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.

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14 views

How Can I recieve messages from more than one named pipes?

I have to use fifo in my code. I use sock to accept new client. For each client I create new thread to send and recieve message to him. In the function of the thread I use fifo to send and recieve ...
0
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0answers
42 views

How to make a fifo in C? [migrated]

I have to use mkfifo in my C program in Ubuntu. But I have an error when I compile: no such file or directory . I think the problem because I have not set the panel_fifo environment variables. But I ...
1
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1answer
817 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 ...
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0answers
30 views

Why use mmap over fread? [migrated]

Why use mmap as opposed to reading from a filestream in chunks into a byte array? I guess I just never thought about using mmap before. mmap(2) fread(3) // Open the file // Read from the file ...
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votes
1answer
31 views

Meaning of '&' in C (here in linux kernel function-like Macros) [closed]

#define TCP_SKB_CB( __skb ) ((struct tcp_skb_cb *)&((__skb)->cb[0])) What does the & mean in this context?
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0answers
20 views

Link Speed for wireless connections [migrated]

I am working to implement a benchmarker for wireless connections. How can I determine the link speed in mbps? I am working with C language and Linux system.
1
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0answers
9 views

Xlib: resize window containing a pixmap [migrated]

Related to how-to-resize-a-pixmap-with-xlib. As it was concluded in the abovementioned topic, it's impossible to resize a pixmap. What about window, after pixmap is copied into it? In the example ...
2
votes
1answer
1k 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 ...
0
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0answers
17 views

fsync on newly created folder? [migrated]

Can anyone explain why fsync can return EINVAL when I pass folder descriptor in it? There is my code, it is pretty simple: #include <dirent.h> /* Defines DT_* constants */ #include ...
0
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0answers
15 views

Any GNU C examples where faccessat() function (or equivalent) is used? [migrated]

In reading IEEE Std 1003.1 (POSIX Base Spec) regarding access(), I came across this note: "The purpose of the faccessat( ) function is to enable the checking of the accessibility of files in ...
3
votes
2answers
51 views

When does cat finish reading from a pipe?

Given the following code, why does cat only print the contents of the pipe after I've typed \n or CTRL+D? What are the conditions for cat to actually print what it read? #include <stdio.h> ...
0
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0answers
10 views

How do I write commands to a ttyACM0 device and obtain the resultant information data using C/C++ [migrated]

I am currently stuck with a task of retrieving data from a decoder that monitors 6 joint positions of a robot arm. This device has a USB interface that runs as a serial CDC device. An ASCII command ...
3
votes
1answer
42 views

Memory layout of dynamic loaded/linked library

when loading a shared library in Linux system, what is the memory layout of the shared library? For instance, the original memory layout is the following: +-----------+ |heap(ori) | +-----------+ ...
2
votes
1answer
42 views

How can I (easily) map a block device node to the directory it's mounted on?

I need to find (in C or C++) the used space on a filesystem (Linux) when being provided only with the disk block device name and the partition number. For most filesystems I can go: Craft a dev ...
3
votes
1answer
33 views

Io redirection vs file logging performance c/c++

Is there a performance difference from a latency point of view if we do a regular printf and redirect stdout to a file when running the program ( e.g., ./a.out > log.txt 2>&1 ) vs using fprintf ...
4
votes
1answer
7k views

Default stack size for pthreads

As I understand, the default stack size for a pthread on Linux is 16K. I am getting strange results on my 64-bit Ubuntu install. $ ulimit -s 8192 Also pthread_attr_init(&attr); ...
1
vote
1answer
67 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
1answer
28 views

Can I use LXC library in my c program?

Currently, I am designing a c program that will create multiple container and put different applications into them separately to achieve isolation. Is it possible to leverage LXC library to it? I ...
4
votes
1answer
446 views

Can I write C programs for Linux on OS X?

In case I'm writing a program (of any kind) in C, that is meant to be run on Linux environment, can I write it under OS X? (concurrency wise for example) I'm asking this because I like programming in ...
3
votes
2answers
195 views

The «sh» being launched with execl() becomes a zombie

I am spent whole half a day, but still couldn't figure, why is the dash being launched with execl call just becomes a zombie. Below is a minimal test case — I'm just fork a child, make a duplicate of ...
0
votes
1answer
17 views

What happens to TCP when a write fails to enqueue with the device tx ring?

Lets say the device tx ring is full and you do a normal C non blocking write(fd, buff) to enqueue data in the TCP SND buffer. What happens when this fails? In UDP - the packet would be dropped but ...
1
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1answer
21 views

Distributing app with .so files?

I'm trying to make a game in C with SDL and OpenGL. Q: Will my game run on computers without SDL installed if I ship the .so files in my game folder? I mean adding the .so files somewhere in the game ...
8
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2answers
40k views

gcc can't link to pthread?

I have recently installed XUbuntu 11.10 64bit, but I am having problem compiling the most simple pthread example. Here is the code pthread_simple.c: #include <stdio.h> #include ...
4
votes
1answer
356 views

why is “timer_t” defined in “time.h” on Linux but not OS X

While I was reading a C source code files, I found this declarations. (This source code was written for linux system program. This is very important information) #include <time.h> #include ...
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4answers
6k views

/usr/ucb/cc: language optional software package not installed

I tried to compile some C code to get object file from a shell prompt: $cc a.c But this gives me the following error: /usr/ucb/cc: language optional software package not installed How can I ...
19
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6answers
9k 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 ...
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0answers
66 views

Reading the program header contents of an ELF file

How is it possible to extract loadable program headers individually from ELF files? By examining a binary using readelf one can get output similar to: $ readelf -l helloworld Elf file type is EXEC ...
0
votes
1answer
46 views

introduce a c script in a bash file [closed]

My problem is to recover data keyed in text file in bash. I seek the command that can perform this task and I used sed, awk and even cut but I have not succeeded. One friend of mine suggested to ...
0
votes
1answer
38 views

How do I execute a parted command with a C function?

