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... (1 Reply)
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... (1 Reply)
Hi,
I have a ksh shell script that accesses databases to drop and create tables and the script also creates text files.
This shell script is accessed thru a java application that i would like to turn multi-user, but the only way that i can do that is if I can figure out a way to lock the shell... (2 Replies)
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... (3 Replies)
Hi,
I'm having a general query. If we do cat <file name> on a Ebcidic format file then many unknown characters are displayed in my screen.
Can we change the character set related to EBCIDIC in session level and apply the cat command on a EBCIDIC file? By doing so can we able to see the... (2 Replies)
Dear all,
I know this might be a simple and silly question but I am struggling with it
I have a long unix script and in a section of if I want to use a python script which should select all the files and run the script on it (as a whole)
the loop I have is selecting file by file and I dont know... (2 Replies)
I wrote two shell scripts in UNIX that renames the same file and scheduled them at the same time.
The following are the steps that I followed:-
1. I wrote 2 scripts named s1.sh and s2.sh, both trying to add “exec_” prefix to the name of the files present in a folder i which already don't start... (4 Replies)
Hi Forum.
I have the following challenge at work that I need to write a script for.
I have a file abc.txt with the following contents:
4560123456
4570987654
4580654321
I want to be able to search/replace in abc.txt - the first 4 characters anything starting with 4560 to 7777; 4570... (3 Replies)
I am trying to apply an awk action over multiple files in a directory. It is a simple action, I want to print out the 1st 2 columns (i.e. $1 and $2) in each tab-separated document and output the result in a new file *.pp
This is the awk that I have come up with so far, which is not giving me a... (6 Replies)
Hello Team-
we would like to implement an approach which has to write the log file simultaneously
when .sql file is executing by Unix process. At present,it is writing the log file
once the process is completed. I've tested the current process with the below
approaches and none of them... (1 Reply)
Discussion started by: Hima_B
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)