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 struct is defined as:
Code:
struct flock {
off_t l_start; /* starting offset */
off_t l_len; /* len = 0 means until end of file */
pid_t l_pid; /* lock owner */
short l_type; /* lock type: read/write, etc. */
short l_whence; /* type of l_start */
};
I am using the flock as the following:
Code:
my $msg = fcntl( $LOCKF, F_SETLK, pack("lliss",0,0,0,F_WRLCK,0) ) or die "Something wrong: $!";
The adjustment works on a separate test script that I extracted parts of the script out for testing. However when I deploy it to the real script, it doesnt work anymore. I then did a trial-error sequence and found that after certain 'additions' to the code, anything I add, such as a simple print "hello" statement, would result in the fcntl line not working. (The error outputted is Invalid Argument supplied).
Is it because the offset, len, l_whence are not defined correctly?
Please help if you are familiar with Mac OSX. I downloaded OpenSSH for a newer version of SSH than what comes with OS 10.1. What a mistake! Now every time I try to make a connection to my remote server I get an message that ssh was built against version such and such and I have version such and... (2 Replies)
I finally broke down and decided to buy a new piece of hardware. I think I made the right decision when I chose an Apple iBook - OSX is incredible! I haven't used a Mac since System7.5, and 10.2 is just blowing me away!
Best of all, it's easy to use for people who are not used to Mac, but if I... (5 Replies)
I'm currently looking for an emulation program that would allow me to open and run osx app.s and programs on a windows xp based system.
if not is there a unix/linux/lindows program that may do the same? (3 Replies)
Hello,
I am trying to write a simple program with functions in the ncurses library, on a Mac running OSX 10.2.8, with the compiler and libraries that were included in the Dec 2002 Developer's tools release (the last one that runs on Jaguar, as far as I know). When I try to compile, I get... (2 Replies)
Hi,
I have installed bash 3.2 via darwin ports, however when I try and change the shell i.e. chsh -s /opt/local/bin/bash is says its a non-standard shell? but if i run ./bash i get a new bash prompt with version 3.2?
Thanks (3 Replies)
I've got this problem. My computers and external hard drives are converting many of my files to a Unix Executable File which has a grey terminal looking icon. I don't understand what is causing this to happen. It is happening to a large number of my image file of different formats and also... (1 Reply)
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)
Hey guyz,
Is it possible to build user-mode linux kernel on MAC OSX?
Please I need a reply asap as I have an assignment that I need to do.
Thanks!
Adel (1 Reply)
Discussion started by: aje02
1 Replies
LEARN ABOUT DEBIAN
flock
FLOCK(1) User Commands FLOCK(1)NAME
flock - manage locks from shell scripts
SYNOPSIS
flock [-sxon] [-w timeout] lockfile [-c] command...
flock [-sxon] [-w timeout] lockdir [-c] command...
flock [-sxun] [-w timeout] fd
DESCRIPTION
This utility manages flock(2) locks from within shell scripts or the command line.
The first and second forms wraps the lock around the executing a command, in a manner similar to su(1) or newgrp(1). It locks a specified
file or directory, which is created (assuming appropriate permissions), if it does not already exist.
The third form is convenient inside shell scripts, and is usually used the following manner:
(
flock -n 9 || exit 1
# ... commands executed under lock ...
) 9>/var/lock/mylockfile
The mode used to open the file doesn't matter to flock; using > or >> allows the lockfile to be created if it does not already exist, how-
ever, write permission is required; using < requires that the file already exists but only read permission is required.
By default, if the lock cannot be immediately acquired, flock waits until the lock is available.
OPTIONS -s, --shared
Obtain a shared lock, sometimes called a read lock.
-x, -e, --exclusive
Obtain an exclusive lock, sometimes called a write lock. This is the default.
-u, --unlock
Drop a lock. This is usually not required, since a lock is automatically dropped when the file is closed. However, it may be
required in special cases, for example if the enclosed command group may have forked a background process which should not be hold-
ing the lock.
-n, --nb, --nonblock
Fail (with an exit code of 1) rather than wait if the lock cannot be immediately acquired.
-w, --wait, --timeout seconds
Fail (with an exit code of 1) if the lock cannot be acquired within seconds seconds. Decimal fractional values are allowed.
-o, --close
Close the file descriptor on which the lock is held before executing command. This is useful if command spawns a child process
which should not be holding the lock.
-c, --command command
Pass a single command to the shell with -c.
-h, --help
Print a help message.
AUTHOR
Written by H. Peter Anvin <hpa@zytor.com>.
COPYRIGHT
Copyright (C) 2003-2006 H. Peter Anvin.
This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICU-
LAR PURPOSE.
SEE ALSO flock(2)AVAILABILITY
The flock command is part of the util-linux package and is available from ftp://ftp.kernel.org/pub/linux/utils/util-linux/.
util-linux February 2006 FLOCK(1)