C is a general-purpose computer programming language used for operating systems, games and other high performance work and is clearly distinct from C++. It was developed in 1972 by Dennis Ritchie for use with the Unix operating system.
0
votes
0answers
5 views
How to know if the following function is returning the correct result or an error condition in `jansson`?
I am using the jansson JSON library for an application. I was reading the API and came across these functions: json_integer_value, json_real_value and json_number_value.
The first one returns the ...
0
votes
0answers
17 views
#define SYSCALL_DEFINEx(x, sname, …) [migrated]
In the 3.14 linux kernel there is the following macro :
#define SYSCALL_DEFINEx(x, sname, ...)
It's located in include/linux/syscalls.h.
I added a syscall in the source, I compiled it and I made ...
0
votes
0answers
17 views
Cgi C program stopped working with error 500 [on hold]
My hosting owner did something with his Linux software on the server.
And my C cgi program returns error 500 now.
It worked good before.
I tried to recompiler on Debian 7. The same error.
Maybe it is ...
0
votes
1answer
13 views
Linux [admin] How to test pivot_root?
I want to test the pivot_root command line, which moves the root file system of the current process to the directory put_old and makes new_root the new root file system. ...
1
vote
0answers
16 views
PAM authentication program in C recognizes only the logged in user [closed]
I am trying to write a C program to authenticate users using PAM. Here is what I have at present:
#include <security/pam_appl.h>
#include <security/pam_misc.h>
#include <stdio.h>
...
1
vote
1answer
10 views
snd_rawmidi_open() waits forever - no error message
I am trying to use ALSA for MIDI purposes in C.
My problem is, snd_rawmidi_open() sort of "crashes" (waits forever like a while loop) when using valuable arguments :
#include <stdio.h>
...
2
votes
0answers
17 views
Make GNU indent break long comments
Is there a way to convince GNU indent to break long comment and change it to multiline comment?
Something like this:
// Very long comment, longer than 80 characters. Just imagine that.
To this:
/*
...
2
votes
2answers
72 views
Linux cannot compile without GCC optimizations; implications? [closed]
One can find several threads on the Internet such as this:
http://www.gossamer-threads.com/lists/linux/kernel/972619
where people complain they cannot build Linux with -O0, and are told that this is ...
0
votes
0answers
14 views
Hardware address of network interface using ioctl on AIX [migrated]
I want to get hardware address of network interface on AIX using ioctl.
Like in Linux we get it through:
ioctl(sockFd, SIOCGIFADDR, ifr_p);
I didn't find SIOCGIFADDR flag in ...
4
votes
1answer
78 views
How to compile programs on Linux systems when I don't have sudo privileges to install the dev dependencies [duplicate]
How should I go about compiling programs that depend on libraries whose development packages (headers and such) aren't pre-installed on the system when I don't have sudo access?
In this particular ...
0
votes
0answers
24 views
Inotify notifies only single change
I set the inotify_add_watch to watch /dev/disks.
The entries in this directory are: by-id and by-uuid.
When I plug-in a pen-drive, this directory gets added with two more directories: by-path and ...
3
votes
1answer
88 views
How to create GUIs (such as menuconfig) with lxdialog
I try to generate a menuconfig by my own with the help of lxdialog (source: lxdialog). Unfortunately this is not so well documented as I wished for. Example:
So what I did: I included these files ...
1
vote
0answers
25 views
CPUFreq Kernel module
I would like to try the CPUFreq module on my board (Marvell Soc based on ARMv7 running a v3.15 linux kernel). My architecture is obviously not supported by the default source code (located in the ...
5
votes
4answers
553 views
chdir(<directory>) doesn't change directory after exiting to shell
I wanted to make a simple C program to change to my project directory. Its content is following:
#include <unistd.h>
int main(){
chdir("/home/enedil/projects/algo");
return 0;
}
I ...
0
votes
1answer
54 views
What are the disadvantages of uClibc?
I try to speed up my boot sequence, and somebody recommends to use the uClibc instead of Glibc. I've built an image with it, it gets smaller and faster to boot — but at which cost?
Does anyone know ...
3
votes
1answer
103 views
How to programmatically retrieve the GID of a running process
I need to write some C code to check the effective GID of a running process whose PID I know. I've not found any direct way to do this. There are a number of heavyweight kludges I could use, such as ...
