|
HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|
|
PROLOG | NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OPERANDS | STDIN | INPUT FILES | ENVIRONMENT VARIABLES | ASYNCHRONOUS EVENTS | STDOUT | STDERR | OUTPUT FILES | EXTENDED DESCRIPTION | EXIT STATUS | CONSEQUENCES OF ERRORS | APPLICATION USAGE | EXAMPLES | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
|
|
|
MAILX(1P) POSIX Programmer's Manual MAILX(1P)
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.
mailx — process messages
Send Mode
mailx [-s subject] address...
Receive Mode
mailx -e
mailx [-HiNn] [-F] [-u user]
mailx -f [-HiNn] [-F] [file]
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.
The mailx utility shall conform to the Base Definitions volume of
POSIX.1‐2017, 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.
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.
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.
When mailx is used as described by this volume of POSIX.1‐2017,
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.
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.
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.
In command and input modes, all output, including prompts and
messages, shall be written to standard output.
The standard error shall be used only for diagnostic messages.
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.1‐2017, 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.
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 user 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 a start-up file:
!, edit, hold, mail, preserve, reply, Reply, shell, visual, Copy,
followup, and Followup. Any errors in a 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 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.
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.
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.
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.1‐2017 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.
None.
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.1‐2017.
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 920, RFC 921, RFC 1123, and
RFC 5322 (which succeeded RFC 822).
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.1‐2017. 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.1‐2017.
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.1‐2017 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.1‐2017 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.
None.
Chapter 2, Shell Command Language, ed(1p), ls(1p), more(1p),
vi(1p)
The Base Definitions volume of POSIX.1‐2017, Chapter 8,
Environment Variables, Section 12.2, Utility Syntax Guidelines
Portions of this text are reprinted and reproduced in electronic
form from IEEE Std 1003.1-2017, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The
Open Group Base Specifications Issue 7, 2018 Edition, Copyright
(C) 2018 by the Institute of Electrical and Electronics Engineers,
Inc and The Open Group. 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.opengroup.org/unix/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 2017 MAILX(1P)
Pages that refer to this page: logger(1p), lp(1p), uucp(1p), uuencode(1p)
|
HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|