mailx

MAILX(1POSIX)               POSIX Programmer's Manual              MAILX(1POSIX)



PROLOG
       This manual page is part of the POSIX Programmer's Manual.  The Linux
       implementation of this interface may differ (consult the corresponding
       Linux manual page for details of Linux behavior), or the interface may
       not be implemented on Linux.


NAME
       mailx — process messages

SYNOPSIS
   Send Mode
           mailx [−s subject] address...

   Receive Mode
           mailx −e

           mailx [−HiNn] [−F] [−u user]

           mailx −f [−HiNn] [−F] [file]

DESCRIPTION
       The mailx utility provides a message sending and receiving facility. It
       has two major modes, selected by the options used: Send Mode and Receive
       Mode.

       On systems that do not support the User Portability Utilities option, an
       application using mailx shall have the ability to send messages in an
       unspecified manner (Send Mode). Unless the first character of one or more
       lines is <tilde> ('~'), all characters in the input message shall appear
       in the delivered message, but additional characters may be inserted in
       the message before it is retrieved.

       On systems supporting the User Portability Utilities option, mail-
       receiving capabilities and other interactive features, Receive Mode,
       described below, also shall be enabled.

   Send Mode
       Send Mode can be used by applications or users to send messages from the
       text in standard input.

   Receive Mode
       Receive Mode is more oriented towards interactive users. Mail can be read
       and sent in this interactive mode.

       When reading mail, mailx provides commands to facilitate saving,
       deleting, and responding to messages. When sending mail, mailx allows
       editing, reviewing, and other modification of the message as it is
       entered.

       Incoming mail shall be stored in one or more unspecified locations for
       each user, collectively called the system mailbox for that user. When
       mailx is invoked in Receive Mode, the system mailbox shall be the default
       place to find new mail. As messages are read, they shall be marked to be
       moved to a secondary file for storage, unless specific action is taken.
       This secondary file is called the mbox and is normally located in the
       directory referred to by the HOME environment variable (see MBOX in the
       ENVIRONMENT VARIABLES section for a description of this file).  Messages
       shall remain in this file until explicitly removed. When the −f option is
       used to read mail messages from secondary files, messages shall be
       retained in those files unless specifically removed. All three of these
       locations—system mailbox, mbox, and secondary file—are referred to in
       this section as simply ``mailboxes'', unless more specific identification
       is required.

OPTIONS
       The mailx utility shall conform to the Base Definitions volume of
       POSIX.1‐2008, Section 12.2, Utility Syntax Guidelines.

       The following options shall be supported. (Only the −s subject option
       shall be required on all systems. The other options are required only on
       systems supporting the User Portability Utilities option.)

       −e        Test for the presence of mail in the system mailbox. The mailx
                 utility shall write nothing and exit with a successful return
                 code if there is mail to read.

       −f        Read messages from the file named by the file operand instead
                 of the system mailbox. (See also folder.)  If no file operand
                 is specified, read messages from mbox instead of the system
                 mailbox.

       −F        Record the message in a file named after the first recipient.
                 The name is the login-name portion of the address found first
                 on the To: line in the mail header. Overrides the record
                 variable, if set (see Internal Variables in mailx).

       −H        Write a header summary only.

       −i        Ignore interrupts. (See also ignore.)

       −n        Do not initialize from the system default start-up file. See
                 the EXTENDED DESCRIPTION section.

       −N        Do not write an initial header summary.

       −s subject
                 Set the Subject header field to subject.  All characters in the
                 subject string shall appear in the delivered message. The
                 results are unspecified if subject is longer than {LINE_MAX} −
                 10 bytes or contains a <newline>.

       −u user   Read the system mailbox of the login name user.  This shall
                 only be successful if the invoking user has appropriate
                 privileges to read the system mailbox of that user.

OPERANDS
       The following operands shall be supported:

       address   Addressee of message. When −n is specified and no user start-up
                 files are accessed (see the EXTENDED DESCRIPTION section), the
                 user or application shall ensure this is an address to pass to
                 the mail delivery system. Any system or user start-up files may
                 enable aliases (see alias under Commands in mailx) that may
                 modify the form of address before it is passed to the mail
                 delivery system.

       file      A pathname of a file to be read instead of the system mailbox
                 when −f is specified. The meaning of the file option-argument
                 shall be affected by the contents of the folder internal
                 variable; see Internal Variables in mailx.

STDIN
       When mailx is invoked in Send Mode (the first synopsis line), standard
       input shall be the message to be delivered to the specified addresses.
       When in Receive Mode, user commands shall be accepted from stdin.  If the
       User Portability Utilities option is not supported, standard input lines
       beginning with a <tilde> ('~') character produce unspecified results.

       If the User Portability Utilities option is supported, then in both Send
       and Receive Modes, standard input lines beginning with the escape
       character (usually <tilde> ('~')) shall affect processing as described in
       Command Escapes in mailx.

INPUT FILES
       When mailx is used as described by this volume of POSIX.1‐2008, the file
       option-argument (see the −f option) and the mbox shall be text files
       containing mail messages, formatted as described in the OUTPUT FILES
       section. The nature of the system mailbox is unspecified; it need not be
       a file.

ENVIRONMENT VARIABLES
       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.1‐2008, 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.1‐2008
                 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 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.

ASYNCHRONOUS EVENTS
       When mailx is in Send Mode and standard input is not a terminal, it shall
       take the standard action for all signals.

       In Receive Mode, or in Send Mode when standard input is a terminal, if a
       SIGINT signal is received:

        1. If in command mode, the current command, if there is one, shall be
           aborted, and a command-mode prompt shall be written.

        2. If in input mode:

            a. If ignore is set, mailx shall write "@\n", discard the current
               input line, and continue processing, bypassing the message-abort
               mechanism described in item 2b.

            b. If the interrupt was received while sending mail, either when in
               Receive Mode or in Send Mode, a message shall be written, and
               another subsequent interrupt, with no other intervening
               characters typed, shall be required to abort the mail message.
               If in Receive Mode and another interrupt is received, a command-
               mode prompt shall be written.  If in Send Mode and another
               interrupt is received, mailx shall terminate with a non-zero
               status.

               In both cases listed in item b, if the message is not empty:

                i.  If save is enabled and the file named by DEAD can be
                    created, the message shall be written to the file named by
                    DEAD.  If the file exists, the message shall be written to
                    replace the contents of the file.

               ii.  If save is not enabled, or the file named by DEAD cannot be
                    created, the message shall not be saved.