2
votes
0answers
181 views
what device name should I have to give in snd_pcm_open other than “default”
I want to record sound from 2 devices simultaneously:
internal mic
external usb webcam mic
Using pulseaudio sound controller, I set either of these devices as default and could record sound with ...
1
vote
0answers
66 views
Limit program execution to a list of arguments
I would like that my Unix users can only run a specific command insecurecommand with a controlled list of arguments stored in a file.
The only solution I have found at this time is to :
Create a ...
0
votes
0answers
372 views
GTK3+ and C++ on OSX - “No GSettings schemas are installed” error
I'm trying to run a C++ example with GTK3+ and GStreamer components on OSX. I can gcc compile the source with:
gcc -o basic5 basic-tutorial-5.c 'pkg-config --libs --cflags gstreamer-1.0 ...
2
votes
2answers
135 views
How does a parallelized Python program look with top command?
I work on a shared cluster. I've seen people run parallelized c code on this cluster which, when I use top to see what processes are running, are shown to be using (for example) 400% of the CPU, ...
2
votes
2answers
65 views
What is bitwise.c~? [duplicate]
I am new to Linux Debian and I am trying to made a program to experiment bitwise operators. The name of the program is bitwise.c
Before compiling the program, I decided to look at the directory just ...
2
votes
1answer
167 views
closing the unwanted file descriptors
I am trying to understand how pipes work . This code snippet is from some website .
So my understanding of the program goes like this :
When we do pipe(fd) then fd[0]=3 and fd[0]=4 ( assuming only ...
3
votes
1answer
58 views
Is each process considered a thread?
Is a Linux process considered a thread?
For example, if I write a simple c program that calls pthread_create to create a new thread in main(), does that mean that I now have 2 threads, one for ...
3
votes
0answers
149 views
How do I use ctags functionality in vim with cscope installed?
When I install cscope by adding the line Bundle 'chazy/cscope_maps to my .vimrc file, my tags menu (g+[) is replaced with a cscope list, which seems to contain a list of files where the tag is called, ...
1
vote
1answer
1k views
Default stack size for pthreads
As I understand the default stack size for a pthread on linux is 16K. I am getting strange sesults on my 64bit ubuntu install.
$ ulimit -s
8192
Also
pthread_attr_init(&attr);
...
0
votes
1answer
62 views
Difference between maximum resident set size as reported by /usr/bin/time vs. getrusage?
I ran the command a.out like this:
$ /usr/bin/time -f"%M" ./a.out
a.out also uses the function getrusage() and prints:
printf("%ld",ru.ru_maxrss);
where the first ru is the struct. When I run ...
1
vote
0answers
80 views
how to get user's last login including the year in C [closed]
I'm trying to write a program that can get the user's last login time. Then i want to do something with the data. eg. check which user havent login for 90 days. So I tried using last command. This ...
9
votes
5answers
1k views
What is meant by “a system call” if not the implementation in the programing language?
I would like to understand the term "system call". I am familiar that system calls are used to get kernel services from a userspace application.
The part i need clarification with is the difference ...
1
vote
1answer
300 views
ioctl: invalid argument for HDIO_GET_IDENTITY
I wrote a program to get the details of hard disk drive using HDIO_ ioctl calls.
For writing program, I'm referring Documentation/ioctl/hdio.txt in kernel source(2.6.32).
Here is my main part of ...
1
vote
0answers
38 views
How to get the authentication status from the last PAM module run
If I have the following PAM stack:
auth required default_pam.so
auth requisite my_custom_pam.so
....
How do you obtain the authentication status from the last/previous PAM module run for use in ...
0
votes
0answers
146 views
How do I run TinyWM inside Xephyr?
I'm trying to get into Window Manager hacking, so I found TinyWM and tried running it inside a Xephyr window.
I tried:
Xephyr -screen 1024x768 :1 &
DISPLAY=:1 ./tinywm &
DISPLAY=:1 scite ...
0
votes
1answer
74 views
Error: Missing newline before EOF - inserted
In my application I am inserting some files in main file. In that there is common header file to all the code files (*.c). This giving me error:
D:\New folder\COM_Port_Cont\COM_Port_Task.h(268) : ...
10
votes
6answers
1k views
What C library version does my system use?
How can I tell for sure what userland C library my system uses? Possible reasons to need this information include:
There's a gigantic source package I am considering downloading which I'm sure will ...
