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



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

NNAAMMEE
       write -- write to another user

SSYYNNOOPPSSIISS
       write _u_s_e_r___n_a_m_e [[_t_e_r_m_i_n_a_l]]

DDEESSCCRRIIPPTTIIOONN
       The _w_r_i_t_e utility shall read lines from the standard input and write
       them to the terminal of the specified user. When first invoked, it
       shall write the message:


           MMeessssaaggee ffrroomm _s_e_n_d_e_r_-_l_o_g_i_n_-_i_d (_s_e_n_d_i_n_g_-_t_e_r_m_i_n_a_l) [[_d_a_t_e]]...

       to _u_s_e_r___n_a_m_e.  When it has successfully completed the connection, the
       sender's terminal shall be alerted twice to indicate that what the
       sender is typing is being written to the recipient's terminal.

       If the recipient wants to reply, this can be accomplished by typing:


           write _s_e_n_d_e_r_-_l_o_g_i_n_-_i_d [[_s_e_n_d_i_n_g_-_t_e_r_m_i_n_a_l]]

       upon receipt of the initial message. Whenever a line of input as
       delimited by an NL, EOF, or EOL special character (see the Base
       Definitions volume of POSIX.1-2017, _C_h_a_p_t_e_r _1_1, _G_e_n_e_r_a_l _T_e_r_m_i_n_a_l
       _I_n_t_e_r_f_a_c_e) is accumulated while in canonical input mode, the
       accumulated data shall be written on the other user's terminal.
       Characters shall be processed as follows:

        *  Typing <alert> shall write the <alert> character to the recipient's
           terminal.

        *  Typing the erase and kill characters shall affect the sender's
           terminal in the manner described by the tteerrmmiiooss interface in the
           Base Definitions volume of POSIX.1-2017, _C_h_a_p_t_e_r _1_1, _G_e_n_e_r_a_l
           _T_e_r_m_i_n_a_l _I_n_t_e_r_f_a_c_e.

        *  Typing the interrupt or end-of-file characters shall cause _w_r_i_t_e to
           write an appropriate message (""EEOOTT\\nn"" in the POSIX locale) to the
           recipient's terminal and exit.

        *  Typing characters from _L_C___C_T_Y_P_E classifications pprriinntt or ssppaaccee
           shall cause those characters to be sent to the recipient's
           terminal.

        *  When and only when the _s_t_t_y iieexxtteenn local mode is enabled, the
           existence and processing of additional special control characters
           and multi-byte or single-byte functions is implementation-defined.

        *  Typing other non-printable characters shall cause implementation-
           defined sequences of printable characters to be written to the
           recipient's terminal.

       To write to a user who is logged in more than once, the _t_e_r_m_i_n_a_l
       argument can be used to indicate which terminal to write to; otherwise,
       the recipient's terminal is selected in an implementation-defined
       manner and an informational message is written to the sender's standard
       output, indicating which terminal was chosen.

       Permission to be a recipient of a _w_r_i_t_e message can be denied or
       granted by use of the _m_e_s_g utility. However, a user's privilege may
       further constrain the domain of accessibility of other users'
       terminals. The _w_r_i_t_e utility shall fail when the user lacks appropriate
       privileges to perform the requested action.

OOPPTTIIOONNSS
       None.

OOPPEERRAANNDDSS
       The following operands shall be supported:

       _u_s_e_r___n_a_m_e Login name of the person to whom the message shall be
                 written. The application shall ensure that this operand is of
                 the form returned by the _w_h_o utility.

       _t_e_r_m_i_n_a_l  Terminal identification in the same format provided by the
                 _w_h_o utility.

SSTTDDIINN
       Lines to be copied to the recipient's terminal are read from standard
       input.

IINNPPUUTT FFIILLEESS
       None.

EENNVVIIRROONNMMEENNTT VVAARRIIAABBLLEESS
       The following environment variables shall affect the execution of
       _w_r_i_t_e:

       _L_A_N_G      Provide a default value for the internationalization
                 variables that are unset or null. (See the Base Definitions
                 volume of POSIX.1-2017, _S_e_c_t_i_o_n _8_._2, _I_n_t_e_r_n_a_t_i_o_n_a_l_i_z_a_t_i_o_n
                 _V_a_r_i_a_b_l_e_s for the precedence of internationalization
                 variables used to determine the values of locale categories.)

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

       _L_C___C_T_Y_P_E  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). If the recipient's locale does not use an _L_C___C_T_Y_P_E
                 equivalent to the sender's, the results are undefined.

       _L_C___M_E_S_S_A_G_E_S
                 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.

       _N_L_S_P_A_T_H   Determine the location of message catalogs for the processing
                 of _L_C___M_E_S_S_A_G_E_S.

AASSYYNNCCHHRROONNOOUUSS EEVVEENNTTSS
       If an interrupt signal is received, _w_r_i_t_e shall write an appropriate
       message on the recipient's terminal and exit with a status of zero. It
       shall take the standard action for all other signals.

SSTTDDOOUUTT
       An informational message shall be written to standard output if a
       recipient is logged in more than once.

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

OOUUTTPPUUTT FFIILLEESS
       The recipient's terminal is used for output.

EEXXTTEENNDDEEDD DDEESSCCRRIIPPTTIIOONN
       None.

EEXXIITT SSTTAATTUUSS
       The following exit values shall be returned:

        0    Successful completion.

       >0    The addressed user is not logged on or the addressed user denies
             permission.

CCOONNSSEEQQUUEENNCCEESS OOFF EERRRROORRSS
       Default.

       _T_h_e _f_o_l_l_o_w_i_n_g _s_e_c_t_i_o_n_s _a_r_e _i_n_f_o_r_m_a_t_i_v_e_.

AAPPPPLLIICCAATTIIOONN UUSSAAGGEE
       The _t_a_l_k utility is considered by some users to be a more usable
       utility on full-screen terminals.

EEXXAAMMPPLLEESS
       None.

RRAATTIIOONNAALLEE
       The _w_r_i_t_e utility was included in this volume of POSIX.1-2017 since it
       can be implemented on all terminal types. The standard developers
       considered the _t_a_l_k utility, which cannot be implemented on certain
       terminals, to be a ``better'' communications interface. Both of these
       programs are in widespread use on historical implementations.
       Therefore, the standard developers decided that both utilities should
       be specified.

       The format of the terminal name is unspecified, but the descriptions of
       _p_s, _t_a_l_k, _w_h_o, and _w_r_i_t_e require that they all use or accept the same
       format.

FFUUTTUURREE DDIIRREECCTTIIOONNSS
       None.

SSEEEE AALLSSOO
       _m_e_s_g, _t_a_l_k, _w_h_o

       The Base Definitions volume of POSIX.1-2017, _C_h_a_p_t_e_r _8, _E_n_v_i_r_o_n_m_e_n_t
       _V_a_r_i_a_b_l_e_s, _C_h_a_p_t_e_r _1_1, _G_e_n_e_r_a_l _T_e_r_m_i_n_a_l _I_n_t_e_r_f_a_c_e

CCOOPPYYRRIIGGHHTT
       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                             WRITE(1)
