logger - log messages
The logger utility saves a message, in an unspecified manner and format, containing the string operands provided by the user. The messages are expected to be evaluated later by personnel performing system administration tasks.
It is implementation-defined whether messages written in locales other than the POSIX locale are effective.
The following operand shall be supported:
- One of the string arguments whose contents are concatenated together, in the order specified, separated by single <space> characters.
The following environment variables shall affect the execution of logger:
- Provide a default value for the internationalization variables that are unset or null. (See XBD Internationalization Variables for the precedence of internationalization variables used to determine the values of locale categories.)
- If set to a non-empty string value, override the values of all the other internationalization variables.
- 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).
- 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.)
- [XSI] Determine the location of message catalogs for the processing of LC_MESSAGES.
The standard error shall be used only for diagnostic messages.
The following exit values shall be returned:
- Successful completion.
- An error occurred.
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.
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]
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.1-2017.
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.1-2017. It is also arguable that they are, in fact, testable, but that the tests themselves are not portable.
lp, mailx, write
XBD Environment Variables
First released in Issue 4.
SD5-XCU-ERN-97 is applied, updating the SYNOPSIS.
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