0
votes
1answer
86 views
libext2fs gcc linking error
I am writing a C program which uses libext2fs:
#include <ext2fs/ext2fs.h>
int main(int argc, char *argv[])
{
char *fsname = argv[1];
errcode_t err;
ext2_filsys fs;
err= ...
5
votes
3answers
372 views
Are there “esoteric” (weird) but standards-compliant C compilers or runtimes?
As we know, the C standard does not specify a lot of details of the implementation, for example value of NULL pointer, order of bits and bytes (endiannes), alignment in structs and of stack ...
1
vote
0answers
119 views
How to cause memory fragmentation on a Linux based embedded device?
Hardware
ARM
What am I trying to do:
Answer: I am trying to create memory fragmentation on a Linux 2.6.31 based swapless embedded device.
Why:
Answer:I am trying to port some patches to Linux ...
1
vote
2answers
472 views
Writing own daemon. systemd error: Failed to read PID from file: Invalid argument
I'm trying to write own daemon a la very simple MPD (it's operating systems laboratory work). I made it work: it starts like a daemon (output of ps):
1 14877 14877 14877 ? -1 Ss 0 ...
2
votes
1answer
63 views
Can you use LXC through C?
I want to use LXC to 'container' plugins my application is loading. Am I able to do this through C? I have been Googling a lot about it, but there don't seem to be any headers, only scripts that can ...
3
votes
1answer
304 views
How to let a user execute a script owned by root? Setuid doesn't seem to work anymore [duplicate]
I have some bash scripts that I use with the user 'root' to manage iptable rules.
The problem is that I want these things at the same time:
The script must be owned by root
Permissions must be 700
...
-2
votes
1answer
78 views
How to compile c, c++ and python code as “Released/Final” version? [closed]
I want to know if there are ways to compile C, C++ and Python code in order to not be able to reverse engineering it over Linux or not?
I have heard there are some ways over Windows to do it, but I ...
8
votes
7answers
1k views
Possible to find out the sizes of data types (int, float, double, …) on a system, without writing a C program?
Is it possible to find out the sizes of data types (int, float, double, ...) on a Linux system, without writing a C program?
Would the results for C same as for C++, and other programming languages ...
0
votes
0answers
137 views
Reading from named pipe freezes when piping tshark output
I'm trying to implement a web prefetching system. The purpose of a system like this is to “predict” future requests and prefetch them.
The system builds a predictive model from web navigation logs ...
2
votes
0answers
128 views
How can I compile minix when I make changes in libraries
I am looking for a way to compile minix. The make hdboot command seems to do nothing with the directories under /usr/src/lib. I changed only one .c file in syslib. Do I have to do make world for this ...
0
votes
3answers
107 views
In makefile when do we use .o files?
In the following make file, what is the significance of adding .o files instead of .c files?
CC=gcc
CFLAGS=-I.
hellomake: hellomake.o hellofunc.o
$(CC) -o hellomake hellomake.o hellofunc.o ...
5
votes
2answers
341 views
What would I get when sudo a kernel-destructive program?
It suddenly comes to me how easy it will be for a sudoer to crash the kernel, so I tried something like this:
#include<stdio.h>
int main(){
printf("hello world");
int a;
...
2
votes
1answer
733 views
Error compiling FTDI VCP drivers: Cannot find version.h
driver installation fails of FTDI VCP driver during make install.
Running ElementaryOS with kernel 3.11.0-14-generic
make install
awk: cannot open ...
2
votes
0answers
145 views
Writing to Arbitrary Memory Addresses [closed]
I'm reading "Art of Exploitation 2nd Ed." and I have a question regarding a section on format string attacks.
Target program
Below code (fmt_vuln.c) is a target program.
#include <stdio.h>
...
0
votes
0answers
38 views
How to `cat` file with syntax highlight? [duplicate]
In my hello.c:
/* Hello World program */
#include
main() {
printf("Hello World");
}
How can i cat this file on terminal with syntax highlight?
1
vote
3answers
116 views
Is there any manual about C in Linux? If any, what is it?
While I find that we can read some manuals about Library calls (C library functions) & acsii in Linux. But I still do not find any manual about C precedence order so far.
So you can recommend ...
2
votes
2answers
231 views
How to make processes not die after its parent dies?
I've been messing with forkbombs and noticed that if I just fork() processes repeatedly, killing the initial process will bring down the whole tree. This is not the case for forkbombs written in BASH ...
