The Single UNIX ® Specification, Version 2
Copyright © 1997 The Open Group


uux - remote command execution


uux [-np] command-string

uux [-jnp] command-string

uux [-][-jn] command-string


The uux utility will 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 are executed on the system of the first command.

The following restrictions are applicable to the shell pipeline processed by uux:

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-dependent), 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 takes place in an execution directory known to the uucp system. All files required for the execution will be put into this directory unless they already reside on that machine. Therefore, the non-local filenames (without path or machine reference) must be unique within the uux request.

The uux utility will attempt to get all files to the execution system. For files that are output files, the filename must be escaped using parentheses.

The remote system will 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 XBD specification, 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 will 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-internationalised 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.


The uux utility supports the XBD specification, Utility Syntax Guidelines  , except that - is supported as an option in the obsolescent version, rather than an operand. The following options are supported:
Make the standard input to uux the standard input to the command-string.
Write the job identification string to standard output. This job identification can be used by uustat to obtain the status or terminate a job.
Do not notify the user if the command fails.


The following operands are supported:
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 is interpreted as the local system.


The standard input is not used unless the - or -p option is specified; in those cases, the standard input is made the standard input of the command-string.


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


The following environment variables affect the execution of uux:
Provide a default value for the internationalisation variables that are unset or null. If LANG is unset or null, the corresponding value from the implementation-dependent default locale will be used. If any of the internationalisation variables contains an invalid setting, the utility will behave as if none of the variables had been defined.
If set to a non-empty string value, override the values of all the other internationalisation variables.
Determine the locale for the interpretation of sequences of bytes of text data as characters (for example, single- as opposed to multi-byte characters in arguments).
Determine the locale that should be used to affect the format and contents of diagnostic messages written to standard error.
Determine the location of message catalogues for the processing of LC_MESSAGES .




The standard output is not used unless the -j option is specified; in that case, the job identification string is written to standard output in the following format:

"%s\n", <jobid>


Used only for diagnostic messages.


Output files are created or written, or both, according to the contents of command-string.

If the -n is not used, mail files will be modified following any command or file-access failures on the remote system.




The following exit values are returned:
Successful completion.
An error occurred.




Note that, for security reasons, many installations will limit the list of commands executable on behalf of an incoming request from uux. Many sites will 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-internationalised systems.


  1. The following command gets file1 from system a and file2 file 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 will fail 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 will conflict.
    uux "!diff a!/usr1/xyz b!/usr2/xyz >!~/xyz.diff"

  3. The following command will succeed (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 the file from system c.
    uux "a!diff a!/usr/xyz c!/usr/xyz >!~/xyz.diff"


A version of uux that fully supports the XBD specification, Utility Syntax Guidelines  may be introduced in a future issue.


uucp, uuencode, uustat.

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Copyright © 1997 The Open Group
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