       The mailx utility shall take the standard action for all other signals.

STDOUT
       In command and input modes, all output, including prompts and messages,
       shall be written to standard output.

STDERR
       The standard error shall be used only for diagnostic messages.

OUTPUT FILES
       Various mailx commands and command escapes can create or add to files,
       including the mbox, the dead-letter file, and secondary mailboxes. When
       mailx is used as described in this volume of POSIX.1‐2008, these files
       shall be text files, formatted as follows:

              line beginning with From<space>
              [one or more header-lines; see Commands in mailx]
              empty line
              [zero or more body lines
              empty line]
              [line beginning with From<space>...]

       where each message begins with the From <space> line shown, preceded by
       the beginning of the file or an empty line.  (The From <space> line is
       considered to be part of the message header, but not one of the header-
       lines referred to in Commands in mailx; thus, it shall not be affected by
       the discard, ignore, or retain commands.) The formats of the remainder of
       the From <space> line and any additional header lines are unspecified,
       except that none shall be empty. The format of a message body line is
       also unspecified, except that no line following an empty line shall start
       with From <space>; mailx shall modify any such user-entered message body
       lines (following an empty line and beginning with From <space>) by adding
       one or more characters to precede the 'F'; it may add these characters to
       From <space> lines that are not preceded by an empty line.

       When a message from the system mailbox or entered by the user is not a
       text file, it is implementation-defined how such a message is stored in
       files written by mailx.

EXTENDED DESCRIPTION
       The functionality in the entire EXTENDED DESCRIPTION section shall be
       provided on implementations supporting the User Portability Utilities
       option.  The functionality described in this section shall be provided on
       implementations that support the User Portability Utilities option (and
       the rest of this section is not further shaded for this option).

       The mailx utility need not support for all character encodings in all
       circumstances. For example, inter-system mail may be restricted to 7-bit
       data by the underlying network, 8-bit data need not be portable to non-
       internationalized systems, and so on. Under these circumstances, it is
       recommended that only characters defined in the ISO/IEC 646:1991 standard
       International Reference Version (equivalent to ASCII) 7-bit range of
       characters be used.

       When mailx is invoked using one of the Receive Mode synopsis forms, it
       shall write a page of header-summary lines (if −N was not specified and
       there are messages, see below), followed by a prompt indicating that
       mailx can accept regular commands (see Commands in mailx); this is termed
       command mode.  The page of header-summary lines shall contain the first
       new message if there are new messages, or the first unread message if
       there are unread messages, or the first message. When mailx is invoked
       using the Send Mode synopsis and standard input is a terminal, if no
       subject is specified on the command line and the asksub variable is set,
       a prompt for the subject shall be written. At this point, mailx shall be
       in input mode. This input mode shall also be entered when using one of
       the Receive Mode synopsis forms and a reply or new message is composed
       using the reply, Reply, followup, Followup, or mail commands and standard
       input is a terminal. When the message is typed and the end of the message
       is encountered, the message shall be passed to the mail delivery
       software. Commands can be entered by beginning a line with the escape
       character (by default, <tilde> ('~')) followed by a single command letter
       and optional arguments. See Commands in mailx for a summary of these
       commands. It is unspecified what effect these commands will have if
       standard input is not a terminal when a message is entered using either
       the Send Mode synopsis, or the Read Mode commands reply, Reply, followup,
       Followup, or mail.

       Note:     For notational convenience, this section uses the default
                 escape character, <tilde>, in all references and examples.

       At any time, the behavior of mailx shall be governed by a set of
       environmental and internal variables.  These are flags and valued
       parameters that can be set and cleared via the mailx set and unset
       commands.

       Regular commands are of the form:

           [command] [msglist] [argument ...]

       If no command is specified in command mode, next shall be assumed. In
       input mode, commands shall be recognized by the escape character, and
       lines not treated as commands shall be taken as input for the message.

       In command mode, each message shall be assigned a sequential number,
       starting with 1.

       All messages have a state that shall affect how they are displayed in the
       header summary and how they are retained or deleted upon termination of
       mailx.  There is at any time the notion of a current message, which shall
       be marked by a '>' at the beginning of a line in the header summary. When
       mailx is invoked using one of the Receive Mode synopsis forms, the
       current message shall be the first new message, if there is a new
       message, or the first unread message if there is an unread message, or
       the first message if there are any messages, or unspecified if there are
       no messages in the mailbox. Each command that takes an optional list of
       messages (msglist) or an optional single message (message) on which to
       operate shall leave the current message set to the highest-numbered
       message of the messages specified, unless the command deletes messages,
       in which case the current message shall be set to the first undeleted
       message (that is, a message not in the deleted state) after the highest-
       numbered message deleted by the command, if one exists, or the first
       undeleted message before the highest-numbered message deleted by the
       command, if one exists, or to an unspecified value if there are no
       remaining undeleted messages. All messages shall be in one of the
       following states:

       new       The message is present in the system mailbox and has not been
                 viewed by the user or moved to any other state. Messages in
                 state new when mailx quits shall be retained in the system
                 mailbox.

       unread    The message has been present in the system mailbox for more
                 than one invocation of mailx and has not been viewed by the
                 user or moved to any other state.  Messages in state unread
                 when mailx quits shall be retained in the system mailbox.

       read      The message has been processed by one of the following
                 commands: ~f, ~m, ~F, ~M, copy, mbox, next, pipe, print, Print,
                 top, type, Type, undelete.  The delete, dp, and dt commands may
                 also cause the next message to be marked as read, depending on
                 the value of the autoprint variable. Messages that are in the
                 system mailbox and in state read when mailx quits shall be
                 saved in the mbox, unless the internal variable hold was set.
                 Messages that are in the mbox or in a secondary mailbox and in
                 state read when mailx quits shall be retained in their current
                 location.

       deleted   The message has been processed by one of the following
                 commands: delete, dp, dt.  Messages in state deleted when mailx
                 quits shall be deleted. Deleted messages shall be ignored until
                 mailx quits or changes mailboxes or they are specified to the
                 undelete command; for example, the message specification
                 /string shall only search the subject lines of messages that
                 have not yet been deleted, unless the command operating on the
                 list of messages is undelete.  No deleted message or deleted
                 message header shall be displayed by any mailx command other
                 than undelete.

       preserved The message has been processed by a preserve command. When
                 mailx quits, the message shall be retained in its current
                 location.

       saved     The message has been processed by one of the following
                 commands: save or write.  If the current mailbox is the system
                 mailbox, and the internal variable keepsave is set, messages in
                 the state saved shall be saved to the file designated by the
                 MBOX variable (see the ENVIRONMENT VARIABLES section). If the
                 current mailbox is the system mailbox, messages in the state
                 saved shall be deleted from the current mailbox, when the quit
                 or file command is used to exit the current mailbox.

