This XQuery Module provides functions for executing system commands from XQuery.
Conventions
All functions and errors in this module are assigned to the http://basex.org/modules/proc
namespace, which is statically bound to the proc
prefix.
Functions
proc:system
Signatures
|
proc:system($cmd as xs:string) as xs:string
proc:system($cmd as xs:string, $args as xs:string*) as xs:string
proc:system($cmd as xs:string, $args as xs:string*, $options as map(xs:string, xs:string)) as xs:string
|
Summary
|
Executes the specified command in a separate process and returns the result as string. $cmd is the name of the command, arguments to the command may be specified via $args . The $options parameter contains process options:
encoding : convert result to the specified encoding. If no encoding is supplied, the system’s default encoding is used.
timeout : abort process execution after the specified number of seconds.
dir : process command in the specified directory.
input : standard string input (stdin ) to be passed on to the command.
|
Errors
|
encoding : the specified encoding does not exist or is not supported.
timeout : the specified timeout was exceeded.
error : the command could not be executed, or an I/O exception was raised.
code.... : If the commands returns an exit code different to 0, an error will be raised. Its code will consist of the letters code and four digits with the exit code.
|
Examples
|
proc:system('date') returns the current date on a Linux system.
- Analyses the given input and counts the number of lines, words and characters (provided that
wc is available on the system):
proc:system(
'wc', (),
map { 'input': 'A B' || out:nl() || 'C' }
)
- The following example returns “Command not found” (unless
xyz is a valid command on the system):
try {
proc:system('xyz')
} catch proc:error {
'Command not found: ' || $err:description
}
|
proc:execute
Signatures
|
proc:execute($cmd as xs:string) as element(result)
proc:execute($cmd as xs:string, $args as xs:string*) as element(result)
proc:execute($cmd as xs:string, $args as xs:string*, $options as map(xs:string, xs:string)) as element(result)
|
Summary
|
Executes the specified command in a separate process and returns the result as element:
$cmd is the name of the command, and arguments to the command may be specified via $args .
- The same
$options are allowed as for proc:system.
- Instead of the
proc:error error, the error message and process code will be assigned to the returned elements.
- Instead of the
proc:code.... error, the error message will be assigned to the returned element (no process code will be returned).
The result has the following structure:
<result>
<output>...output...</output>
<error>...error message...</error>
<code>...process code...</code>
</result>
|
Errors
|
encoding : the specified encoding does not exist or is not supported.
timeout : the specified timeout was exceeded.
|
Examples
|
proc:execute('dir', '\') returns the files of the root directory of a Windows system.
proc:execute('ls', ('-l', '-a')) executes the ls -la command on Unix systems.
|
proc:fork
Signatures
|
proc:fork($cmd as xs:string) as element(result)
proc:fork($cmd as xs:string, $args as xs:string*) as element(result)
proc:fork($cmd as xs:string, $args as xs:string*, $options as map(xs:string, xs:string)) as element(result)
|
Summary
|
Executes the specified command and ignores the result. $cmd is the name of the command, and arguments to the command may be specified via $args . The same $options are allowed as for proc:system (but the encoding will be ignored).
|
Errors
|
encoding : the specified encoding does not exist or is not supported.
|
Examples
|
proc:fork('sleep', '5') : sleep for 5 seconds (no one should notice).
|
proc:property
Signatures
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proc:property($name as xs:string) as xs:string?
|
Summary
|
Returns the system property, specified by $name , or a context parameter of the web.xml file with that name (see Web Applications). An empty sequence is returned if the property does not exist. For environment variables of the operating system, please use fn:environment-variable.
|
Examples
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map:merge(proc:property-names() ! map:entry(., proc:property(.))) returns a map with all system properties.
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proc:property-names
Signatures
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proc:property-names() as xs:string*
|
Summary
|
Returns the names of all Java system properties and context parameters of the web.xml file (see Web Applications). For environment variables of the operating system, please use fn:available-environment-variables.
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Examples
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proc:property('java.runtime.version') returns the version of the Java runtime engine.
|
Errors
Code
|
Description
|
code...
|
The result of a command call with an exit code different to 0.
|
code9999
|
A command could not be executed.
|
encoding
|
The specified encoding does not exist or is not supported.
|
timeout
|
The specified timeout was exceeded.
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Changelog
- Version 9.0
- Added: proc:fork
- Updated: error codes; errors now use the module namespace
- Updated: new
input
option; revised error handling
- Version 8.6
- Updated: proc:system, proc:exec:
encoding
option moved to options argument, timeout
and dir
options added.
- Version 8.3
The module was introduced with Version 7.3.