I have started learning C and am following Ivor Horton's "Beginning C - From Novice to Professional". I've noticed that in the book the structure of the main function is:
int main (void) however on the internet I found a lot of cases: void main (void)Which one is preferred and why?
Kindly take a look at the code below :
Code:
#include <stdio.h>
struct test
{
int i;
int j;
[Code]....
why i am getting this error. I know the error is occuring because i have assigned values to obj.i and obj.j outside main(). But i want to know why do that result in an error. From my part i have created an object 'obj' of stucture 'test' and assigned values to its variables.
I am writing a function(in C language in Linux) to initialize an array of a structure from a mysql table by calling a function by reference but I have a problem with call this function by reference . this is my program:PHP Code:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
[code]...
I have a project in which many processes run. p1,p2,p3.
->There are some .so files are included in some process when needed example ppp.so in process p1 (when ppp is needed and will go like a plugin) but it has a init () function how a process includes a init() function ?
->process p1 has main function i.e main()
->so evry process has main() right ?
what is the difference between init () and main () functoins. where is init () used and how many init() a process van have ?
it possible to access main program function from dynamicallyinked library in c language?For example:main.c:
Code:
#include<stdio.h>
void func()
[code]...
This is not a Linux specific question.Can someone over here give me an example where I have to run the main function infinitely?
View 4 Replies View RelatedI've having problems with my Makefile.
I'm trying to create a program from 2 files - main.cpp that contains the main function, and modules.c that contains the definitions of the functions that are called in main(). modules.c only contain function definitions, no main function.
My Makefile is as follows:
Code:
I have included "modules.h", which contains all the function declarations, in my main.cpp.
When I try to make using this Makefile, I get the error
Code:
If I switch the order of modules.o and main.o in my $(TARGET) line, then I get errors that say "undefined reference to" the functions I have defined in modules.c, in main.cpp.
user@ubuntu:~/Documents/C$ man host_ent No manual entry for host_ent How to install the manpage for host_ent or in_addr under ubuntu?
View 1 Replies View RelatedCode:
#include <iostream>
using namespace std;
[code]...
I am doing some Linux kernel programming for my research project. I need to record the timestamp (by using cpuid and rdtsc) when an interrupt handler (top half) is first invoked. Due to the time critical nature of the problem itself, I have to do the timestamping inside the interrupt handler itself (the first operation when the handler is called). However, I understand that tasks that are not so time critical should be deferred to a tasklet function (bottom half) for processing because other interrupts are disabled in a (top-half) interrupt handler. I am currently out of idea on how I can pass the timestamp information that I have obtained in the interrupt handler to the corresponding tasklet function.
View 2 Replies View RelatedI want to declare a function in a function, but had no success till now, see the error code below and visit the project at sourceforge
[Code]...
I looked on the net for such function or example and didin't find anything, thus after having made one i guess it would be legitimate to drop it to see what others thinks of it.
#!/bin/bash
addelementtoarray()
{
local arrayname=$1
[code]....
How do you malloc a struct in C? I have a structure of the form:
Code:
typedef struct child_req_to_parent
{
[code]...
I have a struct (small instance so not using code brackets )
struct random {
int a;
int b;
}example;
What i am trying is
example={0,0};
and it gives an error how to initialize all the entries within a struct to zero? In the above example i have used integers but what if they are some other data structure for example another structure?
I am learning Kernel Programming these days I came across a structure
Code:
static DEFINE_PCI_DEVICE_TABLE(rtl8139_pci_tbl) = {
{0x10ec, 0x8139, PCI_ANY_ID, PCI_ANY_ID, 0, 0, RTL8139 },
{0x10ec, 0x8138, PCI_ANY_ID, PCI_ANY_ID, 0, 0, RTL8139 },
{0x1113, 0x1211, PCI_ANY_ID, PCI_ANY_ID, 0, 0, RTL8139 },
{0x1500, 0x1360, PCI_ANY_ID, PCI_ANY_ID, 0, 0, RTL8139 },
[Code]...
I am implementing c program to access ext3 file system's metadata. I want to know how to access members of the in-memory superblock structure. I am able access on-disk ext3_super_block structure but dont know how to access in- memory structure and its members.
View 1 Replies View RelatedI have a mxn matric (which is my simplified way of saying it is RAM with bytes on it) Some of the locations on this metric is filled with some data and some places are empty. The mxn are very big numbers in size. I am trying to make a program so that if a system call wants to write some thing on empty locations on this mxn metric it should be able to do so without any problem. The thing which I want to understand or logic of a data structure is what data structure do you people feel should I be maintaining so that I can allocate the requested space immediately from the above mxn matric when some system call requests for some (k) number of locations from above metrics.
The logic initially I thought was to maintain a hashtable
1bytes requested----------> location 1,location 2,location 3.........location n
2bytes requested----------> location 1,location 2,location 3.........location n
3bytes requested----------> location 1,location 2,location 3.........location n
[code]....
but the problem with above logic is size of the pointers where I will be writing this problem is unsigned 64 byte.So to know location of one free byte if I am maintaining one pointer of type u64 this is not a feasible solution.
I wanted to implement a graph.By graph I mean to say that I am writing programs for BFS,DFS and other such stuff and want to see them in action. For this I started writing a program.The first entry point is to define a graph. I took a pen and paper and made a graph. Now to be able to code this in C.I defined a structure but I am finding problem in defining this structure. I looked into Google and came across incidence list and adjacency list representation [URL] after understanding that I am not able to understand how do I define my structure that would be a node in graph. Here is what my graph looks like
Quote:
|-----------31
| |
| 2---4---6---8
| |
[code]....