       The header-summary line for each message shall indicate the state of the
       message.

       Many commands take an optional list of messages (msglist) on which to
       operate, which defaults to the current message. A msglist is a list of
       message specifications separated by <blank> characters, which can
       include:

       n       Message number n.

       +       The next undeleted message, or the next deleted message for the
               undelete command.

       −       The next previous undeleted message, or the next previous deleted
               message for the undelete command.

       .       The current message.

       ^       The first undeleted message, or the first deleted message for the
               undelete command.

       $       The last message.

       *       All messages.

       n‐m     An inclusive range of message numbers.

       address All messages from address; any address as shown in a header
               summary shall be matchable in this form.

       /string All messages with string in the subject line (case ignored).

       :c      All messages of type c, where c shall be one of:

               d     Deleted messages.

               n     New messages.

               o     Old messages (any not in state read or new).

               r     Read messages.

               u     Unread messages.

       Other commands take an optional message (message) on which to operate,
       which defaults to the current message. All of the forms allowed for
       msglist are also allowed for message, but if more than one message is
       specified, only the first shall be operated on.

       Other arguments are usually arbitrary strings whose usage depends on the
       command involved.

   Start-Up in mailx
       At start-up time, mailx shall take the following steps in sequence:

        1. Establish all variables at their stated default values.

        2. Process command line options, overriding corresponding default
           values.

        3. Import any of the DEAD, EDITOR, MBOX, LISTER, PAGER, SHELL, or VISUAL
           variables that are present in the environment, overriding the
           corresponding default values.

        4. Read mailx commands from an unspecified system start-up file, unless
           the −n option is given, to initialize any internal mailx variables
           and aliases.

        5. Process the start-up file of mailx commands named in the user MAILRC
           variable.

       Most regular mailx commands are valid inside start-up files, the most
       common use being to set up initial display options and alias lists. The
       following commands shall be invalid in the start-up file: !, edit, hold,
       mail, preserve, reply, Reply, shell, visual, Copy, followup, and
       Followup.  Any errors in the start-up file shall either cause mailx to
       terminate with a diagnostic message and a non-zero status or to continue
       after writing a diagnostic message, ignoring the remainder of the lines
       in the start-up file.

       A blank line in a start-up file shall be ignored.

   Internal Variables in mailx
       The following variables are internal mailx variables. Each internal
       variable can be set via the mailx set command at any time. The unset and
       set no name commands can be used to erase variables.

       In the following list, variables shown as:

           variable

       represent Boolean values. Variables shown as:

           variable=value

       shall be assigned string or numeric values. For string values, the rules
       in Commands in mailx concerning filenames and quoting shall also apply.

       The defaults specified here may be changed by the unspecified system
       start-up file unless the user specifies the −n option.

       allnet    All network names whose login name components match shall be
                 treated as identical. This shall cause the msglist message
                 specifications to behave similarly. The default shall be
                 noallnet.  See also the alternates command and the metoo
                 variable.

       append    Append messages to the end of the mbox file upon termination
                 instead of placing them at the beginning. The default shall be
                 noappend.  This variable shall not affect the save command when
                 saving to mbox.

       ask, asksub
                 Prompt for a subject line on outgoing mail if one is not
                 specified on the command line with the −s option. The ask and
                 asksub forms are synonyms; the system shall refer to asksub and
                 noasksub in its messages, but shall accept ask and noask as
                 user input to mean asksub and noasksub.  It shall not be
                 possible to set both ask and noasksub, or noask and asksub.
                 The default shall be asksub, but no prompting shall be done if
                 standard input is not a terminal.

       askbcc    Prompt for the blind copy list. The default shall be noaskbcc.

       askcc     Prompt for the copy list. The default shall be noaskcc.

       autoprint Enable automatic writing of messages after delete and undelete
                 commands. The default shall be noautoprint.

       bang      Enable the special-case treatment of <exclamation-mark>
                 characters ('!')  in escape command lines; see the escape
                 command and Command Escapes in mailx.  The default shall be
                 nobang, disabling the expansion of '!'  in the command argument
                 to the ~!  command and the ~<!command escape.

       cmd=command
                 Set the default command to be invoked by the pipe command. The
                 default shall be nocmd.

       crt=number
                 Pipe messages having more than number lines through the command
                 specified by the value of the PAGER variable. The default shall
                 be nocrt.  If it is set to null, the value used is
                 implementation-defined.

       debug     Enable verbose diagnostics for debugging. Messages are not
                 delivered.  The default shall be nodebug.

       dot       When dot is set, a <period> on a line by itself during message
                 input from a terminal shall also signify end-of-file (in
                 addition to normal end-of-file). The default shall be nodot.
                 If ignoreeof is set (see below), a setting of nodot shall be
                 ignored and the <period> is the only method to terminate input
                 mode.

       escape=c  Set the command escape character to be the character 'c'.  By
                 default, the command escape character shall be <tilde>.  If
                 escape is unset, <tilde> shall be used; if it is set to null,
                 command escaping shall be disabled.

       flipr     Reverse the meanings of the R and r commands. The default shall
                 be noflipr.

       folder=directory
                 The default directory for saving mail files. User-specified
                 filenames beginning with a <plus-sign> ('+') shall be expanded
                 by preceding the filename with this directory name to obtain
                 the real pathname. If directory does not start with a <slash>
                 ('/'), the contents of HOME shall be prefixed to it. The
                 default shall be nofolder.  If folder is unset or set to null,
                 user-specified filenames beginning with '+' shall refer to
                 files in the current directory that begin with the literal '+'
                 character. See also outfolder below. The folder value need not
                 affect the processing of the files named in MBOX and DEAD.

       header    Enable writing of the header summary when entering mailx in
                 Receive Mode. The default shall be header.

       hold      Preserve all messages that are read in the system mailbox
                 instead of putting them in the mbox save file. The default
                 shall be nohold.

       ignore    Ignore interrupts while entering messages. The default shall be
                 noignore.

