|
|
|
|
|
|||||||
| Forums | Portal | Register | Forum Rules | FAQ | Contribute | Members List | Arcade | Search | Today's Posts | Mark Forums Read |
| High Level Programming Post questions about C, C++, Java, SQL, and other programming languages here. |
More UNIX and Linux Forum Topics You Might Find Helpful
|
||||
| Thread | Thread Starter | Forum | Replies | Last Post |
| Post Shell programming: Question about source a file and read data from the file | ccwq | Shell Programming and Scripting | 3 | 08-04-2007 07:28 PM |
| How can i read a non text file in unix - ELF-64 executable object file - IA64 | alexcol | UNIX for Advanced & Expert Users | 4 | 07-20-2007 02:05 PM |
| questions about non-blocking read() | oddabe | High Level Programming | 3 | 05-23-2007 09:54 PM |
| How to read specific lines in a bulk file using C file Programming | rajan_ka1 | High Level Programming | 10 | 11-09-2005 11:29 PM |
| Blocking a Single IP | Phobos | UNIX for Dummies Questions & Answers | 4 | 04-27-2005 08:09 PM |
 |
|
|
Submit Tools | LinkBack | Thread Tools | Display Modes |
07-01-2006
|
|||
|
|||
|
Blocking file read
There are many processes writing to log files at random times (they are all programmed in different manners and can not be altered). I am writing a new c program which should read from the log files whenever they are updated. At the moment it is just spooling, waiting for a change in file size, but I really want to block until an update is made on one of the files.
Can this be done? I thought select or poll might work but apparently they arent much use when your using regular files. Also looked at using fifo's but seeing as I cant alter the original code it seems impossible. Any ideas? thanks 
|
| Forum Sponsor | ||
|
|
|
07-01-2006
|
||||
|
||||
|
There are two types of locking mechanisms: mandatory and advisory. Mandatory systems will actually prevent read()'s and write()'s to file. Several Unix systems support them.
To make an advisory lock in POSIX-systems fcntl must be used: Code:
#include <fcntl.h>
...
struct flock fl;
int fd;
fl.l_type = F_RDLCK; /* read lock */
fl.l_whence = SEEK_SET; /* beginning of file */
fl.l_start = 0; /* offset from l_whence */
fl.l_len = 0; /* length, 0 = to EOF */
fl.l_pid = getpid(); /* PID */
fd = open("filename", O_RDONLY);
fcntl(fd, F_SETLKW, &fl); /* set lock */
...
fl.l_type = F_UNLCK;
fcntl(fd, F_SETLK, &fl); /* unset lock */
|
|
| Thread Tools | |
| Display Modes | |
|
|
Linear Mode
