file lock

9 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

Lock file creation

Hi, Please let me know how these steps are creating a lock file using echo " ". LOCK_FILE=${LOG_DIR}/${DBNAME}_MD.lock # create lock file if then echo "Another process is running already. Will terminate this one." >> ${LOG_FILE} 2>&1 echo "If the lock file is not needed, please...

2. Shell Programming and Scripting

Lock file creates with '?'

Hi, I am trying to create a lock file with the following code but for some reason after file is created it has wrong name "PASP?.lock??" Please let us know how to get rid of these '??' from file name and from where they are coming? #!/bin/ksh...

3. UNIX for Advanced & Expert Users

Testing privileges -lock lockfile /var/lock/subsys/..- Permission denied

Hi all, I have to test some user priviliges. The goal is to be sure that an unauthorized user can't restart some modules (ssh, mysql etc...). I'm trying to automate it with a shell script but in same cases I got the syslog broadcast message. Is there any way to simply get a return code...

4. Red Hat

Security Question: Lock after invalid login, Session Lock and Required Minimum Password Length

Hello all, If anyone has time, I have a few questions: How do I do the following in Linux. We are using Red Hat and Oracle Enterprise Linux, which is based on Red Hat too. 1. How to lock the account after a few (like 3) invalid password attempts? 2. How do you lock a screen after 30...

5. Red Hat

lock the file in linux

Hi, I want to lock the file in linux and the file cannot be edit or modify by other .I know in perl, there is function flock , but it is not worked. The file can be modifed and edit even if it is locked by flock . Any other way to lock the file and so other cannot edit or modifed it ???? Any...

6. UNIX for Dummies Questions & Answers

Lock File

Hi, We have a lock file being created called lck8c0001 created in Unixware 2.1.2. This is locking a printer. According to some websites, 8c0001 relates to the device name. How does one link 8c0001 to those devices listed in the /dev folder? I have done a ps -lp for all printers and have...

7. UNIX for Dummies Questions & Answers

how to lock keyboard without using lock command

how can I lock my keyboard while I'm away from the computer without using lock command. What other commands gives me the option to lock keyboard device? thanks

8. UNIX for Dummies Questions & Answers

lock file!

I found a lock file like this lrwxrwxr-x 1 sskb apollo 16 Oct 22 22:00 lock -> hostname:2747 (pl. note that hostname is a number like 123.4.5.6) but this was not shown in the file manager eventhough I had selected to show the hidden files. I could not even read the...

9. UNIX for Dummies Questions & Answers

How to lock a file in unix?

We wish to keep a sequence number in a file. When someone wants to get the next sequence number we need to lock the file, get the next number and increment it by one. How do you do that? I know how to get the number and increment it but how do I lock the file and test that it is locked or not...

LEARN ABOUT BSD

flock

FLOCK(2)							System Calls Manual							  FLOCK(2)

NAME

       flock - apply or remove an advisory lock on an open file

SYNOPSIS

       #include <sys/file.h>

       #define	 LOCK_SH   1	/* shared lock */
       #define	 LOCK_EX   2	/* exclusive lock */
       #define	 LOCK_NB   4	/* don't block when locking */
       #define	 LOCK_UN   8	/* unlock */

       flock(fd, operation)
       int fd, operation;

DESCRIPTION

       Flock applies or removes an advisory lock on the file associated with the file descriptor fd.  A lock is applied by specifying an operation
       parameter that is the inclusive or of LOCK_SH or LOCK_EX and, possibly, LOCK_NB.  To unlock an existing lock operation should be LOCK_UN.

       Advisory locks allow cooperating processes to perform consistent operations on files, but do not guarantee consistency (i.e., processes may
       still access files without using advisory locks possibly resulting in inconsistencies).

       The  locking  mechanism allows two types of locks: shared locks and exclusive locks.  At any time multiple shared locks may be applied to a
       file, but at no time are multiple exclusive, or both shared and exclusive, locks allowed simultaneously on a file.

       A shared lock may be upgraded to an exclusive lock, and vice versa, simply by specifying the appropriate lock type;  this  results  in  the
       previous lock being released and the new lock applied (possibly after other processes have gained and released the lock).

       Requesting  a lock on an object that is already locked normally causes the caller to be blocked until the lock may be acquired.	If LOCK_NB
       is included in operation, then this will not happen; instead the call will fail and the error EWOULDBLOCK will be returned.

NOTES

       Locks are on files, not file descriptors.  That is, file descriptors duplicated through	dup(2)	or  fork(2)  do  not  result  in  multiple
       instances of a lock, but rather multiple references to a single lock.  If a process holding a lock on a file forks and the child explicitly
       unlocks the file, the parent will lose its lock.

       Processes blocked awaiting a lock may be awakened by signals.

RETURN VALUE

       Zero is returned if the operation was successful; on an error a -1 is returned and an error code is left in the global location errno.

ERRORS

       The flock call fails if:

       [EWOULDBLOCK]	   The file is locked and the LOCK_NB option was specified.

       [EBADF]		   The argument fd is an invalid descriptor.

       [EINVAL] 	   The argument fd refers to an object other than a file.

SEE ALSO

       open(2), close(2), dup(2), execve(2), fork(2)

4.2 Berkeley Distribution					   May 22, 1986 							  FLOCK(2)

UNIX for Advanced & Expert Users