       ignoreeof Ignore normal end-of-file during message input. Input can be
                 terminated only by entering a <period> ('.')  on a line by
                 itself or by the ~.  command escape. The default shall be
                 noignoreeof.  See also dot above.

       indentprefix=string
                 A string that shall be added as a prefix to each line that is
                 inserted into the message by the ~m command escape. This
                 variable shall default to one <tab>.

       keep      When a system mailbox, secondary mailbox, or mbox is empty,
                 truncate it to zero length instead of removing it. The default
                 shall be nokeep.

       keepsave  Keep the messages that have been saved from the system mailbox
                 into other files in the file designated by the variable MBOX,
                 instead of deleting them. The default shall be nokeepsave.

       metoo     Suppress the deletion of the login name of the user from the
                 recipient list when replying to a message or sending to a
                 group. The default shall be nometoo.

       onehop    When responding to a message that was originally sent to
                 several recipients, the other recipient addresses are normally
                 forced to be relative to the originating author's machine for
                 the response. This flag disables alteration of the recipients'
                 addresses, improving efficiency in a network where all machines
                 can send directly to all other machines (that is, one hop
                 away). The default shall be noonehop.

       outfolder Cause the files used to record outgoing messages to be located
                 in the directory specified by the folder variable unless the
                 pathname is absolute. The default shall be nooutfolder.  See
                 the record variable.

       page      Insert a <form-feed> after each message sent through the pipe
                 created by the pipe command. The default shall be nopage.

       prompt=string
                 Set the command-mode prompt to string.  If string is null or if
                 noprompt is set, no prompting shall occur. The default shall be
                 to prompt with the string "? ".

       quiet     Refrain from writing the opening message and version when
                 entering mailx.  The default shall be noquiet.

       record=file
                 Record all outgoing mail in the file with the pathname file.
                 The default shall be norecord.  See also outfolder above.

       save      Enable saving of messages in the dead-letter file on interrupt
                 or delivery error. See the variable DEAD for the location of
                 the dead-letter file. The default shall be save.

       screen=number
                 Set the number of lines in a screenful of headers for the
                 headers and z commands. If screen is not specified, a value
                 based on the terminal type identified by the TERM environment
                 variable, the window size, the baud rate, or some combination
                 of these shall be used.

       sendwait  Wait for the background mailer to finish before returning. The
                 default shall be nosendwait.

       showto    When the sender of the message was the user who is invoking
                 mailx, write the information from the To: line instead of the
                 From: line in the header summary. The default shall be
                 noshowto.

       sign=string
                 Set the variable inserted into the text of a message when the
                 ~a command escape is given. The default shall be nosign.  The
                 character sequences '\t' and '\n' shall be recognized in the
                 variable as <tab> and <newline> characters, respectively. (See
                 also ~i in Command Escapes in mailx.)

       Sign=string
                 Set the variable inserted into the text of a message when the
                 ~A command escape is given. The default shall be noSign.  The
                 character sequences '\t' and '\n' shall be recognized in the
                 variable as <tab> and <newline> characters, respectively.

       toplines=number
                 Set the number of lines of the message to write with the top
                 command. The default shall be 5.

   Commands in mailx
       The following mailx commands shall be provided. In the following list,
       header refers to lines from the message header, as shown in the OUTPUT
       FILES section.  Header-line refers to lines within the header that begin
       with one or more non-white-space characters, immediately followed by a
       <colon> and white space and continuing until the next line beginning with
       a non-white-space character or an empty line. Header-field refers to the
       portion of a header line prior to the first <colon> in that line.

       For each of the commands listed below, the command can be entered as the
       abbreviation (those characters in the Synopsis command word preceding the
       '['), the full command (all characters shown for the command word,
       omitting the '[' and ']'), or any truncation of the full command down to
       the abbreviation. For example, the exit command (shown as ex[it] in the
       Synopsis) can be entered as ex, exi, or exit.

       The arguments to commands can be quoted, using the following methods:

        *  An argument can be enclosed between paired double-quotes ("") or
           single-quotes (''); any white space, shell word expansion, or
           <backslash> characters within the quotes shall be treated literally
           as part of the argument. A double-quote shall be treated literally
           within single-quotes and vice versa. These special properties of the
           <quotation-mark> characters shall occur only when they are paired at
           the beginning and end of the argument.

        *  A <backslash> outside of the enclosing quotes shall be discarded and
           the following character treated literally as part of the argument.

        *  An unquoted <backslash> at the end of a command line shall be
           discarded and the next line shall continue the command.

       Filenames, where expected, shall be subjected to the following
       transformations, in sequence:

        *  If the filename begins with an unquoted <plus-sign>, and the folder
           variable is defined (see the folder variable), the <plus-sign> shall
           be replaced by the value of the folder variable followed by a
           <slash>.  If the folder variable is unset or is set to null, the
           filename shall be unchanged.

        *  Shell word expansions shall be applied to the filename (see Section
           2.6, Word Expansions).  If more than a single pathname results from
           this expansion and the command is expecting one file, the effects are
           unspecified.

   Declare Aliases
       Synopsis:
                     a[lias] [alias [address...]]
                     g[roup] [alias [address...]]

       Add the given addresses to the alias specified by alias.  The names shall
       be substituted when alias is used as a recipient address specified by the
       user in an outgoing message (that is, other recipients addressed
       indirectly through the reply command shall not be substituted in this
       manner). Mail address alias substitution shall apply only when the alias
       string is used as a full address; for example, when hlj is an alias,
       hlj@posix.com does not trigger the alias substitution. If no arguments
       are given, write a listing of the current aliases to standard output. If
       only an alias argument is given, write a listing of the specified alias
       to standard output. These listings need not reflect the same order of
       addresses that were entered.

   Declare Alternatives
       Synopsis:
                     alt[ernates] name...

       (See also the metoo variable.) Declare a list of alternative names for
       the user's login.  When responding to a message, these names shall be
       removed from the list of recipients for the response. The comparison of
       names shall be in a case-insensitive manner. With no arguments,
       alternates shall write the current list of alternative names.

   Change Current Directory
       Synopsis:
                     cd [directory]
                     ch[dir] [directory]

       Change directory. If directory is not specified, the contents of HOME
       shall be used.

   Copy Messages
       Synopsis:
                     c[opy] [file]
                     c[opy] [msglist] file
                     C[opy] [msglist]

       Copy messages to the file named by the pathname file without marking the
       messages as saved. Otherwise, it shall be equivalent to the save command.