I am currently writing a program using raw sockets. This program is used to send out ARP reply frames. The problem that I have is that I do not seem to be able to fill out a structure that is pointing to part of a character array.
Code:
struct eth_header *eth;
struct arp_header *arp;
char buf[8];
eth = (struct eth_header *)buf;
arp = (struct arp_header *)(buf+sizeof(struct arp_header));
Whilst I can fill out the variables of eth, I cannot fill out the variables of arp. If I fill them out and then send the contents of the array using send to, only the first structure (the ethernet header) is sent out. The rest of the data appears to be the original junk data in the array. I have checked the address of the structure pointer and it is pointing to the right place in the array. If I write a raw sockets program that uses an IP header struct and TCP header struct I can point these into the array and write to both of them without any issues.
The difference here is that the call to socket is different:
Code:
/* For ethernet */
fd = socket(AF_INET, SOCK_PACKET, htons(ETH_P_ARP));
/* For IP */
fd = socket(AF_INET, SOCK_RAW, IPPROTO_RAW);
If I just create one structure containing all of the variables needed this gets around the issue, however, I would like to know what I am doing wrong in the first instance.
I have added new member "i_mymember" to inode on-disk structure in ext3_fs.h file and tried to access this in userspace program, but gives me error that "error: �struct ext3_inode� has no member named �i_mymember� "
I have compiled my kernel source code.
why this error is coming ...?
Options:A double linked list with fixed size character arrays. New nodes will be added when previous ones get filled. Dynamic arrays using realloc(). Linked list has the disadvantage of not having an O(1) search like an array but I think using realloc() will be more dangerous since it moves the whole block to a new location and if the new location is not big enough to hold the whole block, realloc fails !! this case will not occur with the linked list since its nodes are scattered.
View 14 Replies View RelatedI am writting a program that reads a text file (music.txt) & stores it in a Data Structure. I am a novice learning over the internet so I this is something I have never done. How do I do this?
Quote:
Write a program that reads the data from the music.txt file and store it in a data structure. To implement this data structure you must use an array of songs and each song must be represented by a struct with appropriate fields. So far all I can do is open to file to read it (very simple I know) but so far is it correct?
Code:
#include <iostream>
#include <fstream>
#include <strstream>
[code]....
I'm using ubuntu9.10 (x86_64) and have some code,
Code:
void show_utmp(struct utmp* ent)
{
time_t tmp;
if (ent->ut_type != USER_PROCESS)
return;
[Code]....
How can I disable structure alignment feature of gcc using command-line options ?I recently migrated to 64-bit OS, and doubt that I might be experiencing a structure alignment problem due to the new 64-bit architecture.I checked the sizes of the same C-style struct in both x86 and x86_64, and found out that they appear to be different by 20 bytes.I am not sure if this is due to structure alignment or the differences in data type lengths between two platforms.Hence, I will first disable the structure alignment feature, and then check the struct sizes again.
View 3 Replies View Relatedtelling the exact macro name and location, by which I can gain control over the following kernel base level structure
1. strct super_block of Virtual File System, for super block object.
2. strct inode for inode ofject of VFS.
3 file structure for file object of VFS.
in addition to these if you know location to access other kernel structure.Please let me know.My main objective is to get the access to the structure pointer of these structure by which i can have access over the individual fields o these structure.
I'm having problems with compiling recursive Makefiles in my directory structure:
My folder layout is:
top/|- one/|- one.c (With main function)|- zero.c|- two/|- two.cin my top folder the make file looks like:
Code:
MAKE_DIRECTORIES = one two
.PHONY: all
all: $(MAKE_DIRECTORIES)
.PHONY: $(MAKE_DIRECTORIES)
$(MAKE_DIRECTORIES):
@echo $@
$(MAKE) --directory=$@
in my one and two folder I have the following Makefile:
Code:
.PHONE: all
all:
@echo $@
$(CC) $(CFLAGS) *.c
But when I compile it from top folder: make
I get following output:
Code:
one
two
Which states that directory statement by echo in main Makefile is ok but the files are not compiled in one and two.
I am trying to create a simple bash script to rsync some folders within a directory stucture. I am using wild cards, in the rsync source directory structure, but my command always fails. I believe it is the way I am using wild cards within my for loop. Here is my command ;
Code:
for seq in `cat test.txt` ; do rsync -nvP /folder/folder/folder/folder/folder/**/$seq /folder/folder/folder/ ; done This always fails, where if I do a ls to the destination, to test the path, it always works.
Has any one ever come across a book on Linux programming which explains a Library structure in depth?
View 3 Replies View Related[Code]....
if the address of stWndClass is 403000h, WHY it would be compile as mov eax,[esi+403004] and the first one would be mov eax,[esi+4]? I know how to get the values 403004h and 4,but do not know why.
I want to read an ftp site [URL]...and download the sub-directory structure and ONLY the tagfiles to the local directory.
FROM THIS:
Code:
slackware
+--a
| |aaa_base-12.2.0-noarch-1.tgz
| |aaa_base-12.2.0-noarch-1.tgz.asc
[code]....
I tried wget + grep but that didn't work too well.