Programming :: C - System Call & Error Checking?
Sep 18, 2010
I am trying to figure out how i would go about finding out where system call is made and error checking is not done. I have code below, if somebody can point me in the right direction where system call is made but error checking is not done.Quote:
#include "shell.h"
#include <stdio.h>
#include <string.h>
[code]....
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Aug 1, 2010
I'm using gmake (v3.81) to build some c executables. As the first step in the process I run the files through a preprocessor (for embedded SQL). The preprocessor completes successfully, but the gmake reports an error and discontinues buiding the remaining dependencies...
make *** [myfile.c] Error 4
which (according to /usr/include/asm-generic/errno-base.h) means "interrupted System Call". My preprocessor doesn't raise any signals, so I'm not sure what's causing this error.
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Nov 6, 2010
I have been assigned to implement a system call that report the system statistics over all memory which are
Total Pages in Active LRU list
Total Pages in Inactive LRU List
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Apr 3, 2011
in below program why was new_args[0], rather than the reference the_cmd, passed to the execvp system call?
Code:
/*
A _very_ limited shell program
[code]....
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Nov 8, 2010
I need to allocate a % of the total system memory for a buffer but what is the best method to determine how much memory is in the system? So far the only way I have found is to get the pages of memory:
Code:
long sysconf(_SC_PHYS_PAGES)
Is that the only option?
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Dec 8, 2010
I have a process that forks, where the childs puts some data of random size and exits while the parent should get the data and does some manipulation.. here I have used a pipe for child to write the data and parent to read the data.. Child simply dumps the data, and the data is of any size even child and parent doesnt know.
I have used select in the parent to see whether there is any data coming on the reading end of the pipe.. if there is a data.. I copy into a buffer.. Im reading the data continusly when the child exits after closing the writing end of pipe. Parent gets blocked on the read part But my question is how parent know the other of pipe is closed when using the select call. In otherwords.. while using select in readfds, how would i know the other end has closed the pipe..
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Aug 30, 2010
I successfully added a new system call in CentOS Kernel but I don't know where to view it! My kernel version is -2.6.32.5
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Mar 24, 2011
how to create a new system call Linux? what is the process of creating ?my project is to create a system call for displaying owner of a file..where exactly we have to write the system call code? and where are the places need to change ?
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Sep 19, 2010
I'm new to C language and some help finding places in the following code where a system call is made and error checking is not done. I found one but since I don't know C language at all I'm not exactly sure what else to look for. Link to my file: [URL]...
I found one and added error checking:
if (setoutpipe){
//Changes: Added error checking to the system call close()
//Orginal Code: close(pidefd[1]);
if(close(pipefd[1] != 0){
fprintf(stderr, "Could not close piple.
");
exit(255);
}
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Jun 9, 2011
I have added a new system call for kernel version Linux 2.6.25-14.fc9.i686. after kernel compilation and running the user mode program i am getting the below error
Error :: Function not implemented
Error number 29
I cannot find the syscall_table.S or entry.S file in the source code , so i didn't made the entry of the syscall in this file, how much necessary the entry of syscall presence in this list and how to get this file?
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Apr 2, 2009
I want to test my system call that be goint to add to kernel, But when i finish compiling kernel, i found my system call code not work. the code i want to return the system time "struct timespec":
/*----------Start of mycall.c----------*/
#include <linux/linkage.h>
#include <linux/time.h>
#include <linux/kernel.h>
[code]....
so i want a method to test the new system call before compiling kernel.
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May 6, 2011
Anyone know the reason why a sleep( ) on a Redhat Linux OS would cause the system to indefinitely hang? It's doing this every 10 or so calls in my program and I have to press the reboot button on my computer. My program is reading from a UDP port that has messages sent to it 20 times per second. When I sleep I assume the internal UDP buffer is getting more and more filled.
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Apr 2, 2011
i've written small tool in C which makes measurements on my router (OpenWrt White Russian).
It is working as a deamon. If the tool is started manually, everything works fine. If it is started per script on startup, the following system call doesn't work :
Code: sprintf(command,"/bin/cat /root/%s%s | /usr/bin/ssh -p2222 user(at)host -i /root/.ssh/id_rsa "/bin/cat >> result/%s%s"", apmac, source, apmac, dest);
rc = system (command); the returned rc in this case is 256.
first i thought it is a problems with the user rights for the tool, so i have added +s to it. but that didn't help. as i said, when the daemon is started by hand, the system call works fine.
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Jul 30, 2011
I am making a library, but I am facing a strange problem while sending data over network using ethernet.
I am sending 39 bytes of the data from one server to slave application but some time slave receives 39 bytes and some time it receives 29 bytes. And when ever slave receives 29 bytes all the memories to which my pointers are pointing get changed. This problem is only when I am sending data from the server to slave, while sending data from slave to server I am facing no such issue.
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Sep 8, 2010
I have a script for dd command and i am using it in an application using system() call. Now i want to have the output of the script file (i.e output of dd command) in the application file itself.
