NAME¶

direvent.conf - configuration file for direvent(8).

DESCRIPTION¶

The configuration file consists of statements and comments.

There are three classes of lexical tokens: keywords, values, and separators. Blanks, tabs, newlines and comments, collectively called white space are ignored except as they serve to separate tokens. Some white space is required to separate otherwise adjacent keywords and values.

COMMENTS¶

Comments may appear anywhere where white space may appear in the configuration file. There are two kinds of comments: single-line and multi-line comments. Single-line comments start with # or // and continue to the end of the line:

# This is a comment
// This too is a comment

Multi-line or C-style comments start with the two characters /* (slash, star) and continue until the first occurrence of */ (star, slash).

Multi-line comments cannot be nested. However, single-line comments may well appear within multi-line ones.

STATEMENTS¶

pidfile /var/run/direvent.pid;

watcher {


    path /etc;


    event create;
}

VARIABLE EXPANSION¶

Arguments of some statements undergo variable expansion before use. During variable expansion, variable references found in string are replaced with the actual values of the corresponding variables.

A variable reference has the form $VAR or ${VAR}, where VAR is the variable name. The two forms are entirely equivalent. The form with curly braces is normally used if the variable name is immediately followed by an alphanumeric symbol, which will otherwise be considered part of it. This form also allows for specifying the action to take if the variable is undefined or expands to an empty value:

${VARIABLE:-WORD}

Use Default Values. If VARIABLE is unset or null, the expansion of WORD is substituted. Otherwise, the value of VARIABLE is substituted.

${VARIABLE:=WORD}

Assign Default Values. If VARIABLE is unset or null, the expansion of WORD is assigned to the variable. The value of VARIABLE is then substituted.

${VARIABLE:?WORD}

Display Error if Null or Unset. If VARIABLE is null or unset, the expansion of WORD (or a message to that effect if WORD is not present) is output to the current logging channel. Otherwise, the value of VARIABLE is substituted.

${VARIABLE:+WORD}

Use Alternate Value. If VARIABLE is null or unset, nothing is substituted, otherwise the expansion of WORD is substituted.

Two kinds of variables take part in variable expansion: environment variables and macro variables. The latter are special variable-like entities defined by direvent to carry information about the event and its target file:

file

Name of the file covered by the event.

genev_code

Generic (system-independent) event code. It is a bitwise OR of the event codes represented as a decimal number.

genev_name

Generic event name. If several generic events are reported simultaneously, the value of this variable is a list of event names separated by space characters. Each name corresponds to a bit in genev_code.

self_test_pid

The PID of the external command started with the --self-test (-T) option. If direvent is started without this option, this variable is not defined.

sysev_code

System-dependent event code. It is a bitwise OR of the event codes represented as a decimal number.

sysev_name

System-dependent event name. If several events are reported, the value of this variable is a list of event names separated by space characters. Each name corresponds to a bit in sysev_code. See the section SYSTEM DEPENDENCIES in direvent(8), for a list of system-dependent event names.

GENERAL SETTINGS¶

user NAME;

Sets the user to run as. NAME must be a name of an existing user.

foreground BOOL;

Run in foreground.

pidfile FILE;

Upon successful startup store the PID of the daemon process in FILE.

debug NUMBER;

Set debug level. Valid NUMBER values are 0 (no debug) to 3 (maximum verbosity).

LOGGING¶

While connected to the terminal direvent outputs its diagnostics and debugging messages to the standard error. After disconnecting from the controlling terminal it closes the first three file descriptors and directs all its output to the syslog. When running in foreground mode, its messages are sent both to the standard error and to the syslog.

The following configuration statement controls the syslog output:

syslog {


facility STRING;
tag STRING;
print-priority BOOL;


}

The statements are:

facility STRING;

Set syslog facility. STRING is one of the following: user, daemon, auth or authpriv, mail, cron, local0 through local7 (case-insensitive), or a facility number.

tag STRING;

Tag syslog messages with STRING. Normally the messages are tagged with the program name.

print-priority BOOL;

Prefix each message with its priority.

An example syslog statement:

syslog {


    facility local0;


    print-priority yes;
}

ENVIRONMENT¶

By default the command inherits the environment of direvent augmented with the following variables:

DIREVENT_SYSEV_CODE

The system-dependent event code (see the sysev_code macro variable).