I would like to execute the Linux command "parted" through a C language function? I am using Linux Ubuntu , eclipse. Thanks!
0
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0answers
20 views

How to obtain block device label [duplicate]

I have a tricky problem. I have a block device connected to SLES11, it is present in /proc/partitions but it is not mounted (not present in /proc/mounts). From C code I want to find the block device ...
1
vote
1answer
241 views

Reading the contents of an ELF file (programmatically) [closed]

I am trying to retrieve the contents of an additional section within an ELF binary. At this point, I'm using the following code to retrieve the name of each section: #include <stdio.h> #include ...
0
votes
1answer
31 views

Pulling log messages for a particular log in systemd journal?

I was wondering if it is possible to pull log messages for a particular log with systemd's journal logging. For example, when I open a log in C, openlog('slog', LOG_CONS | LOG_PID, LOG_LOCAL1), to ...
1
vote
1answer
50 views

How to run smartctl as root without switching to root?

I have this C code that runs smartctl command and takes its output: #include <iostream> #include <cstdio> #include <cstdlib> using namespace std; int main() { cout << ...
0
votes
1answer
75 views

Trying to make a Universal Makefile

I'm working on my own netfilter module for the first time. According to internet documentation, The simplest module contains the following C code: //'Hello World' kernel module, logs call to ...
1
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3answers
93 views

loop test strings to see if input is valid for C program input

For example I have a file filled with some pretty gnarly strings. 12345678900 1111111111111111111111111 ...
0
votes
1answer
202 views

C/C++: Running multiple commands as root

I want to execute commands within my C program. However, I need root priviliges to create some folders. I run the following: system("echo <rootpass> | sudo cd <folder> && make ...
-2
votes
1answer
87 views

how to return file descriptor in c [closed]

I am confusing with this. fp=fopen(filename,mode); what is the value fopen() return to fp. is that value is file descriptor integer? is fp called as stream ? if not how to return a ...
0
votes
1answer
65 views

How to select read/write time and again? [closed]

This program only waits one time and I don't understand why. Actually, I don't think this question should be put on hold as off-topic. #include <stdio.h> #include <sys/types.h> #include ...
2
votes
2answers
64 views

linux setuid does not work

I am learning linux suid,so I have written a small c program with the following content to test it #include<stdio.h> int main(){ system("echo 100 >> test.txt"); return 0; } -rwsr-xr-x 1 ...
0
votes
1answer
1k views

“fatal error: stdio.h : No such file or directory” while compiling a C file [closed]

Trying to compile following code in terminal i got root@debian:/home/mz2/Documentos# LANG=C ./soma.c ./soma.c: line 2: syntax error near unexpected token `(' ./soma.c: line 2: `int soma (int a, int ...
0
votes
0answers
49 views

keyboard still working after calling free_irq(1, NULL);

I'm developing a kernel module which free the IRQ number 1 in order to disable the keyboard in Intel architectures. according to wikipedia the IRQ 1 is used for keyboard. but after building and ...
18
votes
4answers
2k views

How to dump a binary file as a C/C++ string literal?

I have a binary file I would like to include in my C source code (temporarily, for testing purposes) so I would like to obtain the file contents as a C string, something like this: \x01\x02\x03\x04 ...
0
votes
0answers
29 views

how to define the top dir in automake system?

I usually use a typical steps to generate the makefile, and firstly I use the "build.sh init" to generate the configure file, and then I use "configure" to generate the makefile with makefile.am file. ...
0
votes
1answer
145 views

Compile OS with gcc and ld on Linux

I'm practicing operating system development and am having trouble getting gcc and ld to produce pure binary without any metadata or section labels. For example: int function(){ return 100;} would ...
0
votes
1answer
793 views

Cabal error: Cannot run c compiled programs

I have an old version of cabal-install so I downloaded cabal-install 1.20 and When installing it errors out. Additional note: ghc 7.8.3 OS: CentOS 6.6 Error: Building network-2.4.2.3... ....... ...
1
vote
1answer
256 views

Cannot find -lgcc

I'm trying to compile my next basic c program after hello-world. This contains two supporting modules. I have Ubuntu running in a VM through VirtualBox on a mac. Everything is up to date but I ...
5
votes
4answers
8k views

How do I kill all a user's processes using their UID

I want to kill all running processes of a particular user from either a shell script or native code on a linux system. Do I have to read the /proc directory and look for these? Any ideas? Is there a ...
1
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0answers
2k views

Getting “cannot open shared object file: No such file or directory” error while run time

I have successfully compiled the file but now I am getting following errors export LD_LIBRARY_PATH=/opt/mcr/v717/sys/java/jre/glnxa64/jre/lib/amd64/server/:D_LIBRARY_PATH ./invoke ./invoke: error ...
2
votes
2answers
247 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, ...
0
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1answer
25 views

-fPIC Flag System-wide?

Position Independent Code means that the generated machine code is not dependent on being located at a specific address in order to work. and the jumps are relative. So is it OK to declare -fPIC ...