       In the capitalized form, save the specified messages in a file whose name
       is derived from the author of the message to be saved, without marking
       the messages as saved. Otherwise, it shall be equivalent to the Save
       command.

   Delete Messages
       Synopsis:
                     d[elete] [msglist]

       Mark messages for deletion from the mailbox. The deletions shall not
       occur until mailx quits (see the quit command) or changes mailboxes (see
       the folder command). If autoprint is set and there are messages remaining
       after the delete command, the current message shall be written as
       described for the print command (see the print command); otherwise, the
       mailx prompt shall be written.

   Discard Header Fields
       Synopsis:
                     di[scard] [header-field...]
                     ig[nore] [header-field...]

       Suppress the specified header fields when writing messages. Specified
       header-fields shall be added to the list of suppressed header fields.
       Examples of header fields to ignore are status and cc.  The fields shall
       be included when the message is saved. The Print and Type commands shall
       override this command. The comparison of header fields shall be in a
       case-insensitive manner. If no arguments are specified, write a list of
       the currently suppressed header fields to standard output; the listing
       need not reflect the same order of header fields that were entered.

       If both retain and discard commands are given, discard commands shall be
       ignored.

   Delete Messages and Display
       Synopsis:
                     dp [msglist]
                     dt [msglist]

       Delete the specified messages as described for the delete command, except
       that the autoprint variable shall have no effect, and the current message
       shall be written only if it was set to a message after the last message
       deleted by the command. Otherwise, an informational message to the effect
       that there are no further messages in the mailbox shall be written,
       followed by the mailx prompt.

   Echo a String
       Synopsis:
                     ec[ho] string ...

       Echo the given strings, equivalent to the shell echo utility.

   Edit Messages
       Synopsis:
                     e[dit] [msglist]

       Edit the given messages. The messages shall be placed in a temporary file
       and the utility named by the EDITOR variable is invoked to edit each file
       in sequence. The default EDITOR is unspecified.

       The edit command does not modify the contents of those messages in the
       mailbox.

   Exit
       Synopsis:
                     ex[it]
                     x[it]

       Exit from mailx without changing the mailbox. No messages shall be saved
       in the mbox (see also quit).

   Change Folder
       Synopsis:
                     fi[le] [file]
                     fold[er] [file]

       Quit (see the quit command) from the current file of messages and read in
       the file named by the pathname file.  If no argument is given, the name
       and status of the current mailbox shall be written.

       Several unquoted special characters shall be recognized when used as file
       names, with the following substitutions:

       %       The system mailbox for the invoking user.

       %user   The system mailbox for user.

       #       The previous file.

       &       The current mbox.

       +file   The named file in the folder directory. (See the folder
               variable.)

       The default file shall be the current mailbox.

   Display List of Folders
       Synopsis:
                     folders

       Write the names of the files in the directory set by the folder variable.
       The command specified by the LISTER environment variable shall be used
       (see the ENVIRONMENT VARIABLES section).

   Follow Up Specified Messages
       Synopsis:
                     fo[llowup] [message]
                     F[ollowup] [msglist]

       In the lowercase form, respond to a message, recording the response in a
       file whose name is derived from the author of the message. See also the
       save and copy commands and outfolder.

       In the capitalized form, respond to the first message in the msglist,
       sending the message to the author of each message in the msglist.  The
       subject line shall be taken from the first message and the response shall
       be recorded in a file whose name is derived from the author of the first
       message. See also the Save and Copy commands and outfolder.

       Both forms shall override the record variable, if set.

   Display Header Summary for Specified Messages
       Synopsis:
                     f[rom] [msglist]

       Write the header summary for the specified messages.

   Display Header Summary
       Synopsis:
                     h[eaders] [message]

       Write the page of headers that includes the message specified. If the
       message argument is not specified, the current message shall not change.
       However, if the message argument is specified, the current message shall
       become the message that appears at the top of the page of headers that
       includes the message specified. The screen variable sets the number of
       headers per page. See also the z command.

   Help
       Synopsis:
                     hel[p]
                     ?

       Write a summary of commands.

   Hold Messages
       Synopsis:
                     ho[ld] [msglist]
                     pre[serve] [msglist]

       Mark the messages in msglist to be retained in the mailbox when mailx
       terminates. This shall override any commands that might previously have
       marked the messages to be deleted. During the current invocation of
       mailx, only the delete, dp, or dt commands shall remove the preserve
       marking of a message.

   Execute Commands Conditionally
       Synopsis:
                     i[f] s|r
                     mail-commands
                     el[se]
                     mail-commands
                     en[dif]

       Execute commands conditionally, where if s executes the following mail-
       commands, up to an else or endif, if the program is in Send Mode, and
       if r shall cause the mail-commands to be executed only in Receive Mode.

   List Available Commands
       Synopsis:
                     l[ist]

       Write a list of all commands available. No explanation shall be given.

   Mail a Message
       Synopsis:
                     m[ail] address...

       Mail a message to the specified addresses or aliases.

   Direct Messages to mbox
       Synopsis:
                     mb[ox] [msglist]

       Arrange for the given messages to end up in the mbox save file when mailx
       terminates normally. See MBOX.  See also the exit and quit commands.

   Process Next Specified Message
       Synopsis:
                     n[ext] [message]

       If the current message has not been written (for example, by the print
       command) since mailx started or since any other message was the current
       message, behave as if the print command was entered. Otherwise, if there
       is an undeleted message after the current message, make it the current
       message and behave as if the print command was entered. Otherwise, an
       informational message to the effect that there are no further messages in
       the mailbox shall be written, followed by the mailx prompt. Should the
       current message location be the result of an immediately preceding hold,
       mbox, preserve, or touch command, next will act as if the current message
       has already been written.

   Pipe Message
       Synopsis:
                     pi[pe] [[msglist] command]
                     | [[msglist] command]

       Pipe the messages through the given command by invoking the command
       interpreter specified by SHELL with two arguments: −c and command.  (See
       also sh −c.)  The application shall ensure that the command is given as a
       single argument. Quoting, described previously, can be used to accomplish
       this. If no arguments are given, the current message shall be piped
       through the command specified by the value of the cmd variable. If the
       page variable is set, a <form-feed> shall be inserted after each message.

