Why is a write directory system call not included... (1 Reply)
Discussion started by: Izzy123
1 Replies
8. UNIX for Dummies Questions & Answers
Hi,
The file system unix use a multilevel indexes access to disk, 12 direct blocks, 1 single indirect block, 1 double indirect block, 1 triple indirect block:
Assuming a:
block = 512 bytes,
pointer = 4 byte,
and there is a file of 200 blocks,
how many disk access is needed to read the block... (1 Reply)
Discussion started by: blob84
1 Replies
9. UNIX for Dummies Questions & Answers
Hi,
I am on Solaris 10 server which is running Veritas. It's E420 server with two drives. I don't know much about Veritas. The other guy who works on this, on vacation this week. :-) Any way, looks like I have hard drive issue on the server.
When I do iostat -E. I see this.
sd0... (4 Replies)
Discussion started by: samnyc
4 Replies
LEARN ABOUT CENTOS
rt_sigprocmask
SIGPROCMASK(2) Linux Programmer's Manual SIGPROCMASK(2)
NAME
sigprocmask - examine and change blocked signals
SYNOPSIS
#include <signal.h>
int sigprocmask(int how, const sigset_t *set, sigset_t *oldset);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
sigprocmask(): _POSIX_C_SOURCE >= 1 || _XOPEN_SOURCE || _POSIX_SOURCE
DESCRIPTION
sigprocmask() is used to fetch and/or change the signal mask of the calling thread. The signal mask is the set of signals whose delivery
is currently blocked for the caller (see also signal(7) for more details).
The behavior of the call is dependent on the value of how, as follows.
SIG_BLOCK
The set of blocked signals is the union of the current set and the set argument.
SIG_UNBLOCK
The signals in set are removed from the current set of blocked signals. It is permissible to attempt to unblock a signal which is
not blocked.
SIG_SETMASK
The set of blocked signals is set to the argument set.
If oldset is non-NULL, the previous value of the signal mask is stored in oldset.
If set is NULL, then the signal mask is unchanged (i.e., how is ignored), but the current value of the signal mask is nevertheless returned
in oldset (if it is not NULL).
The use of sigprocmask() is unspecified in a multithreaded process; see pthread_sigmask(3).
RETURN VALUE
sigprocmask() returns 0 on success and -1 on error. In the event of an error, errno is set to indicate the cause.
ERRORS
EFAULT the set or oldset argument points outside the process's allocated address space.
EINVAL The value specified in how was invalid.
CONFORMING TO
POSIX.1-2001.
NOTES
It is not possible to block SIGKILL or SIGSTOP. Attempts to do so are silently ignored.
Each of the threads in a process has its own signal mask.
A child created via fork(2) inherits a copy of its parent's signal mask; the signal mask is preserved across execve(2).
If SIGBUS, SIGFPE, SIGILL, or SIGSEGV are generated while they are blocked, the result is undefined, unless the signal was generated by
kill(2), sigqueue(3), or raise(3).
See sigsetops(3) for details on manipulating signal sets.
SEE ALSO
kill(2), pause(2), sigaction(2), signal(2), sigpending(2), sigsuspend(2), pthread_sigmask(3), sigqueue(3), sigsetops(3), signal(7)
COLOPHON
This page is part of release 3.53 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/.
Linux 2013-04-19 SIGPROCMASK(2)