| \section{\module{popen2} --- |
| Subprocesses with accessible standard I/O streams} |
| |
| \declaremodule[popentwo]{standard}{popen2} |
| \platform{Unix} |
| \modulesynopsis{Subprocesses with accessible standard I/O streams.} |
| \sectionauthor{Drew Csillag}{drew_csillag@geocities.com} |
| |
| |
| This module allows you to spawn processes and connect their |
| input/output/error pipes and obtain their return codes. |
| |
| The primary interface offered by this module is a pair of factory |
| functions: |
| |
| \begin{funcdesc}{popen2}{cmd\optional{, bufsize}} |
| Executes \var{cmd} as a sub-process. If \var{bufsize} is specified, |
| it specifies the buffer size for the I/O pipes. Returns |
| \code{(\var{child_stdout}, \var{child_stdin})}. |
| \end{funcdesc} |
| |
| \begin{funcdesc}{popen3}{cmd\optional{, bufsize}} |
| Executes \var{cmd} as a sub-process. If \var{bufsize} is specified, |
| it specifies the buffer size for the I/O pipes. Returns |
| \code{(\var{child_stdout}, \var{child_stdin}, \var{child_stderr})}. |
| \end{funcdesc} |
| |
| The class defining the objects returned by the factory functions is |
| also available: |
| |
| \begin{classdesc}{Popen3}{cmd\optional{, capturestderr\optional{, bufsize}}} |
| This class represents a child process. Normally, \class{Popen3} |
| instances are created using the factory functions described above. |
| |
| If not using one off the helper functions to create \class{Popen3} |
| objects, the parameter \var{cmd} is the shell command to execute in a |
| sub-process. The \var{capturestderr} flag, if true, specifies that |
| the object should capture standard error output of the child process. |
| The default is false. If the \var{bufsize} parameter is specified, it |
| specifies the size of the I/O buffers to/from the child process. |
| \end{classdesc} |
| |
| |
| \subsection{Popen3 Objects} |
| \label{popen3-objects} |
| |
| Instances of the \class{Popen3} class have the following methods: |
| |
| \begin{methoddesc}{poll}{} |
| Returns \code{-1} if child process hasn't completed yet, or its return |
| code otherwise. |
| \end{methoddesc} |
| |
| \begin{methoddesc}{wait}{} |
| Waits for and returns the return code of the child process. |
| \end{methoddesc} |
| |
| |
| The following attributes of \class{Popen3} objects are also available: |
| |
| \begin{datadesc}{fromchild} |
| A file object that provides output from the child process. |
| \end{datadesc} |
| |
| \begin{datadesc}{tochild} |
| A file object that provides input to the child process. |
| \end{datadesc} |
| |
| \begin{datadesc}{childerr} |
| Where the standard error from the child process goes is |
| \var{capturestderr} was true for the constructor, or \code{None}. |
| \end{datadesc} |