I have a set of scripts to do software releases to remote machines which uses ftp. I'm having a problem getting 'lost connection' messages.
What I wanted to ask is, does ftp employ some sort of file locking if two ftp processes are trying to copy the same file at the same time? & if so could... (2 Replies)
Hi,
Simple question but I just need to confirm the answer:
If two or more processes attempt to move the same file at exactly the same time, will unix internal file locking allow only one of the processes to access the file?
Many thanks
Helen :) (2 Replies)
We want to lock a file, during a program(pgm1) execution(until the execution of the program is completed), so that other program(pgm2) can't read/edit that file, until execution of earlier program(pgm1) is completed. How can this be achieved thru shell scripting...
we tried chmod +l option, but... (1 Reply)
how do i implement file locking in unix?
example if i want to update a file, i would like to use file locking. how do i implement it?
i am using shell script
thanks (3 Replies)
how to ensure all files are being locked while updateing some files?
example when i want to update the password and shadow file in unix. how do i implement file locking??
please advice
thanks (2 Replies)
i am working on a device runnin on linux....i have configured the samba server in the device such that my windows PC can access a shared folder in the device. Also in the device i am runnin some programs which access the files in this shared folder. What i want to know is whether there is any way i... (1 Reply)
Hi everyone! I'm totally new to Unix/Linux. In my last job I was able to be exposed a little bit by using unbuntu desktop for 11 months and also the xemacs editor. I basically know nothing and I'm totally interested in ditching the Microsoft Environment.
I would like to build a file server... (1 Reply)
Discussion started by: jtaylor69
1 Replies
LEARN ABOUT XFREE86
lockf
LOCKF(3) Linux Programmer's Manual LOCKF(3)NAME
lockf - apply, test or remove a POSIX lock on an open file
SYNOPSIS
#include <unistd.h>
int lockf(int fd, int cmd, off_t len);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
lockf():
_XOPEN_SOURCE >= 500
|| /* Glibc since 2.19: */ _DEFAULT_SOURCE
|| /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
DESCRIPTION
Apply, test or remove a POSIX lock on a section of an open file. The file is specified by fd, a file descriptor open for writing, the
action by cmd, and the section consists of byte positions pos..pos+len-1 if len is positive, and pos-len..pos-1 if len is negative, where
pos is the current file position, and if len is zero, the section extends from the current file position to infinity, encompassing the
present and future end-of-file positions. In all cases, the section may extend past current end-of-file.
On Linux, lockf() is just an interface on top of fcntl(2) locking. Many other systems implement lockf() in this way, but note that POSIX.1
leaves the relationship between lockf() and fcntl(2) locks unspecified. A portable application should probably avoid mixing calls to these
interfaces.
Valid operations are given below:
F_LOCK Set an exclusive lock on the specified section of the file. If (part of) this section is already locked, the call blocks until the
previous lock is released. If this section overlaps an earlier locked section, both are merged. File locks are released as soon as
the process holding the locks closes some file descriptor for the file. A child process does not inherit these locks.
F_TLOCK
Same as F_LOCK but the call never blocks and returns an error instead if the file is already locked.
F_ULOCK
Unlock the indicated section of the file. This may cause a locked section to be split into two locked sections.
F_TEST Test the lock: return 0 if the specified section is unlocked or locked by this process; return -1, set errno to EAGAIN (EACCES on
some other systems), if another process holds a lock.
RETURN VALUE
On success, zero is returned. On error, -1 is returned, and errno is set appropriately.
ERRORS
EACCES or EAGAIN
The file is locked and F_TLOCK or F_TEST was specified, or the operation is prohibited because the file has been memory-mapped by
another process.
EBADF fd is not an open file descriptor; or cmd is F_LOCK or F_TLOCK and fd is not a writable file descriptor.
EDEADLK
The command was F_LOCK and this lock operation would cause a deadlock.
EINVAL An invalid operation was specified in cmd.
ENOLCK Too many segment locks open, lock table is full.
ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).
+----------+---------------+---------+
|Interface | Attribute | Value |
+----------+---------------+---------+
|lockf() | Thread safety | MT-Safe |
+----------+---------------+---------+
CONFORMING TO
POSIX.1-2001, POSIX.1-2008, SVr4.
SEE ALSO fcntl(2), flock(2)
locks.txt and mandatory-locking.txt in the Linux kernel source directory Documentation/filesystems (on older kernels, these files are
directly under the Documentation directory, and mandatory-locking.txt is called mandatory.txt)
COLOPHON
This page is part of release 4.15 of the Linux man-pages project. A description of the project, information about reporting bugs, and the
latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.
GNU 2017-09-15 LOCKF(3)