uux: vzdálené provádění příkazů

Originální popis anglicky: uux - remote command execution

Návod, kniha: POSIX Programmer's Manual

STRUČNĚ

uux [-np] command-string uux [-jnp] command-string

POPIS / INSTRUKCE

The uux utility shall gather zero or more files from various systems, execute a shell pipeline (see 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:

 

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 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 IEEE Std 1003.1-2001, 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.

OPTIONS

The uux utility shall conform to the Base Definitions volume of IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guidelines. The following options shall be supported:

-p

Make the standard input to uux the standard input to the command-string.

-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.

 

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.

 

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.

INPUT FILES

Input files shall be selected according to the contents of command-string.

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 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 to standard error.

NLSPATH

Determine the location of message catalogs for the processing of LC_MESSAGES .

 

ASYNCHRONOUS EVENTS

Default.

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:

STDERR

The standard error shall be used only for diagnostic messages.

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.

EXTENDED DESCRIPTION

None.

EXIT STATUS

The following exit values shall be returned:

 0

Successful completion.

>0

An error occurred.

 

CONSEQUENCES OF ERRORS

Default. The following sections are informative.

APPLICATION USAGE

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.

PŘÍKLADY POUŽITÍ

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.)

 

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.

 

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.

 

RATIONALE

None.

FUTURE DIRECTIONS

None.

SOUVISEJÍCÍ

Shell Command Language , uucp , uuencode , uustat

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 .