Some of the functionality described in this section shall be
provided on implementations that support the User Portability
Utilities option as described in the text, and is not further
shaded for this option.
The following environment variables shall affect the execution of
mailx:
DEAD Determine the pathname of the file in which to save
partial messages in case of interrupts or delivery
errors. The default shall be dead.letter in the
directory named by the HOME variable. The behavior of
mailx in saving partial messages is unspecified if the
User Portability Utilities option is not supported and
DEAD is not defined with the value /dev/null.
EDITOR Determine the name of a utility to invoke when the edit
(see Commands in mailx) or ~e (see Command Escapes in
mailx) command is used. The default editor is
unspecified. On XSI-conformant systems it is ed. The
effects of this variable are unspecified if the User
Portability Utilities option is not supported.
HOME Determine the pathname of the user's home directory.
LANG Provide a default value for the internationalization
variables that are unset or null. (See the Base
Definitions volume of POSIX.1‐2017, Section 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 and input files) and the
handling of case-insensitive address and header-field
comparisons.
LC_TIME This variable may determine the format and contents of
the date and time strings written by mailx. This
volume of POSIX.1‐2017 specifies the effects of this
variable only for systems supporting the User
Portability Utilities option.
LC_MESSAGES
Determine the locale that should be used to affect the
format and contents of diagnostic messages written to
standard error and informative messages written to
standard output.
LISTER Determine a string representing the command for writing
the contents of the folder directory to standard output
when the folders command is given (see folders in
Commands in mailx). Any string acceptable as a
command_string operand to the sh -c command shall be
valid. If this variable is null or not set, the output
command shall be ls. The effects of this variable are
unspecified if the User Portability Utilities option is
not supported.
MAILRC Determine the pathname of the user start-up file. The
default shall be .mailrc in the directory referred to
by the HOME environment variable. The behavior of mailx
is unspecified if the User Portability Utilities option
is not supported and MAILRC is not defined with the
value /dev/null.
MBOX Determine a pathname of the file to save messages from
the system mailbox that have been read. The exit
command shall override this function, as shall saving
the message explicitly in another file. The default
shall be mbox in the directory named by the HOME
variable. The effects of this variable are unspecified
if the User Portability Utilities option is not
supported.
NLSPATH Determine the location of message catalogs for the
processing of LC_MESSAGES.
PAGER Determine a string representing an output filtering or
pagination command for writing the output to the
terminal. Any string acceptable as a command_string
operand to the sh -c command shall be valid. When
standard output is a terminal device, the message
output shall be piped through the command if the mailx
internal variable crt is set to a value less the number
of lines in the message; see Internal Variables in
mailx. If the PAGER variable is null or not set, the
paginator shall be either more or another paginator
utility documented in the system documentation. The
effects of this variable are unspecified if the User
Portability Utilities option is not supported.
SHELL Determine the name of a preferred command interpreter.
The default shall be sh. The effects of this variable
are unspecified if the User Portability Utilities
option is not supported.
TERM If the internal variable screen is not specified,
determine the name of the terminal type to indicate in
an unspecified manner the number of lines in a
screenful of headers. If TERM is not set or is set to
null, an unspecified default terminal type shall be
used and the value of a screenful is unspecified. The
effects of this variable are unspecified if the User
Portability Utilities option is not supported.
TZ This variable may determine the timezone used to
calculate date and time strings written by mailx. If
TZ is unset or null, an unspecified default timezone
shall be used.
VISUAL Determine a pathname of a utility to invoke when the
visual command (see Commands in mailx) or ~v command-
escape (see Command Escapes in mailx) is used. If this
variable is null or not set, the full-screen editor
shall be vi. The effects of this variable are
unspecified if the User Portability Utilities option is
not supported.