   Display Message with Headers
       Synopsis:
                     P[rint] [msglist]
                     T[ype] [msglist]

       Write the specified messages, including all header lines, to standard
       output. Override suppression of lines by the discard, ignore, and retain
       commands. If crt is set, the messages longer than the number of lines
       specified by the crt variable shall be paged through the command
       specified by the PAGER environment variable.

   Display Message
       Synopsis:
                     p[rint] [msglist]
                     t[ype] [msglist]

       Write the specified messages to standard output. If crt is set, the
       messages longer than the number of lines specified by the crt variable
       shall be paged through the command specified by the PAGER environment
       variable.

   Quit
       Synopsis:
                     q[uit]
                     end-of-file

       Terminate mailx, storing messages that were read in mbox (if the current
       mailbox is the system mailbox and unless hold is set), deleting messages
       that have been explicitly saved (unless keepsave is set), discarding
       messages that have been deleted, and saving all remaining messages in the
       mailbox.

   Reply to a Message List
       Synopsis:
                     R[eply] [msglist]
                     R[espond] [msglist]

       Mail a reply message to the sender of each message in the msglist.  The
       subject line shall be formed by concatenating Re:<space> (unless it
       already begins with that string) and the subject from the first message.
       If record is set to a filename, the response shall be saved at the end of
       that file.

       See also the flipr variable.

   Reply to a Message
       Synopsis:
                     r[eply] [message]
                     r[espond] [message]

       Mail a reply message to all recipients included in the header of the
       message. The subject line shall be formed by concatenating Re:<space>
       (unless it already begins with that string) and the subject from the
       message. If record is set to a filename, the response shall be saved at
       the end of that file.

       See also the flipr variable.

   Retain Header Fields
       Synopsis:
                     ret[ain] [header-field...]

       Retain the specified header fields when writing messages. This command
       shall override all discard and ignore commands. The comparison of header
       fields shall be in a case-insensitive manner. If no arguments are
       specified, write a list of the currently retained header fields to
       standard output; the listing need not reflect the same order of header
       fields that were entered.

   Save Messages
       Synopsis:
                     s[ave] [file]
                     s[ave] [msglist] file
                     S[ave] [msglist]

       Save the specified messages in the file named by the pathname file, or
       the mbox if the file argument is omitted. The file shall be created if it
       does not exist; otherwise, the messages shall be appended to the file.
       The message shall be put in the state saved, and shall behave as
       specified in the description of the saved state when the current mailbox
       is exited by the quit or file command.

       In the capitalized form, save the specified messages in a file whose name
       is derived from the author of the first message. The name of the file
       shall be taken to be the author's name with all network addressing
       stripped off. See also the Copy, followup, and Followup commands and
       outfolder variable.

   Set Variables
       Synopsis:
                     se[t] [name[=[string]] ...] [name=number ...] [noname ...]

       Define one or more variables called name.  The variable can be given a
       null, string, or numeric value. Quoting and <backslash>-escapes can occur
       anywhere in string, as described previously, as if the string portion of
       the argument were the entire argument. The forms name and name= shall be
       equivalent to name="" for variables that take string values. The set
       command without arguments shall write a list of all defined variables and
       their values. The no name form shall be equivalent to unset name.

   Invoke a Shell
       Synopsis:
                     sh[ell]

       Invoke an interactive command interpreter (see also SHELL).

   Display Message Size
       Synopsis:
                     si[ze] [msglist]

       Write the size in bytes of each of the specified messages.

   Read mailx Commands From a File
       Synopsis:
                     so[urce] file

       Read and execute commands from the file named by the pathname file and
       return to command mode.

   Display Beginning of Messages
       Synopsis:
                     to[p] [msglist]

       Write the top few lines of each of the specified messages. If the
       toplines variable is set, it is taken as the number of lines to write.
       The default shall be 5.

   Touch Messages
       Synopsis:
                     tou[ch] [msglist]

       Touch the specified messages. If any message in msglist is not
       specifically deleted nor saved in a file, it shall be placed in the mbox
       upon normal termination. See exit and quit.

   Delete Aliases
       Synopsis:
                     una[lias] [alias]...

       Delete the specified alias names. If a specified alias does not exist,
       the results are unspecified.

   Undelete Messages
       Synopsis:
                     u[ndelete] [msglist]

       Change the state of the specified messages from deleted to read. If
       autoprint is set, the last message of those restored shall be written. If
       msglist is not specified, the message shall be selected as follows:

        *  If there are any deleted messages that follow the current message,
           the first of these shall be chosen.

        *  Otherwise, the last deleted message that also precedes the current
           message shall be chosen.

   Unset Variables
       Synopsis:
                     uns[et] name...

       Cause the specified variables to be erased.

   Edit Message with Full-Screen Editor
       Synopsis:
                     v[isual] [msglist]

       Edit the given messages with a screen editor. Each message shall be
       placed in a temporary file, and the utility named by the VISUAL variable
       shall be invoked to edit each file in sequence. The default editor shall
       be vi.

       The visual command does not modify the contents of those messages in the
       mailbox.

   Write Messages to a File
       Synopsis:
                     w[rite] [msglist] file

       Write the given messages to the file specified by the pathname file,
       minus the message header. Otherwise, it shall be equivalent to the save
       command.

   Scroll Header Display
       Synopsis:
                     z[+|−]

       Scroll the header display forward (if '+' is specified or if no option is
       specified) or backward (if '−' is specified) one screenful. The number of
       headers written shall be set by the screen variable.

   Invoke Shell Command
       Synopsis:
                     !command

       Invoke the command interpreter specified by SHELL with two arguments: −c
       and command.  (See also sh −c.)  If the bang variable is set, each
       unescaped occurrence of '!'  in command shall be replaced with the
       command executed by the previous !  command or ~!  command escape.

   Null Command
       Synopsis:
                     # comment

       This null command (comment) shall be ignored by mailx.

   Display Current Message Number
       Synopsis:
                     =

       Write the current message number.

   Command Escapes in mailx
       The following commands can be entered only from input mode, by beginning
       a line with the escape character (by default, <tilde> ('~')).  See the
       escape variable description for changing this special character. The
       format for the commands shall be:

           <escape-character><command-char><separator>[<arguments>]

       where the <separator> can be zero or more <blank> characters.

       In the following descriptions, the application shall ensure that the
       argument command (but not mailx-command) is a shell command string. Any
       string acceptable to the command interpreter specified by the SHELL
       variable when it is invoked as SHELL −c command_string shall be valid.
       The command can be presented as multiple arguments (that is, quoting is
       not required).

