03-08-2013
9 More Discussions You Might Find Interesting
1. Red Hat
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)
Discussion started by: nstarz
1 Replies
2. Shell Programming and Scripting
Hi,
I'm trying to use sed within a shell script (bash, running ubuntu). The command works fine from the command line, but when I use it within the script, rather than creating a file with the name I've specified, it creates one that ends with a question mark '?' when you use ls, e.g.... (3 Replies)
Discussion started by: jennykay
3 Replies
3. Shell Programming and Scripting
I have a script that runs ditto for me, and occasionally (if I exit the script while ditto is running in the background) it will leave an empty file named 0 in the script's directory. The next time I run the script, it generates incorrect data because of this file. I know I can easily insert a... (1 Reply)
Discussion started by: reid
1 Replies
4. Shell Programming and Scripting
I have a script that runs ditto for me, and occasionally (if I exit the script while ditto is running in the background) it will leave an empty file named 0 in the script's directory. The next time I run the script, it generates incorrect data because of this file. I know I can easily insert a... (1 Reply)
Discussion started by: reid
1 Replies
5. UNIX for Advanced & Expert Users
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)
Discussion started by: Dedalus
3 Replies
6. UNIX for Dummies Questions & Answers
I'm using a script that does some modifications to data on disc and updates the database. The script (perl) uses STDOUT so the results are printed to the screen. I don't have permissions to modify the script. I want to capture the results in a file so I can see if errors occurred and also keep... (3 Replies)
Discussion started by: surib
3 Replies
7. Shell Programming and Scripting
I am new to Linux. Using latest version of Ubuntu.
I want to make a script that creates a 1GB file filled with zeros using dd and then formats the file as vfat with a label of "MYFILE".
If anyone can help me it would be appreciated. (9 Replies)
Discussion started by: paviter619
9 Replies
8. Red Hat
Hi,
I have created a test script like this :
# cat script1.sh
DAY=$(date +%d)
MONTH=$(date +%b)
YEAR=$(date +%Y)
BC01="Blast_BC01"
BC15="Blast_BC15"
DIR1="$MONTH$YEAR_$BC01"
DIR2="$MONTH$YEAR_$BC07"
DIR3="$MONTH$YEAR_$BC15"
if ;then
mkdir -p "$YEAR/$DIR3"
fi
#
When I... (5 Replies)
Discussion started by: anaigini45
5 Replies
9. Shell Programming and Scripting
I am new to Linux. Using latest version of Ubuntu.
I want to make a script that creates a 1GB file filled with zeros using dd and then formats the file as vfat with a label of "MYFILE".
If anyone can help me it would be appreciated. (1 Reply)
Discussion started by: amandasaza08
1 Replies
LOCK(2) System Calls Manual LOCK(2)
NAME
lockinit, lock, canlock, unlock - shared memory spin lock
SYNOPSIS
#include <lock.h>
void lockinit(void);
void lock(Lock *lk);
int canlock(Lock *lk);
void unlock(Lock *lk);
/* Alef only */
adt Lock
{
void lock(*Lock);
void unlock(*Lock);
int canlock(*Lock);
};
adt QLock
{
void lock(*Lock);
void unlock(*Lock);
int canlock(*Lock);
};
adt RWlock
{
void Rlock(*RWlock);
void Runlock(*RWlock);
void Wlock(*RWlock);
void Wunlock(*RWlock);
};
adt Ref
{
int inc(*Ref);
int dec(*Ref);
int ref(*Ref);
};
DESCRIPTION
These routines are used by processes sharing memory to synchronize using spin locks. Lockinit must be called before the first use of the
other routines. Lock blocks until the lock has been obtained. Canlock is non-blocking. It tries to obtain a lock and returns a non-zero
value if it was successful, 0 otherwise. Unlock releases a lock.
Alef
Alef locks have similar functionality, but no special initialization is required. The ADT Lock has functions lock, unlock, and canlock,
just like locks in C. QLocks have the same interface but are not spin locks; instead if the lock is taken QLock.lock will suspend execu-
tion of the calling task until it is released.
Although Locks are the more primitive lock, their use is discouraged and even erroneous for most purposes. For example, Locks cannot syn-
chronize between tasks in the same proc. Use QLocks instead.
RWlocks manage access to a data structure that has distinct readers and writers. RWlock.Rlock grants read access; RWlock.Runlock releases
it. RWlock.Wlock grants write access; RWlock.Wunlock releases it. There may be any number of simultaneous readers, but only one writer.
Moreover, if write access is granted no one may have read access until write access is released.
Refs manage reference counters. Ref.inc increments the counter and returns the old value; Ref.dec decrements the counter and returns the
new value. Ref.ref returns the current value.
SOURCE
/sys/src/liblock
SEE ALSO
rfork in fork(2)
LOCK(2)