halockrun(1m) [opensolaris man page]

halockrun(1M)						  System Administration Commands					     halockrun(1M)

NAME

       halockrun - run a child program while holding a file lock

SYNOPSIS

       /usr/cluster/bin/halockrun [-nsv] [-e exitcode] lockfilename
       prog [args]

DESCRIPTION

       The halockrun utility provides a convenient means to claim a file lock on a file and run a program while holding that lock. As this utility
       supports script locking, this utility is useful when programming in scripting languages such as the Bourne shell. See sh(1).

       halockrun opens the file lockfilename and claims an exclusive mode file lock on the entire file. See fcntl(2) fcntl(2)). Then it  runs  the
       program	prog  with arguments args as a child process and waits for the child process to exit. When the child exits, halockrun releases the
       lock, and exits with the same exit code with which the child exited.

       The overall effect is that the child prog is run as a critical section, and that this critical section is well-formed, in  that	no  matter
       how the child terminates, the lock is released.

       If the file lockfilename cannot be opened or created, then halockrun prints an error message on stderr and exits with exit code 99.

       You  can  run  this command in the global zone or in a non-global zone. The command affects only the global or non-global zone in which you
       issue the command.

OPTIONS

       The following options are supported:

       -e exitcode		   Normally, errors detected by halockrun exit with exit code 99. The -e option provides a means  to  change  this
				   special exit code to a different value.

       -n			   The	lock  should be requested in non-blocking mode: if the lock cannot be granted immediately, halockrun exits
				   immediately, with exit code 1, without running prog. This behavior is not affected by the -e option.

				   Without the -n option, the lock is requested in blocking mode, thus, the halockrun utility blocks  waiting  for
				   the lock to become available.

       -s			   Claim the file lock in shared mode, rather than in exclusive mode.

       -v			   Verbose output, on stderr.

EXIT STATUS

       Errors  detected  by halockrun itself, such that the child process was never started, cause halockrun to exit with exit code 99. (This exit
       code value can be changed to a different value using the -e option. See OPTIONS.

       Otherwise, halockrun exits with the same exit code with which the child exited.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Availability		     |SUNWscu			   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Evolving			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       fcntl(2), attributes(5)

Sun Cluster 3.2 						    10 Apr 2006 						     halockrun(1M)

Check Out this Related Man Page

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)

Linux and UNIX Man Pages

halockrun(1m) [opensolaris man page]

Check Out this Related Man Page