DIREVENT_SYSEV_NAME

The system-dependent event name or names (see the sysev_name macro variable).

DIREVENT_GENEV_CODE

The generic event code (see the genev_code macro variable).

DIREVENT_GENEV_NAME

The generic event name or names (see the genev_name macro variable).

DIREVENT_FILE

The name of the affected file relative to the current working directory (see the file macro variable).

This environment can be further modified, using the environ configuration statement:

environ {


clear;
keep PATTERN;
keep"NAME=VALUE";
set "NAME=VALUE";
eval EXPR;
unset PATTERN;
unset "NAME=VALUE";


}

Statements inside the environ block define operations that modify the environment. Their arguments undergo variable expansion. The clear statement is executed first. Then, keep statements are applied, in order of their appearance. Finally, set and unset statements are applied in order of their appearance in the configuration.

clear

Clears the environment by removing (unsetting) all variables, except those listed in keep statements, if such are given (see below). This statement is always executed first.

keep PATTERN

Declares variables matching PATTERN (a globbing pattern) as exempt from clearing. This statement implies clear.

keep "NAME=VALUE"

Retains NAME in the environment only if it has the value VALUE. Notice double-quotes.

set "NAME=VALUE"

Assigns VALUE to the environment variable NAME. The value is subject to variable expansion using the same syntax as in shell. The set, eval, and unset (see below) statements are executed in order of their appearance.

eval EXPR

Perform variable expansion on EXPR and discard the result. This is useful for side-effects.

unset PATTERN

Unset environment variables matching PATTERN.

unset "NAME=VALUE"

Unset environment variable NAME if it has the given VALUE.

WATCHER¶

The watcher statement configures a single event watcher. A watcher can control several events in multiple pathnames. Any number of watcher statements is allowed in the configuration file, each one of them declaring a separate watcher.

watcher {


path PATHNAME [recursive [NUMBER]];
file STRING-LIST;
event STRING-LIST;
command STRING;
user NAME;
timeout NUMBER;
option STRING-LIST;
environ {ENV-SPEC}


}

The statements within a watcher block are:

path PATHNAME [recursive [NUMBER]];

Defines a pathname to watch. PATHNAME must be the name of an existing directory in the file system. The watcher will watch events occurring for all files within that directory. If the optional recursive clause is specified, this directory will be watched recursively, i.e. when any subdirectory is created in it, direvent will set up a watcher for files in this subdirectory. This new watcher will be an exact copy of the parent watcher, excepting for the pathnames. The optional NUMBER parameter defines a cut-off nesting level for recursive watching. If supplied, the recursive behaviour will apply only to the directories that are nested below that level.

Any number of path statements can appear in a watcher block. At least one path must be defined.

file STRING-LIST;

Selects which files are eligible for monitoring. The argument is a list of globbing patterns (in the sense of fnmatch(3)) and/or extended regular expressions ( regex(7)) one of which the file name must match in order for the watcher to act on it. Regular expressions must be surrounded by a pair of slashes, optionally followed by the following flags:

event STRING-LIST;

Configures the filesystem events to watch for in the directories declared by the path statements. The argument is a list of event names. Both generic and system-dependent event names are allowed. Multiple event statements accumulate. A missing event statements means watch all events. For example:

event (open,delete);

command STRING;

Defines a command to execute on event. STRING is a command line just as you would type it in sh(1). It may contain macro variables, which will be expanded prior to execution. For example:

command "/bin/prog -event $genev_name -file $file";

See the section HANDLER ENVIRONMENT in direvent(8), for a detailed discussion of how the command is executed.

user STRING;

Run command as this user.

timeout NUMBER;

Terminate the command if it runs longer than NUMBER seconds. The default is 5 seconds.

option STRING-LIST;

A list of additional options. The following options are defined:

environ {ENV-SPEC}

Modify command environment. See the section ENVIRONMENT, for a discussion of sub-statements in ENV-SPEC. This statement applies to the environment, modified by the global environ statement, if any.

SEE ALSO¶

direvent(8).

COPYRIGHT¶

Copyright © 2012-2021 Sergey Poznyakoff
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law.