01-30-2009
The first number in this group of 4 is for the special bits. '0' means nothing, '1' is the "sticky bit", '2' the "set group ID", and '4' the "set user ID" bit. '4' is probably the most used of those, as it changes execution of a program so that it doesn't run as the calling UID, but as the one of the file owner (same for the SGID bit, only with the group instead of the user). The passwd utility most often has this one set, as it requires root privileges to change the password file, but any user should be able to run it.
The effects of the "sticky bit" vary between platforms, and whether it's set on a file or directory. For files it originally was intended to tell the kernel "Keep this file in memory after it ended" so that subsequent calls wouldn't need to reread it from disk (not working in Linux). For directories it means "only the owner of this file may manipulate it", eg. on the /tmp dir, where every user may write, but others shouldn't be able to delete or modify a file there.
The first character in an ls -l output (in your example 'd') specifies the file type. '-' is a regular file, 'd' is a directory, 'c' is a character device, ....
HTH
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LEARN ABOUT OSF1
pthread_rwlock_trywrlock
pthread_rwlock_trywrlock(3) Library Functions Manual pthread_rwlock_trywrlock(3)
NAME
pthread_rwlock_trywrlock - Attempts to acquire a read-write lock for write access without waiting.
LIBRARY
DECthreads POSIX 1003.1c Library (libpthread.so)
SYNOPSIS
#include <pthread.h>
int pthread_rwlock_trywrlock(
pthread_rwlock_t *rwlock);
PARAMETERS
Address of the read-write lock object to acquire for write access.
DESCRIPTION
This routine attempts to acquire the read-write lock referenced by rwlock for write access. If any thread already holds that lock for write
access or read access, this routine fails and returns [EBUSY] and the calling thread does not wait for the lock to become available.
Results are undefined if the calling thread holds the read-write lock (whether for read or write access) at the time this routine is
called.
If the read-write lock object referenced by rwlock is not initialized, the results of calling this routine are undefined.
Realtime applications can encounter priority inversion when using read-write locks. The problem occurs when a high-priority thread acquires
a read-write lock that is about to be unlocked (that is, posted) by a low-priority thread, but the low-priority thread is preempted by a
medium-priority thread. This scenario leads to priority inversion in that a high-priority thread is blocked by lower-priority threads for
an unlimited period of time. During system design, realtime programmers must take into account the possibility of priority inversion and
can deal with it in a number of ways, such as by having critical sections that are guarded by read-write locks execute at a high priority,
so that a thread cannot be preempted while executing in its critical section.
RETURN VALUES
If an error condition occurs, this routine returns an integer value indicating the type of error. Possible return values are as follows:
Successful completion. The read-write lock could not be acquired for write access because it was already locked for write access or for
read access. The value specified by rwlock does not refer to an initialized read-write lock object. The current thread already owns the
read-write lock for write or read access.
ERRORS
None
RELATED INFORMATION
Functions: pthread_rwlock_init(3), pthread_rwlockattr_init(3), pthread_rwlock_rdlock(3), pthread_rwlock_wrlock(3), pthread_rwlock_unlock(3)
Manuals: Guide to DECthreads and Programmer's Guide
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pthread_rwlock_trywrlock(3)