удаленное выполнение команд (remote command execution)
Пролог (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.
Имя (Name)
uux — remote command execution
Синопсис (Synopsis)
uux [-jnp] command-string
Описание (Description)
The uux utility shall gather zero or more files from various
systems, execute a shell pipeline (see Section 2.9, Shell
Commands) on a specified system, and then send the standard
output of the command to a file on a specified system. Only the
first command of a pipeline can have a system-name! prefix. All
other commands in the pipeline shall be executed on the system of
the first command.
The following restrictions are applicable to the shell pipeline
processed by uux:
* In gathering files from different systems, pathname expansion
shall not be performed by uux. Thus, a request such as:
uux "c99 remsys!~/*.c"
would attempt to copy the file named literally *.c to the
local system.
* The redirection operators ">>", "<<", ">|", and ">&" shall
not be accepted. Any use of these redirection operators shall
cause this utility to write an error message describing the
problem and exit with a non-zero exit status.
* The reserved word ! cannot be used at the head of the
pipeline to modify the exit status. (See the command-string
operand description below.)
* Alias substitution shall not be performed.
A filename can be specified as for uucp; it can be an absolute
pathname, a pathname preceded by ~name (which is replaced by the
corresponding login directory), a pathname specified as ~/dest
(dest is prefixed by the public directory called PUBDIR; the
actual location of PUBDIR is implementation-defined), or a simple
filename (which is prefixed by uux with the current directory).
See uucp(1p) for the details.
The execution of commands on remote systems shall take place in
an execution directory known to the uucp system. All files
required for the execution shall be put into this directory
unless they already reside on that machine. Therefore, the
application shall ensure that non-local filenames (without path
or machine reference) are unique within the uux request.
The uux utility shall attempt to get all files to the execution
system. For files that are output files, the application shall
ensure that the filename is escaped using parentheses.
The remote system shall notify the user by mail if the requested
command on the remote system was disallowed or the files were not
accessible. This notification can be turned off by the -n option.
Typical implementations of this utility require a communications
line configured to use the Base Definitions volume of
POSIX.1‐2017, Chapter 11, General Terminal Interface, but other
communications means may be used. On systems where there are no
available communications means (either temporarily or
permanently), this utility shall write an error message
describing the problem and exit with a non-zero exit status.
The uux utility cannot guarantee support for all character
encodings in all circumstances. For example, transmission data
may be restricted to 7 bits by the underlying network, 8-bit data
and filenames 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 and that only characters defined in the
portable filename character set be used for naming files.
Параметры (Options)
The uux utility shall conform to the Base Definitions volume of
POSIX.1‐2017, Section 12.2, Utility Syntax Guidelines.
The following options shall be supported:
-j Write the job identification string to standard output.
This job identification can be used by uustat to obtain
the status or terminate a job.
-n Do not notify the user if the command fails.
-p Make the standard input to uux the standard input to
the command-string.
Операнды (Operands)
The following operand shall be supported:
command-string
A string made up of one or more arguments that are
similar to normal command arguments, except that the
command and any filenames can be prefixed by system-
name!. A null system-name shall be interpreted as the
local system.
Стандартный ввод (Stdin)
The standard input shall not be used unless the '-' or -p option
is specified; in those cases, the standard input shall be made
the standard input of the command-string.
Входные файлы (Input files)
Input files shall be selected according to the contents of
command-string.
Переменные окружения (Environment variables)
The following environment variables shall affect the execution of
uux:
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).
LC_MESSAGES
Determine the locale that should be used to affect the
format and contents of diagnostic messages written to
standard error.
NLSPATH Determine the location of message catalogs for the
processing of LC_MESSAGES.
Асинхронные события (Asynchronous events)
Default.
Стандартный вывод (Stdout)
The standard output shall not be used unless the -j option is
specified; in that case, the job identification string shall be
written to standard output in the following format:
"%s\n", <jobid>
Стандартный вывод сообщений (Stderr)
The standard error shall be used only for diagnostic messages.
Выходные файлы (Output files)
Output files shall be created or written, or both, according to
the contents of command-string.
If -n is not used, mail files shall be modified following any
command or file-access failures on the remote system.
Расширенное описание (Extended description)
None.
Статус выхода (Exit)
The following exit values shall be returned:
0 Successful completion.
>0 An error occurred.
Последствия ошибок (Consequences of errors)
Default.
The following sections are informative.
Использование в приложениях (Application usage)
This utility is part of the UUCP Utilities option and need not be
supported by all implementations.
Note that, for security reasons, many installations limit the
list of commands executable on behalf of an incoming request from
uux. Many sites permit little more than the receipt of mail via
uux.
Any characters special to the command interpreter should be
quoted either by quoting the entire command-string or quoting the
special characters as individual arguments.
As noted in uucp, shell pattern matching notation characters
appearing in pathnames are expanded on the appropriate local
system. This is done under the control of local settings of
LC_COLLATE and LC_CTYPE. Thus, care should be taken when using
bracketed filename patterns, as collation and typing rules may
vary from one system to another. Also be aware that certain types
of expression (that is, equivalence classes, character classes,
and collating symbols) need not be supported on non-
internationalized systems.
Примеры (Examples)
1. The following command gets file1 from system a and file2 from
system b, executes diff on the local system, and puts the
results in file.diff in the local PUBDIR directory. (PUBDIR
is the uucp public directory on the local system.)
uux "!diff a!/usr/file1 b!/a4/file2 >!~/file.diff"
2. The following command fails because uux places all files
copied to a system in the same working directory. Although
the files xyz are from two different systems, their filenames
are the same and conflict.
uux "!diff a!/usr1/xyz b!/usr2/xyz >!~/xyz.diff"
3. The following command succeeds (assuming diff is permitted on
system a) because the file local to system a is not copied to
the working directory, and hence does not conflict with the
file from system c.
uux "a!diff a!/usr/xyz c!/usr/xyz >!~/xyz.diff"
Обоснование (Rationale)
None.
Будущие направления (Future directions)
None.
Смотри также (See also)
Chapter 2, Shell Command Language, uucp(1p), uuencode(1p),
uustat(1p)
The Base Definitions volume of POSIX.1‐2017, Chapter 8,
Environment Variables, Chapter 11, General Terminal Interface,
Section 12.2, Utility Syntax Guidelines
