Programming :: [C++] Cannot Catch SIGPIPE Signal?
Mar 27, 2011
I have a Socket library, written in C++, in which the method used to send data never has the opportunity to handle an errno of SIGPIPE. Thus I thought perhaps I should setup a signal handler to receive the signal, but this too is not being called.Is there something that I am missing or doing that is completely wrong? Below is the relevant code. Note that a SIGPIPE signal is generated when the Server is unable to send data to the Client (e.g. the client has terminated).Server code:
Code:
#include <TCPServerSocket.hpp>
#include <string>
[code]...
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Apr 25, 2011
But unable to catch the SIGTERM signal if I do shutdown, as man pages says shutdown genrates the SIGTERM and SIGKILL signals, but we cant handle the SIGKILL signal. My code is working fine if I genrate the SIGTERM signal by Kill command, and also for SIGINT signgal genrated from the CTRL+c key.
Here is my code:
/* Example of using sigaction() to setup a signal handler with 3 arguments
* including siginfo_t.
*/
#include <stdio.h>
#include <unistd.h>
#include <signal.h>
#include <string.h>
[Code]...
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Feb 3, 2010
i write one program,which can dynamiclly be configure by user,using signal SIGHUP.if i start the program in console,it can works well.i.e,i send HUP signal to the process,it can be catched and load the configure file.but,if the program is started from init shell script,in this way,the ppid of the program is 1,the process can not catch the HUP signal but other signal ,such as USR1,can be catched.i don't know if i express clearly.i am not family with shell script.i don't know if it dues to starting from shell script
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Jul 27, 2011
I'm studying an OS programming book, in particular network sockets. I have two questions(2nd one is down at the bottom). There is something I don't quite understand. What if this piece of code, which sets sigpipe's default action to ignore and opens a socket:
Code:
if ((u_ignore_sigpipe() != 0) || ((sock = socket(AF_INET, SOCK_STREAM, 0)) == -1))
return -1;
[code]....
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Mar 2, 2011
I've written a simple server in linux used fork to create a FIFO pipe.The server create two FIFO pipe.One for server read data from client and write data to client.Then another pipe for client read data from server and write data to server.When the server read data from a client used server-pipe and then write data to client.But ,if the client no read open the pipe,the server side write will be crashed because of a broken-pipe SIGPIPE. How to check whether the read side is opened?Or,how to catch the SIGPIPE,and then my server will still execute on,not crashed!!
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Feb 2, 2011
right now i am writing bash script for simple everyday todo tasks.script consisit of two files, fisrt is just script (which can delete/append /clear) and second one is todolist.txt which stores my notes.I am litlebit confused about sed!!for example, If my todolist.txt have these lines:
- Writing my Homework
- take my girlfriend to launch
- Take a break
How can sed take my input $@ and delete all line with name "Homework"..i trayed with many sed combination like:
Code:
sed s/$@//g
sed 'd/$@/'
and many more combination with ""/'' or bracket but nothing helped
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Jan 26, 2009
I want to catch some outputs in two different log files in bash, file simple.log and all.log So far, the script is started like this:
Code:
xterm -e "(./myscript.sh | tee -a simple.log) >& all.log"
What I want is:
- In simple.log, I want all the stdout but WITHOUT errors.
- In all.log I want BOTH stdout and stderr.
So all is ok, and the output becomes:
all.log
Code:
starting copying files
mv: cannot move ... : permission denied
copying completed
simple log
Code:
starting copying files
copying completed
But, in the new xterm, I'm loosing stdout. There is no output.How can I have the files logged as they are but also have the stdout in the xterm.
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Jan 24, 2011
The following C++ program doesn't catch the exception:
Code:
#include <iostream>
using namespace std;
[code]...
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Oct 30, 2010
How do you catch user input while the script is running? Or, how would you make two scripts run at the same time, but use input from one script to the other? The program I'm trying to make, echos text on the screen continuously, but while thats happening, I want the user to be able to input something, so the program can detect the input and display something else. So I thought maybe I could make two scripts run to do each task.
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Apr 21, 2010
I have the following working script. It checks the directory for txt files, if files are there, it copies to another directory or gives error. I would like to exclude "file not found" errors and send them to /dev/null. All other errors should go to the email address as usual.
Code:
#!/bin/bash
function err
{
if [[ $? -ne 0 ]]
[Code]....
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Feb 9, 2011
I want that I click with the mouse on the video, it paused.I notice that there is "BaconVideoWidget" which I guess is the video rendering widget but it don't have signal named "clicked":
Code:
vd = totem_object.get_video_widget()
vd.connect("clicked", vd.hide)
[code]....
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Oct 22, 2010
I'm doing the shell history audit logging using syslog to gather the command history. I'm using this well publicized method using trap and logger:
declare -r REAL_LOGNAME=`/usr/bin/who am i | cut -d" " -f1`
function log2syslog {
declare command
command=`fc -ln -0`
logger -p local1.notice -t bash -i ": $REAL_LOGNAME as $LOGNAME :$command"
}
trap log2syslog DEBUG TERM
The problem is that the trap on DEBUG will catch the next to last command executed (by virtue of the "fc" command) which is not the current command executed. TERM will catch that "next to last" command on exit, thus completing the logging of each command executed during that session.
However, CTL+D doesn't seem to emit a SIGTERM signal. What signal is actually being emitted and can it be trapped? I guess another question would be whether there is a way to trap history after command line execution? Moving to Bash 4.1 isn't possible in our "supported" multi-platform environment
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Mar 12, 2011
I have created a pthread, and installed a signal handler inside that, same way as we do in main( ) function. The thread's signal handler is a separate function. Surprisingly, it is not working, that is the thread's signal handler is not able to catch signals. Here is the code:
Code: #include <unistd.h>
#include <sys/types.h>
#include <stdio.h>
#include <signal.h>
typedef struct data
[Code]...
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Nov 1, 2010
Is it possible to connect a signal handler to a variable?So when the variable changes the signal handler is called.I have a vector containing strings which i want to parse when there are one or more available strings in the vector
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Apr 27, 2011
I have a signal handler in my tool, which is registered and used between some particular interval (i am using timer). Now this signal handler should NOT allow any other handler to be registered or invoked after this handler is once registered. Is there any way to accomplish this?
[code]...
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Jan 15, 2010
I am writing a bash script where I need standard Input should be saved in a file and should be terminated by passing CTRL+D signal. Any clue how can I do that in bash script.
e.g.
Enter one line at a time
Press CTRL+D to finish
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Mar 4, 2010
I was trying to program using fork(). The objective of this code is to
1. I am activating a process A - SubSuctionMotors.
2. Process A is going to stop with either of this condition
a) Switch is activated - swret=1
b) Time allowed has expired
3. Stop the process A.
[Code]...
1. We purposely force the switch to be inactive to test the child process (timer), whether after 2 seconds the motor stop. It turns out to be successful in first few attempts. After some while, the program hang, nothing is executed anymore and the program is not exit or terminated. What can cause the program to hang?
2. We tried to stop motor by switch activation (if the switch is to be successfully activated, the time it takes will always be shorter than the timer allowed time). However, the program did not seems like noticing the switch has been activated, and it just stop the motor according to timer. Why it behave this way?
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Jun 16, 2010
#!/bin/sh
trap "echo Haha" SIGUSER1
echo "asit"
count=1
while [ $count -le 10 ]
do
echo "Loop #$count"
sleep 10
count=$[ $count + 1 ]
done
echo "This is the end"
Why this is showing following error?
trap: 3: SIGUSER1: bad trap
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May 21, 2010
I'm just beginning to program with GTK+, and I'm facing this issue: I want to inhibit a signal emission inside one and only one function. I've down cut my code into the smallest example I can to show you what I want to do:The "Emitter" contains a "GtkSpinBox" and it relays the "value-changed" signal, it's header:
Code:
#ifndef EMITTER_H
#define EMITTER_H
[code]....
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Jan 14, 2015
Basically I'm intending to write serial RX signal handler.Application receives defined packages of data over serial which contains header and payload. Handler should analyse incoming stream and upon detection of header (header is 6B in length) switches to receive payload of length defined in header, then after receiving full message packs it and sends to application for handling.Problem I'm facing is that at random moments in signal I receive errors that "Resource temporarily unavailable" while reading from ttyOx device and I see that sometimes I miss incoming data.Also is it possible that if while I'm handling signal one more signal arrives and it is started to be handled parallel? If it is, what are the ways to prevent it? So I would be sure that no more signals will fire on same peripheral until I will finish handling what I have on my hands now.
Serial open and init:
Code: Select allint open_port(int port_nr) {
int fd; /* File descriptor for the port */
switch (port_nr) {
case 1:
fd = open("/dev/ttyO1", O_RDWR | O_NOCTTY | O_NDELAY);
break;
[code]....