       Command escapes that are listed with msglist or mailx-command arguments
       are invalid in Send Mode and produce unspecified results.

       ~! command
                 Invoke the command interpreter specified by SHELL with two
                 arguments: −c and command; and then return to input mode. If
                 the bang variable is set, each unescaped occurrence of '!'  in
                 command shall be replaced with the command executed by the
                 previous !  command or ~!  command escape.

       ~.        Simulate end-of-file (terminate message input).

       ~: mailx-command, ~_ mailx-command
                 Perform the command-level request.

       ~?        Write a summary of command escapes.

       ~A        This shall be equivalent to ~i Sign.

       ~a        This shall be equivalent to ~i sign.

       ~b name...
                 Add the names to the blind carbon copy (Bcc) list.

       ~c name...
                 Add the names to the carbon copy (Cc) list.

       ~d        Read in the dead-letter file. See DEAD for a description of
                 this file.

       ~e        Invoke the editor, as specified by the EDITOR environment
                 variable, on the partial message.

       ~f [msglist]
                 Forward the specified messages. The specified messages shall be
                 inserted into the current message without alteration. This
                 command escape also shall insert message headers into the
                 message with field selection affected by the discard, ignore,
                 and retain commands.

       ~F [msglist]
                 This shall be the equivalent of the ~f command escape, except
                 that all headers shall be included in the message, regardless
                 of previous discard, ignore, and retain commands.

       ~h        If standard input is a terminal, prompt for a Subject line and
                 the To, Cc, and Bcc lists. Other implementation-defined headers
                 may also be presented for editing. If the field is written with
                 an initial value, it can be edited as if it had just been
                 typed.

       ~i string Insert the value of the named variable, followed by a
                 <newline>, into the text of the message. If the string is unset
                 or null, the message shall not be changed.

       ~m [msglist]
                 Insert the specified messages into the message, prefixing non-
                 empty lines with the string in the indentprefix variable. This
                 command escape also shall insert message headers into the
                 message, with field selection affected by the discard, ignore,
                 and retain commands.

       ~M [msglist]
                 This shall be the equivalent of the ~m command escape, except
                 that all headers shall be included in the message, regardless
                 of previous discard, ignore, and retain commands.

       ~p        Write the message being entered. If the message is longer than
                 crt lines (see Internal Variables in mailx), the output shall
                 be paginated as described for the PAGER variable.

       ~q        Quit (see the quit command) from input mode by simulating an
                 interrupt. If the body of the message is not empty, the partial
                 message shall be saved in the dead-letter file. See DEAD for a
                 description of this file.

       ~r file, ~< file, ~r !command, ~< !command
                 Read in the file specified by the pathname file.  If the
                 argument begins with an <exclamation-mark> ('!'), the rest of
                 the string shall be taken as an arbitrary system command; the
                 command interpreter specified by SHELL shall be invoked with
                 two arguments: −c and command.  The standard output of command
                 shall be inserted into the message.

       ~s string Set the subject line to string.

       ~t name...
                 Add the given names to the To list.

       ~v        Invoke the full-screen editor, as specified by the VISUAL
                 environment variable, on the partial message.

       ~w file   Write the partial message, without the header, onto the file
                 named by the pathname file.  The file shall be created or the
                 message shall be appended to it if the file exists.

       ~x        Exit as with ~q, except the message shall not be saved in the
                 dead-letter file.

       ~| command
                 Pipe the body of the message through the given command by
                 invoking the command interpreter specified by SHELL with two
                 arguments: −c and command.  If the command returns a successful
                 exit status, the standard output of the command shall replace
                 the message. Otherwise, the message shall remain unchanged. If
                 the command fails, an error message giving the exit status
                 shall be written.

EXIT STATUS
       When the −e option is specified, the following exit values are returned:

        0    Mail was found.

       >0    Mail was not found or an error occurred.

       Otherwise, the following exit values are returned:

        0    Successful completion; note that this status implies that all
             messages were sent, but it gives no assurances that any of them
             were actually delivered.

       >0    An error occurred.

CONSEQUENCES OF ERRORS
       When in input mode (Receive Mode) or Send Mode:

        *  If an error is encountered processing an input line beginning with a
           <tilde> ('~') character, (see Command Escapes in mailx), a diagnostic
           message shall be written to standard error, and the message being
           composed may be modified, but this condition shall not prevent the
           message from being sent.

        *  Other errors shall prevent the sending of the message.

       When in command mode:

        *  Default.

       The following sections are informative.

APPLICATION USAGE
       Delivery of messages to remote systems requires the existence of
       communication paths to such systems. These need not exist.

       Input lines are limited to {LINE_MAX} bytes, but mailers between systems
       may impose more severe line-length restrictions. This volume of
       POSIX.1‐2008 does not place any restrictions on the length of messages
       handled by mailx, and for delivery of local messages the only limitations
       should be the normal problems of available disk space for the target mail
       file. When sending messages to external machines, applications are
       advised to limit messages to less than 100000 bytes because some mail
       gateways impose message-length restrictions.

       The format of the system mailbox is intentionally unspecified. Not all
       systems implement system mailboxes as flat files, particularly with the
       advent of multimedia mail messages. Some system mailboxes may be multiple
       files, others records in a database. The internal format of the messages
       themselves is specified with the historical format from Version 7, but
       only after the messages have been saved in some file other than the
       system mailbox. This was done so that many historical applications
       expecting text-file mailboxes are not broken.

       Some new formats for messages can be expected in the future, probably
       including binary data, bit maps, and various multimedia objects. As
       described here, mailx is not prohibited from handling such messages, but
       it must store them as text files in secondary mailboxes (unless some
       extension, such as a variable or command line option, is used to change
       the stored format).  Its method of doing so is implementation-defined and
       might include translating the data into text file-compatible or readable
       form or omitting certain portions of the message from the stored output.

       The discard and ignore commands are not inverses of the retain command.
       The retain command discards all header-fields except those explicitly
       retained.  The discard command keeps all header-fields except those
       explicitly discarded. If headers exist on the retained header list,
       discard and ignore commands are ignored.

EXAMPLES
       None.

RATIONALE
       The standard developers felt strongly that a method for applications to
       send messages to specific users was necessary. The obvious example is a
       batch utility, running non-interactively, that wishes to communicate
       errors or results to a user. However, the actual format, delivery
       mechanism, and method of reading the message are clearly beyond the scope
       of this volume of POSIX.1‐2008.