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Nov 29, 2010
In practice I have a script that call a java program that call a linux system command. The script if I run it, from a shell functions well,so it is not a java problem. The problem come out when i put this script in a crontab schedulation. The result in this case is that java do not execute the system command. I think it depends on crontab
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Sep 29, 2010
we have a multi threaded program on Linux where one thread is waiting on poll() system call with event set to POLLIN, & another thread has closed the same socket fd (which is passed to poll) , but the poll() did not return, is this the expected behavior? From man page of poll we found that the poll should return POLLNVAL if the socket fd is closed, is my understanding correct or is there any bug in the poll()?In Solaris we observed that the poll system call is returning with POLLNVAL if the socket is closed.
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Nov 20, 2010
Does anyone have straightforward simple example document for adding a system call on fedora 14 kernel?
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Dec 10, 2010
I have the following code:
Code:
#include <stdio.h>
#include <stdlib.h>
int main() {
system("ps -ef | grep myprocessname");
return 0; }
When I run this program it outputs the following list of running processes:
Code:
root 10279 10275 0 13:02 ? 00:00:00 myprocessname myvar1=value1 myvar2=value2
root 10341 10337 1 13:02 ? 00:00:00 myprocessname myvar1=value1 myvar2=value2
What I want to really do is instead of writing the output to screen I want to read the output and parse the various values value1, value2 etc. What is the best way to do this?
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Nov 5, 2010
Am getting errors about "mysql_connect()" for the following code:
Have compiled PHP with MySQL support using the following:
Thought PHP 5.3 has a built-in replacement called mysqlnd, and there's no need to install "php-mysql" RPM.
However, according to the following site this is still required: [url]
Give me an idea whether I really have to install php-mysql RPM in order to use mysql_connect() for PHP?
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Jan 20, 2010
I've been requested to modify a perl backup script we use which mounts a networked NAS machine. The actual mount command is called inside a system() command. In testing, I can do a test of the return value, so I'm able to tell whether or not I've mounted properly, but I can't make heads or tails out of the return on deliberate errors. (Such as mounting a non-existent box.) I'm displaying the returned value, which is 256 in my tests. The man page for mount listed error messages with values from 1 to 64, but no higher. Am I drawing this error value from the system command somehow? And what would be the best way to determine what this error means?
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Jan 25, 2010
Code:
I am trying to do a search to check if the input is using alphabets and nothing else.
I tried using [[:digit:]] and [[:alpha:]] but none seems to work
When i use digit, it read 22.k as alphabet and not as a wrong syntax.
For alpha , it does not allow me to input data which has spaces such as " hello world".
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Dec 17, 2010
@work we use Zabbix and also IP-audit for monitoring. Each day we have a list of outgoing SMTP-servers on our IPaudit server.
This script will take that list and check them all against a whole bunch of DNSBL's
# cat /usr/local/sbin/check_rbl
Code:
#!/bin/bash
#####################################################
# check_rbl
#####################################################
# 17-12-2010 by JP van Melis
#
[Code].....
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Feb 23, 2009
I was wondering if there was a way to add a switch to a gcc/g++ call everytime. I have a few libraries that I need to compile for different processors. Each has a makefile which calls gcc to compile. Here is the best option I could come up with so far:Include a Makefile and define CC as gcc -mcpu=xxx.
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Dec 3, 2010
iam trying to add a system call to the kernel version 2.6.33.7.Iam running fedora 13.I have followed all the steps given in this <hekimian-williams.com/?p=20 -> tutorial,but iam getting a error in make saying undfined reference to mysyscall in syscall_table_32.
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Sep 28, 2010
what is what is signal 0 in linux system call ?i can't find that in kill -l signal list . i need to know what is signal 0 . * for examples signal 1 is SIGHUP and signal 2 is SIGINIT . what is signal 0 ?
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Jan 18, 2010
what i am trying to do is to allow the user to key in data such as "23.23" or "24" , as it is the price of certain objectsHow am i able to design a check which will allow me to prevent users from typing in input such as "ab.21" or "rfrr" as this field is purely a numerical field. The problem i am facing is i tried using this search code.
Code:
echo "read this"
read this
[code]....
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Jan 8, 2010
i have only basic knowledge of C so guys plz help me...is C language support call the C executable inside the C ?example contect mainA.c have a many function define in the struct,when i compile mainA and make a executable the name is ( A ),can i use executable C inside the C <my C program call the executable ( A ) > .
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Jun 1, 2010
I have created a executable file using c and I have also created a GUI using GTK+. Now how can I call the executable file from the GUI with arguments passing to the executable file.
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Sep 29, 2010
There are examples everywhere about calling f77 subroutine from IDL, but I have not found any material about IDL calling fortran written in f90 way(free style). I tried the following example, but write the subroutines in free style. When I run the makefile, it gives an error 'undefined reference to main_'.
Code:
SUBROUTINE SUM_ARRAY(argc, argv) !Called by IDL
INTEGER*4 argc, argv(*) !Argc and Argv are integers
j = LOC(argc) !Obtains the number of arguments (argc)
[code]....
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