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Jul 4, 2011
I'm learning Signals, and I have a question:
Is possible to make a handle when I press any of the keyboard buttons?
The SIGINT handles the Ctrl-C combination, but I want to handle if any keyboard button was pressed.
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Feb 15, 2010
locking mutex (phtread_t type) in a signal handler function (installed by function signal()) for Linux. It seems that if the mutex has been previously locked by another thread outside the signal handler function and then the signal handler function tries to lock it, the whole process hangs.
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Jan 20, 2010
I'm new to Unix and every signal handler algorithm I've seen is more or less a copy of what I'm trying to do.[URL] designing a signal handler with sigwait in UNIX?
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Mar 16, 2011
I have a problem with the last point of some homework I have for an OS class. I need the program to print the pid upon execution, then for 10 seconds react to SIGUSR1, SIGUSR2 and SIGTERM. If either USR1 or USR2 is received, the 10 seconds are reset. Some of the functions I'm told to use are alarm(), pause() and signal(). The nicest way I found was to handle SIGUSR1, SIGUSR2 and SIGALRM in the parent process, with SIGALRM killing the child (with a SIGTERM). In the child a pause() (or for(; pause() would be enough for it to be alive until killed from the SIGALRM handler in the parent.
What I found is that I can't just do a wait() in the parent process, waiting for the child to be killed, since whenever the parent receives a SIGUSR1 or SIGUSR2, the right handler is called but the child exits nicely. I tried blocking/ignoring those signals in the child, since the default behaviour for SIGUSR1 and SIGUSR2 is to terminate the process, but the result is the same. The only way I could do it is using a waitpid() within a do { } while(!WIFSIGNALED(status)) since when the child gets killed with the parent's kill(), it's WIFSIGNALED, whereas when it exits after the parent handles a SIGUSR1/2, it's WIFEXITED.
P.S. What I'm doing to achieve the expected 10s window is calling alarm(10) in the parent process and again within the SIGUSR1/2 handlers. In the SIGALRM handler I kill the child and within the child I simply do a for(; pause()
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Nov 4, 2010
I am using an imx27 and have a timer set up for 100 ms and a loop to count the pulses while the timer has not expired. I get about 90 % reliable results but every once in a while i get one that is out to lunch. I am reading in a signal that is about 500khz and counting on an transition. I usually get around 85k count. But i will randomly get a 50k count.
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Jun 14, 2011
In a single main() function,so need signal handling. Use Posix Message Queue IPC mechanism , can ignore the priority and other linked list message,to implement the scenario:
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Jun 17, 2010
I would like to make a shell script that will do the following :- have a web-page using curl- download a picture from the web-page- have a line in the source code of the web page
- catch a string (a link patch) from the line- go to another page of the website from the result of the previous step- repeat all this until there is no match for step 3I know how to :- have the web-page source code using curl (simple, we just have to make "curl- download the picture (as simple as the first step)- have a line in the source code (grep is made for that, isn't it ?)- go to another website from the result of the previous step (it's the same as the first step)But I really don't know how I can do the fourth step of my script.
In facts, I don't know regular expressions and even the shell command that can help me to do this.To be more clear, I would like to store in a variable the string represented by the star (*) in this : <a href="*">Next ></a>
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May 23, 2011
I have a doubt about signals in C programming. I have done this little program to explain it. It creates a child process with fork and, when the child ends, receives the SIGCHLD signal and wait for its termination.Ok, quite easy, BUT when I execute this code the SIGCHLD signal is received twice, first as an error (returns -1) and the second one to finish the child process.I don't understand the meaning of the first received signal. Why is it generated? Is the code wrong? (if you add the SIGINT and press Ctrl+C during the execution it also receives two signals instead of one)
Code: #include <stdio.h>
#include <unistd.h>
#include <string.h>
[code]....
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Nov 26, 2008
I tried googling but didn't get any answer for this.I have a process called "abc" and it is running with PID "123".I have a putty session opened with PID "999".I am giving kill -TERM 123 from putty session.My process "abc" before dying it should catch the PID of the terminal which provided TERM signal to it.Is there any way to find this out
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Jul 21, 2011
I have the following requirement in my module. The driver gets some data from the external device. After getting 1MB of data it has to send it to the user space application. What is the best thing to implement for this in driver.? Is it ok to implement like, after getting data, the driver will send a signal to the user space application. Then the user space application sends an ioctl to read the data. Is there any alternate, that the driver directly sends the data without the user space application asks for it.?
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