|
|
Sponsored Content
Top Forums
Programming
I have no clue what's the point - fcntl() ?
Post 302075939 by atticus on Wednesday 7th of June 2006 04:47:25 PM
06-07-2006
I have no clue what's the point - fcntl() ?
hi, I need to know how to lock a file. I used the following code, but after executing the program the file 'write.txt' remined empty, and I have no idea why.Maybe I'm not using the corresponding syntax for blocking a file. But I deleted then the blocking part and the problem persisted.
see to code:
......
f=open("read.txt",O_RDONLY);
fcntl(f,F_SETLK);
read(f,buffer,sizeof(buffer));
g=open("write.txt",O_WRONLY);
write(g,buffer,sizeof(buffer));
close(g);
fcntl(f,F_UNLCK);
close(f);
.......
then I tried to replace open with fopen (so I use FILE *g of course, and fprintf()) but still nothing was in that file(write.txt).So I have no clue. If you got sometime pls say somethin'. I need to do this as soon as I can. You are welcomed to say somethin' smart
10x
see to code:
......
f=open("read.txt",O_RDONLY);
fcntl(f,F_SETLK);
read(f,buffer,sizeof(buffer));
g=open("write.txt",O_WRONLY);
write(g,buffer,sizeof(buffer));
close(g);
fcntl(f,F_UNLCK);
close(f);
.......
then I tried to replace open with fopen (so I use FILE *g of course, and fprintf()) but still nothing was in that file(write.txt).So I have no clue. If you got sometime pls say somethin'. I need to do this as soon as I can. You are welcomed to say somethin' smart
10x
Last edited by atticus; 06-07-2006 at 06:40 PM..
|
|
7 More Discussions You Might Find Interesting
1. UNIX for Advanced & Expert Users
Anyone know of a guide or instructions for Solaris
I got to configure a SBUS HBA to talk to a tape robot.
I have done this on a switch but not point to point.
just going HBA >>>>> TAPE Fibre simple two nodes
Kie (6 Replies)
Discussion started by: kie
6 Replies
2. Solaris
df shows that the filesystem is filling up and the usage is 94%.
However when I actually traverse to the directory I du shows only about
10% of the space occupied!
Below is the output of df and du:
>>>df -kh
/cbmdata/00 470M 393M 29M 94% /cbmdata/00
>>>/cbmdata/00>... (3 Replies)
Discussion started by: zombiezparadize
3 Replies
3. Programming
Hi,
Unless I am missing some serious differences in Mac and linux in terms of C programming, I dont know why this would happen. Please take a look at the following piece of code fragment:
bool add_input_to_db(Cons *new_data) {
// Set the attributes of the lock
struct flock fl =... (3 Replies)
Discussion started by: newhere
3 Replies
4. Programming
I have very simple client - server setup, where client connects, exchanges some messages with the server and then closes socket and exits. Everythink works OK, except when I am trying to change socket to be non-blocking AND the shell happens to be plain old Bourne. It runs no problem under ksh or... (3 Replies)
Discussion started by: migurus
3 Replies
5. Shell Programming and Scripting
Hello
I have a Perl script that works on non-darwin Mac OS X environments and I think I have narrowed down the issue to a file locking problem.
In other linux environments, the flock struct is defined differently. I have adjusted this via the reference for Mac OS X fcntl(2) man page. The... (4 Replies)
Discussion started by: flagman5
4 Replies
6. Shell Programming and Scripting
hi,
I would like to ask or is it possible to dump a hex using dd from starting point to end point just like the "xxd -s 512 -l 512 <bin file>"
I know the redirect hexdump -C but i can't figure it out the combination options of dd.
Hope someone can share their knowledge..
Thanks in... (3 Replies)
Discussion started by: jao_madn
3 Replies
7. Linux
Good evening, friends
I'm learning with a book: Programming Linux by Kurt Wall (Prentice Hall)
The code below could run in two windows (./lockit /tmp/foo in both for example). There is not problem with the read block (first byte) but when one, apply the write block while in the other is... (1 Reply)
Discussion started by: joe_cosmo
1 Replies
LEARN ABOUT REDHAT
vop_advlock
VOP_ADVLOCK(9) BSD Kernel Developer's Manual VOP_ADVLOCK(9) NAME
VOP_ADVLOCK -- advisory record locking SYNOPSIS
#include <sys/param.h> #include <sys/vnode.h> #include <sys/fcntl.h> #include <sys/lockf.h> int VOP_ADVLOCK(struct vnode *vp, caddr_t id, int op, struct flock *fl, int flags); DESCRIPTION
The arguments are: vp The vnode being manipulated. id The id token which is changing the lock. op The operation to perform (see fcntl(2)). fl Description of the lock. flags One of more of the following: F_RDLCK Shared or read lock. F_UNLCK Unlock. F_WRLCK Exclusive or write lock. F_WAIT Wait until lock is granted. F_FLOCK Use flock(2) semantics for lock. F_POSIX Use POSIX semantics for lock. This entry point manipulates advisory record locks on the file. Most file systems delegate the work for this call to lf_advlock(). RETURN VALUES
Zero is returned on success, otherwise an error is returned. SEE ALSO
fcntl(2), flock(2), vnode(9) AUTHORS
This manual page was written by Doug Rabson. BSD
June 30, 1999 BSD