Sponsored Content
Full Discussion: Extern variable.
Top Forums Programming Extern variable. Post 302217936 by Tanvirk on Thursday 24th of July 2008 12:50:52 AM
Old 07-24-2008
Extern variable.

file1.c

Code:
int a1;
int main()
{
        a1 = 2;
        printf("\na1 = %d\n", a1);
        next();
        printf("\na1 = %d\n", a1);
        next1();
        printf("\na1 = %d\n", a1);
}

file2.c
Code:
#include <stdio.h>

int b1 = 0;
void next(void)
{
        char a1;

        a1 = 'a';
        b1 = 77;
}


file3.c

Code:
int a1;
void next1(void)
{
        float b1;

        b1 = 20.3;
        a1 = 15;
}


When i compile it using gcc -c and create separate respective object file
-and try to link them it dosent give any errors as to "multiple declaration of variable" as of "variable a" in this case.

-And it gets comiled and linked successfully.
-also the "third printf" in file1.c prints the value of a=15 which is updated by file3.c.
-whereas its nowhere specified in file3.c that variable "a is an exterm variable"
in that case file1.c would printf the value of a1=15;
-so.................???????????????????????


Regards
Tanvir


Moved to High Level Programming Forum. FPMurphy

Last edited by vino; 07-24-2008 at 06:36 AM.. Reason: added code tags
 

10 More Discussions You Might Find Interesting

1. Programming

extern for functions

Hi, Please let me know if the extern keyword is necessary for using functions which is defined and declared in another file and and used in a different file where both these files are linked together. thanks (8 Replies)
Discussion started by: naan
8 Replies

2. Linux

Problem mounting extern hd (fedora 9)

Hi there, I'm having a bit of a strange problem which I would appreciate some help with. The Problem: I have two external hard drives, but I'm borrowing one off my parents to copy data too (one of mine, which is identical to theirs - WD MyBook 300g - is on its way out). Fedora 9 recognizes... (3 Replies)
Discussion started by: lasthidingplace
3 Replies

3. UNIX for Dummies Questions & Answers

fetchmail and forward to an extern address

Hi, I'm searching for an solution for the following problem. I want fetch some mails via pop3 from a@a.com with fetchmail. That works perfectly. Now any incoming mail should forwarded to b@b.com via smtp obv. But I don't know how to configure that. All online tutorials describe forwarding to... (0 Replies)
Discussion started by: mcW
0 Replies

4. Shell Programming and Scripting

Insert a line including Variable & Carriage Return / sed command as Variable

I want to instert Category:XXXXX into the 2. line something like this should work, but I have somewhere the wrong sytanx. something with the linebreak goes wrong: sed "2i\\${n}Category:$cat\n" Sample: Titel Blahh Blahh abllk sdhsd sjdhf Blahh Blah Blahh Blahh Should look like... (2 Replies)
Discussion started by: lowmaster
2 Replies

5. Shell Programming and Scripting

How to define a variable with variable definition is stored in a variable?

Hi all, I have a variable say var1 (output from somewhere, which I can't change)which store something like this: echo $var1 name=fred age=25 address="123 abc" password=pass1234 how can I make the variable $name, $age, $address and $password contain the info? I mean do this in a... (1 Reply)
Discussion started by: freddy1228
1 Replies

6. Programming

segmentation fault for extern

Why this is happening when both of them compiled together and run? I am getting segmentation fault SIGSEGV. File1.c: int arr; File2.c: extern int *arr; int main() { arr = 100; } (3 Replies)
Discussion started by: royalibrahim
3 Replies

7. Red Hat

How to pass value of pwd as variable in SED to replace variable in a script file

Hi all, Hereby wish to have your advise for below: Main concept is I intend to get current directory of my script file. This script file will be copied to /etc/init.d. A string in this copy will be replaced with current directory value. Below is original script file: ... (6 Replies)
Discussion started by: cielle
6 Replies

8. Shell Programming and Scripting

[Solved] How to increment and add variable length numbers to a variable in a loop?

Hi All, I have a file which has hundred of records with fixed number of fields. In each record there is set of 8 characters which represent the duration of that activity. I want to sum up the duration present in all the records for a report. The problem is the duration changes per record so I... (5 Replies)
Discussion started by: danish0909
5 Replies

9. Programming

C header file and extern

In the header file data.h i got: const char ack_msg = "ack: received your msg\n"; In the code file server.c i got: extern const char ack_msg; And else it is only used in a function call: user$ grep ack_msg *c *h server.c:extern const char ack_msg; server.c: n = write(clientsfd,... (5 Replies)
Discussion started by: tornow
5 Replies

10. Programming

Extern keyward on function in C

I saw a header (.h) file with mixture of "regular" function declarations and other extern function declarations. As I was told all function declarations are implicitly external and the extern on functions declarations is superfluous. Here my focus is on function declaration, not variable yet. int... (2 Replies)
Discussion started by: yifangt
2 Replies
FBB::mlm(3bobcat)                                             OFoldStream manipulator                                            FBB::mlm(3bobcat)

NAME
FBB::mlm - Manipulator modifying left margins of OFoldStream objects SYNOPSIS
#include <bobcat/ofoldstream> or #include <bobcat/ofoldstreambuf> Linking option: -lbobcat DESCRIPTION
The mlm class implements a manipulator that can be inserted into OFoldStream objects to modify the stream's left margin by a requested amount. The request cannot result in a negative left margin value. If a negative left margin would be the arithmetic result of the request then left margin 0 will silently be used. Depending on the tab-setting of the OFoldStream the inserted value represents the number of blank space characters or the number of tab-characters that will be added to the left margin. The request will be processed at the next newline character or std::flush or std::endl manipulator that is inserted into the stream. If a line is still empty once an mlm object and a flush manipulator are inserted into the stream then the new left margin will be effective at the next word inserted into that line (cf., the example section below) A bad_cast exception is thrown when the manipulator is inserted into an ostream that is not using a OFoldStreambuf buffer. NAMESPACE
FBB All constructors, members, operators and manipulators, mentioned in this man-page, are defined in the namespace FBB. INHERITS FROM
- CONSTRUCTOR
o mlm(int addValue): The standard copy constructor is available. MEMBER FUNCTIONS
There are no public or protected member functions in this class. EXAMPLE
#include <iostream> #include <bobcat/ofoldstream> using namespace std; using namespace FBB; int main() { OFoldStream out(cout, 0, 80); out << "hello world (left margin is 0)" << mlm(4) << " " "this uses a 4 character wide left margin " << mlm(-10) << flush << "left margin -6 changed to 0, active on this line "; return 0; } FILES
bobcat/mlm - defines the class interface SEE ALSO
bobcat(7), manipulators(3bobcat), lm(3bobcat), ofoldstream(3bobcat) BUGS
None Reported. DISTRIBUTION FILES
o bobcat_3.01.00-x.dsc: detached signature; o bobcat_3.01.00-x.tar.gz: source archive; o bobcat_3.01.00-x_i386.changes: change log; o libbobcat1_3.01.00-x_*.deb: debian package holding the libraries; o libbobcat1-dev_3.01.00-x_*.deb: debian package holding the libraries, headers and manual pages; o http://sourceforge.net/projects/bobcat: public archive location; BOBCAT
Bobcat is an acronym of `Brokken's Own Base Classes And Templates'. COPYRIGHT
This is free software, distributed under the terms of the GNU General Public License (GPL). AUTHOR
Frank B. Brokken (f.b.brokken@rug.nl). libbobcat1-dev_3.01.00-x.tar.gz 2005-2012 FBB::mlm(3bobcat)
All times are GMT -4. The time now is 01:43 AM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy