Manual Reference Pages - RWPOLLEXEC (8)
rwpollexec - Monitor a directory for files and execute a command on them
rwpollexec --incoming-directory=DIR_PATH --command=COMMAND
[--timeout=SIGNAL,SECS [--timeout=SIGNAL,SECS ...]]
| --log-directory=DIR_PATH [--log-basename=LOG_BASENAME]
[--pidfile=FILE_PATH] [--no-chdir] [--no-daemon]
rwpollexec is a daemon that monitors a directory for incoming
files, and then runs a given command on each file. If the command
runs successfully on a file, the file is either moved to an archive
directory or deleted. If the command runs unsuccessfully or is
terminated by a signal, the file is moved to an error directory.
rwpollexec allows a single command to be specified. If you need
to run multiple commands on a file, create a script to run these
commands and have rwpollexec run the script.
The --simultaneous switch specifies the maximum number of
invocations of COMMAND that rwpollexec will run concurrently.
The default is one, which causes rwpollexec to process the files
one at a time.
If there is a possibility that the command will hang and cause
rwpollexec to stop processing files, you may wish to specify that
rwpollexec send a signal to the command after it has been running
for some number of seconds by using the --timeout switch. This
switch may be repeated to send different signals after various times.
When rwpollexec is signaled to exit, it waits for all running
commands to terminate before exiting. If a command has hung,
rwpollexec will not exit until that command is killed, or
rwpollexec itself is sent a SIGKILL.
Option names may be abbreviated if the abbreviation is unique or is an
exact match for an option. A parameter to an option may be specified
as --arg=param or --arg param, though the first form is
required for options that take optional parameters.
One of the following logging switches is required:
Monitor this directory for new files to handle. DIR_PATH must be a
complete directory path. For each new file in this directory,
rwpollexec will run the command specified by the --command
switch. rwpollexec ignores any files in this directory that are
empty or whose names begin with a dot (.). In addition, new files
will only be considered when their size is constant for one
polling-interval after they are first noticed. This switch is
Run COMMAND on each file noticed in the directory specified by
--incoming-directory. Each occurrence of the string %s in
COMMAND will be replaced with the full path to the file, and
each occurrence of %% will be replaced with %. If any other
character follows %, rwpollexec exits with an error. If the
exit status of COMMAND is zero, rwpollexec will delete the file
unless the --archive-directory switch is specified, in which case
rwpollexec moves the file to that directory. If the command exits
with a non-zero status or is terminated by a signal, rwpollexec
moves the file to the directory specified by --error-directory.
This switch is required.
COMMAND is interpreted by the shell used by rwpollexec. When
the SILK_RWPOLLEXEC_SHELL environment variable is set, its value
will be used as the shell. Otherwise, rwpollexec determines the
shell as described in the FILES section. Any output on stdout
or stderr from COMMAND will appear in the log when the log
messages are being written to a local log file.
Move to this directory files where COMMAND either runs
unsuccessfully (i.e., has a non-zero exit status) or terminates by a
signal. DIR_PATH must be a complete directory path. This switch
Move to this directory the files where COMMAND runs successfully
(i.e., has an exit status of zero). DIR_PATH must be a complete
directory path. If this switch is not supplied, rwpollexec will
delete these files instead. When the --flat-archive switch is also
provided, incoming files are moved into the top of DIR_PATH; when
--flat-archive is not given, each file is moved to a subdirectory
based on the current local time:
DIR_PATH/YEAR/MONTH/DAY/HOUR/. Removing files from the
archive-directory is not the job of rwpollexec; the system
administrator should implement a separate process to clean this
When archiving input files via the --archive-directory switch, move
the files into the top of the archive-directory, not into
subdirectories of the archive-directory. This switch has no effect if
--archive-directory is not also specified. This switch can be used
to allow another process to watch for new files appearing in the
Allow a maximum of NUM commands to be executed simultaneously. The
default is one, which allows only one command to be run at a time.
The maximum value allowed for this switch is 50.
Send SIGNAL to the running command if it has been executing for
SECS seconds. SIGNAL can be a signal name, with or without a
SIG prefix, or a signal number. A list of signals can be
determined by running the command kill -l. This switch may be
repeated to send different signals after various amounts of time.
Configure rwpollexec to check the incoming directory for new
files every NUM seconds. The default polling interval is 15
The following set of switches is optional:
Specify the destination where logging messages are written. When
DESTINATION begins with a slash /, it is treated as a file
system path and all log messages are written to that file; there is no
log rotation. When DESTINATION does not begin with /, it must
be one of the following strings:
Messages are not written anywhere.
Messages are written to the standard output.
Messages are written to the standard error.
Messages are written using the syslog(3) facility.
Messages are written to the syslog facility and to the standard error
(this option is not available on all platforms).
Use DIR_PATH as the directory where the log files are written.
DIR_PATH must be a complete directory path. The log files have the
where YYYYMMDD is the current date and LOG_BASENAME is the
application name or the value passed to the --log-basename switch
when provided. The log files are rotated: At midnight local time, a
new log is opened, the previous file is closed, and the command
specified by --log-post-rotate is invoked on the previous days log
file. (Old log files are not removed by rwpollexec; the
administrator should use another tool to remove them.) When this
switch is provided, a process-ID file (PID) is also written in this
directory unless the --pidfile switch is provided.
Use FILE_PATH as the complete path to the log file. The log file
is not rotated.
Set the severity of messages that will be logged. The levels from
most severe to least are: emerg, alert, crit, err,
warning, notice, info, debug. The default is info.
Set the facility that syslog(3) uses for logging messages. This
switch takes a number as an argument. The default is a value that
corresponds to LOG_USER on the system where rwpollexec is
running. This switch produces an error unless
--log-destination=syslog is specified.
Use LOG_BASENAME in place of the application name in the name of
log files in the log directory. See the description of the
--log-directory switch. This switch does not affect the name of
the process-ID file.
Run COMMAND on the previous days log file after log rotation.
When this switch is not specified, the previous days log file is
compressed with gzip(1). When the switch is specified and
COMMAND is the empty string, no action is taken on the log file.
Each occurrence of the string %s in COMMAND will be replaced
with the full path to the log file, and each occurrence of %% will
be replaced with %. If any other character follows %,
rwpollexec exits with an error. Specifying this switch without
also using --log-directory is an error.
Set the complete path to the file in which rwpollexec writes its
process ID (PID) when it is running as a daemon. No PID file is
written when --no-daemon is given. When this switch is not
present, no PID file is written unless the --log-directory switch
is specified, in which case the PID is written to
Do not change directory to the root directory. When rwpollexec
becomes a daemon process, it changes its current directory to the root
directory so as to avoid potentially running on a mounted file system.
Specifying --no-chdir prevents this behavior, which may be useful
during debugging. The application does not change its directory when
--no-daemon is given.
Force rwpollexec to run in the foreground---it does not become a
daemon process. This may be useful during debugging.
Print the available options and exit.
Print the version number and information about how SiLK was
configured, then exit the application.
The shell to use for executing commands. If this variable is not set,
rwpollexec tests the list of shells specified in FILES to find
a shell that uses a member of the execl(3) family of functions to
run the command. More details are available in the BUGS section.
Shells that rwpollexec may use to invoke the command specified by
--command. The shell specified in SILK_RWPOLLEXEC_SHELL is always
used when that variable is set. Otherwise, rwpollexec checks the
list of shells to find one that uses execl(3) to invoke the
command. When a suitable shell is not found, rwpollexec uses
/bin/sh. See BUGS for additional information.
rwpollexec uses a subshell to execute the command specified as the
argument to --command. How the subshell invokes the command is
important when the --timeout switch is specified. Many shells use
a member of execl(3) family of functions to invoke the command,
which causes the commands process to replace the shell process. For
these shells, signals sent by rwpollexec are received by the
command process directly. However, some shells use a combination of
fork(2) and wait(2) to invoke the command. In these shells, the
signal is received by the subshell instead of the command, and this
can lead to undesirable or unreliable behavior. When the
SILK_RWPOLLEXEC_SHELL environment variable is set, rwpollexec uses
that shell regardless of how it invokes its command, though if the
specified shell uses fork(2), rwpollexec will emit a warning to
the standard error and to the log. When SILK_RWPOLLEXEC_SHELL is not
set, rwpollexec attempts to find a shell that uses execl(3). If
rwpollexec fails to find a suitable shell, it uses /bin/sh and
emits and error to standard error and to the log. The list of shells
rwpollexec checks are specified in the FILES section.
rwpollexec is unable to tell the difference between a command
returning a non-zero exit status and a command that fails because the
command does not exist or is malformed. Both appear as a failed
command with a non-zero exit status. The shell may emit messages that
explain why a command has failed. In these instances, these messages
will appear in the log.
silk(7), kill(1), gzip(1), syslog(3), fork(2),
|SiLK 18.104.22.168 ||RWPOLLEXEC (8) ||2016-04-05 |
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