       The intent of this command is to provide a simple, portable interface for
       sending messages non-interactively. It merely defines a ``front-end'' to
       the historical mail system. It is suggested that implementations
       explicitly denote the sender and recipient in the body of the delivered
       message. Further specification of formats for either the message envelope
       or the message itself were deliberately not made, as the industry is in
       the midst of changing from the current standards to a more
       internationalized standard and it is probably incorrect, at this time, to
       require either one.

       Implementations are encouraged to conform to the various delivery
       mechanisms described in the CCITT X.400 standards or to the equivalent
       Internet standards, described in Internet Request for Comment (RFC)
       documents RFC 819, RFC 822, RFC 920, RFC 921, and RFC 1123.

       Many historical systems modified each body line that started with From
       by prefixing the 'F' with '>'.  It is unnecessary, but allowed, to do
       that when the string does not follow a blank line because it cannot be
       confused with the next header.

       The edit and visual commands merely edit the specified messages in a
       temporary file. They do not modify the contents of those messages in the
       mailbox; such a capability could be added as an extension, such as by
       using different command names.

       The restriction on a subject line being {LINE_MAX}−10 bytes is based on
       the historical format that consumes 10 bytes for Subject:  and the
       trailing <newline>.  Many historical mailers that a message may encounter
       on other systems are not able to handle lines that long, however.

       Like the utilities logger and lp, mailx admittedly is difficult to test.
       This was not deemed sufficient justification to exclude this utility from
       this volume of POSIX.1‐2008. It is also arguable that it is, in fact,
       testable, but that the tests themselves are not portable.

       When mailx is being used by an application that wishes to receive the
       results as if none of the User Portability Utilities option features were
       supported, the DEAD environment variable must be set to /dev/null.
       Otherwise, it may be subject to the file creations described in mailx
       ASYNCHRONOUS EVENTS. Similarly, if the MAILRC environment variable is not
       set to /dev/null, historical versions of mailx and Mail read
       initialization commands from a file before processing begins.  Since the
       initialization that a user specifies could alter the contents of messages
       an application is trying to send, such applications must set MAILRC to
       /dev/null.

       The description of LC_TIME uses ``may affect'' because many historical
       implementations do not or cannot manipulate the date and time strings in
       the incoming mail headers. Some headers found in incoming mail do not
       have enough information to determine the timezone in which the mail
       originated, and, therefore, mailx cannot convert the date and time
       strings into the internal form that then is parsed by routines like
       strftime() that can take LC_TIME settings into account. Changing all
       these times to a user-specified format is allowed, but not required.

       The paginator selected when PAGER is null or unset is partially
       unspecified to allow the System V historical practice of using pg as the
       default. Bypassing the pagination function, such as by declaring that cat
       is the paginator, would not meet with the intended meaning of this
       description. However, any ``portable user'' would have to set PAGER
       explicitly to get his or her preferred paginator on all systems. The
       paginator choice was made partially unspecified, unlike the VISUAL editor
       choice (mandated to be vi) because most historical pagers follow a common
       theme of user input, whereas editors differ dramatically.

       Options to specify addresses as cc (carbon copy) or bcc (blind carbon
       copy) were considered to be format details and were omitted.

       A zero exit status implies that all messages were sent, but it gives no
       assurances that any of them were actually delivered.  The reliability of
       the delivery mechanism is unspecified and is an appropriate marketing
       distinction between systems.

       In order to conform to the Utility Syntax Guidelines, a solution was
       required to the optional file option-argument to −f.  By making file an
       operand, the guidelines are satisfied and users remain portable.
       However, it does force implementations to support usage such as:

           mailx −fin mymail.box

       The no name method of unsetting variables is not present in all
       historical systems, but it is in System V and provides a logical set of
       commands corresponding to the format of the display of options from the
       mailx set command without arguments.

       The ask and asksub variables are the names selected by BSD and System V,
       respectively, for the same feature. They are synonyms in this volume of
       POSIX.1‐2008.

       The mailx echo command was not documented in the BSD version and has been
       omitted here because it is not obviously useful for interactive users.

       The default prompt on the System V mailx is a <question-mark>, on BSD
       Mail an <ampersand>.  Since this volume of POSIX.1‐2008 chose the mailx
       name, it kept the System V default, assuming that BSD users would not
       have difficulty with this minor incompatibility (that they can override).

       The meanings of r and R are reversed between System V mailx and SunOS
       Mail.  Once again, since this volume of POSIX.1‐2008 chose the mailx
       name, it kept the System V default, but allows the SunOS user to achieve
       the desired results using flipr, an internal variable in System V mailx,
       although it has not been documented in the SVID.

       The indentprefix variable, the retain and unalias commands, and the ~F
       and ~M command escapes were adopted from 4.3 BSD Mail.

       The version command was not included because no sufficiently general
       specification of the version information could be devised that would
       still be useful to a portable user. This command name should be used by
       suppliers who wish to provide version information about the mailx
       command.

       The ``implementation-specific (unspecified) system start-up file''
       historically has been named /etc/mailx.rc, but this specific name and
       location are not required.

       The intent of the wording for the next command is that if any command has
       already displayed the current message it should display a following
       message, but, otherwise, it should display the current message. Consider
       the command sequence:

           next 3
           delete 3
           next

       where the autoprint option was not set. The normative text specifies that
       the second next command should display a message following the third
       message, because even though the current message has not been displayed
       since it was set by the delete command, it has been displayed since the
       current message was anything other than message number 3. This does not
       always match historical practice in some implementations, where the
       command file address followed by next (or the default command) would skip
       the message for which the user had searched.

FUTURE DIRECTIONS
       None.

SEE ALSO
       Chapter 2, Shell Command Language, ed, ls, more, vi

       The Base Definitions volume of POSIX.1‐2008, Chapter 8, Environment
       Variables, Section 12.2, Utility Syntax Guidelines

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
       -- Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electrical
       and Electronics Engineers, Inc and The Open Group.  (This is POSIX.1-2008
       with the 2013 Technical Corrigendum 1 applied.) In the event of any
       discrepancy between this version and the original IEEE and The Open Group
       Standard, the original IEEE and The Open Group Standard is the referee
       document. The original Standard can be obtained online at
       http://www.unix.org/online.html .

       Any typographical or formatting errors that appear in this page are most
       likely to have been introduced during the conversion of the source files
       to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .



IEEE/The Open Group                   2013                         MAILX(1POSIX)