NAME

logger — log messages

SYNOPSIS

logger [-i] [-f file] [-p priority] [-t tag] [string...]

DESCRIPTION

The logger utility shall send messages to an implementation-defined logging facility, which may log them in an implementation-defined system log, write them to the system console, forward them to a list of users, or forward them to the logging facility on another host over the network. Each logged message shall include a message header and a message body. The message header shall contain at least a timestamp and a tag string.

If one or more string operands are specified, they shall be logged; otherwise, the message bodies to be logged shall be read from standard input if no -f option is specified, or from the specified file if the -f option is present.

It is implementation-defined whether messages written in locales other than the POSIX locale are effective.

OPTIONS

The logger utility shall conform to XBD 12.2 Utility Syntax Guidelines .

The following options shall be supported:

-f file

Read the log message bodies from file instead of standard input.

-i

Log the process ID of the logger process with each message.

-p priority

Log the message with priority set to priority. The priority is specified as a facility.level pair. The following values for facility shall be supported:

user

Messages generated by arbitrary processes.

local0

Reserved for local use.

local1

Reserved for local use.

local2

Reserved for local use.

local3

Reserved for local use.

local4

Reserved for local use.

local5

Reserved for local use.

local6

Reserved for local use.

local7

Reserved for local use.

The following values for level shall be supported:

emerg

A panic condition.

alert

A condition that should be corrected immediately, such as a corrupted system database.

crit

Critical conditions, such as hard device errors.

err

Errors.

warning

Warning messages.

notice

Conditions that are not error conditions, but that may require special handling.

info

Informational messages.

debug

Messages that contain information normally of use only when debugging a program.

If the -p option is not specified, the priority shall be user.notice.

-t tag

Use the string tag as the tag string in the message header. The default tag is unspecified.

OPERANDS

The following operand shall be supported:

string

One of the string arguments whose contents are concatenated together, in the order specified, separated by single <space> characters.

STDIN

The standard input shall be used if no string operands are specified and either the -f option is not specified or the -f option is specified with a file option-argument of '-' and the implementation treats the '-' as meaning standard input. Otherwise, the standard input shall not be used. See the INPUT FILES section.

Each non-empty line shall be logged as a separate message. It is unspecified whether an empty line is also logged as a separate message.

INPUT FILES

The input files shall be text files.

ENVIRONMENT VARIABLES

The following environment variables shall affect the execution of logger:

LANG

Provide a default value for the internationalization variables that are unset or null. (See XBD 8.2 Internationalization Variables for the precedence of internationalization variables used to determine the values of locale categories.)

LC_ALL

If set to a non-empty string value, override the values of all the other internationalization variables.

LC_CTYPE

Determine the locale for the interpretation of sequences of bytes of text data as characters (for example, single-byte as opposed to multi-byte characters in arguments).

LC_MESSAGES

Determine the locale that should be used to affect the format and contents of diagnostic messages written to standard error. (This means diagnostics from logger to the user or application, not diagnostic messages that the user is sending to the system administrator.)

NLSPATH

^[XSI] Determine the location of messages objects and message catalogs.

ASYNCHRONOUS EVENTS

Default.

STDOUT

Not used.

STDERR

The standard error shall be used only for diagnostic messages.

OUTPUT FILES

Unspecified.

EXTENDED DESCRIPTION

None.

EXIT STATUS

The following exit values shall be returned:

 0

Successful completion.

>0

An error occurred.

CONSEQUENCES OF ERRORS

Default.

APPLICATION USAGE

This utility allows logging of information for later use by a system administrator or programmer in determining why non-interactive utilities have failed. The locations of the saved messages, their format, and retention period are all unspecified. There is no method for a conforming application to read messages, once written.

EXAMPLES

A batch application, running non-interactively, tries to read a configuration file and fails; it may attempt to notify the system administrator with:

logger myname: unable to read file foo. [timestamp]

RATIONALE

The standard developers believed strongly that some method of alerting administrators to errors was necessary. The obvious example is a batch utility, running non-interactively, that is unable to read its configuration files or that is unable to create or write its results file. However, the standard developers did not wish to define the format or delivery mechanisms as they have historically been (and will probably continue to be) very system-specific, as well as involving functionality clearly outside the scope of this volume of POSIX.1-2024.

The text with LC_MESSAGES about diagnostic messages means diagnostics from logger to the user or application, not diagnostic messages that the user is sending to the system administrator.

Multiple string arguments are allowed, similar to echo, for ease-of-use.

Like the utilities mailx and lp, logger is admittedly difficult to test. This was not deemed sufficient justification to exclude these utilities from this volume of POSIX.1-2024. It is also arguable that they are, in fact, testable, but that the tests themselves are not portable.

FUTURE DIRECTIONS

None.

SEE ALSO

lp , mailx , write

XBD 8. Environment Variables

CHANGE HISTORY

First released in Issue 4.

Issue 7

SD5-XCU-ERN-97 is applied, updating the SYNOPSIS.

Issue 8

Austin Group Defect 917 is applied, adding the -f, -i, -p, and -t options, and specifying the behavior when logger is executed with no operands.

Austin Group Defect 1122 is applied, changing the description of NLSPATH .