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Интерактивная система просмотра системных руководств (man-ов)

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mesg (1)
  • mesg (1) ( Solaris man: Команды и прикладные программы пользовательского уровня )
  • mesg (1) ( FreeBSD man: Команды и прикладные программы пользовательского уровня )
  • mesg (1) ( Русские man: Команды и прикладные программы пользовательского уровня )
  • mesg (1) ( Linux man: Команды и прикладные программы пользовательского уровня )
  • >> mesg (1) ( POSIX man: Команды и прикладные программы пользовательского уровня )
  •  

    NAME

    mesg - permit or deny messages
     
    

    SYNOPSIS

    mesg [y|n]  

    DESCRIPTION

    The mesg utility shall control whether other users are allowed to send messages via write, talk, or other utilities to a terminal device. The terminal device affected shall be determined by searching for the first terminal in the sequence of devices associated with standard input, standard output, and standard error, respectively. With no arguments, mesg shall report the current state without changing it. Processes with appropriate privileges may be able to send messages to the terminal independent of the current state.  

    OPTIONS

    None.  

    OPERANDS

    The following operands shall be supported in the POSIX locale:

    y
    Grant permission to other users to send messages to the terminal device.
    n
    Deny permission to other users to send messages to the terminal device.

     

    STDIN

    Not used.  

    INPUT FILES

    None.  

    ENVIRONMENT VARIABLES

    The following environment variables shall affect the execution of mesg:

    LANG
    Provide a default value for the internationalization variables that are unset or null. (See the Base Definitions volume of IEEE Std 1003.1-2001, 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).
    LC_MESSAGES
    Determine the locale that should be used to affect the format and contents of diagnostic messages written (by mesg) to standard error.
    NLSPATH
    Determine the location of message catalogs for the processing of LC_MESSAGES .

     

    ASYNCHRONOUS EVENTS

    Default.  

    STDOUT

    If no operand is specified, mesg shall display the current terminal state in an unspecified format.  

    STDERR

    The standard error shall be used only for diagnostic messages.  

    OUTPUT FILES

    None.  

    EXTENDED DESCRIPTION

    None.  

    EXIT STATUS

    The following exit values shall be returned:

     0
    Receiving messages is allowed.
     1
    Receiving messages is not allowed.
    >1
    An error occurred.

     

    CONSEQUENCES OF ERRORS

    Default.

    The following sections are informative.  

    APPLICATION USAGE

    The mechanism by which the message status of the terminal is changed is unspecified. Therefore, unspecified actions may cause the status of the terminal to change after mesg has successfully completed. These actions may include, but are not limited to: another invocation of the mesg utility, login procedures; invocation of the stty utility, invocation of the chmod utility or chmod() function, and so on.  

    EXAMPLES

    None.  

    RATIONALE

    The terminal changed by mesg is that associated with the standard input, output, or error, rather than the controlling terminal for the session. This is because users logged in more than once should be able to change any of their login terminals without having to stop the job running in those sessions. This is not a security problem involving the terminals of other users because appropriate privileges would be required to affect the terminal of another user.

    The method of checking each of the first three file descriptors in sequence until a terminal is found was adopted from System V.

    The file /dev/tty is not specified for the terminal device because it was thought to be too restrictive. Typical environment changes for the n operand are that write permissions are removed for others and group from the appropriate device. It was decided to leave the actual description of what is done as unspecified because of potential differences between implementations.

    The format for standard output is unspecified because of differences between historical implementations. This output is generally not useful to shell scripts (they can use the exit status), so exact parsing of the output is unnecessary.  

    FUTURE DIRECTIONS

    None.  

    SEE ALSO

    talk , write()  

    COPYRIGHT

    Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 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 .


     

    Index

    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


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