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Initial commit of OpenSPARC T2 architecture model.
[OpenSPARC-T2-SAM] / sam-t2 / devtools / v8plus / html / python / lib / node235.html
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55<H2><A NAME="SECTION008810000000000000000">
566.8.1 Using the subprocess Module</A>
57</H2>
58
59<P>
60This module defines one class called <tt class="class">Popen</tt>:
61
62<P>
63<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
64 <td><nobr><b><span class="typelabel">class</span>&nbsp;<tt id='l2h-1833' xml:id='l2h-1833' class="class">Popen</tt></b>(</nobr></td>
65 <td><var>args, bufsize=0, executable=None,
66 stdin=None, stdout=None, stderr=None,
67 preexec_fn=None, close_fds=False, shell=False,
68 cwd=None, env=None, universal_newlines=False,
69 startupinfo=None, creationflags=0</var>)</td></tr></table></dt>
70<dd>
71
72<P>
73Arguments are:
74
75<P>
76<var>args</var> should be a string, or a sequence of program arguments. The
77program to execute is normally the first item in the args sequence or
78string, but can be explicitly set by using the executable argument.
79
80<P>
81On <span class="Unix">Unix</span>, with <var>shell=False</var> (default): In this case, the Popen
82class uses <tt class="method">os.execvp()</tt> to execute the child program.
83<var>args</var> should normally be a sequence. A string will be treated as a
84sequence with the string as the only item (the program to execute).
85
86<P>
87On <span class="Unix">Unix</span>, with <var>shell=True</var>: If args is a string, it specifies the
88command string to execute through the shell. If <var>args</var> is a
89sequence, the first item specifies the command string, and any
90additional items will be treated as additional shell arguments.
91
92<P>
93On Windows: the <tt class="class">Popen</tt> class uses CreateProcess() to execute
94the child program, which operates on strings. If <var>args</var> is a
95sequence, it will be converted to a string using the
96<tt class="method">list2cmdline</tt> method. Please note that not all MS Windows
97applications interpret the command line the same way:
98<tt class="method">list2cmdline</tt> is designed for applications using the same
99rules as the MS C runtime.
100
101<P>
102<var>bufsize</var>, if given, has the same meaning as the corresponding
103argument to the built-in open() function: <tt class="constant">0</tt> means unbuffered,
104<tt class="constant">1</tt> means line buffered, any other positive value means use a
105buffer of (approximately) that size. A negative <var>bufsize</var> means to
106use the system default, which usually means fully buffered. The default
107value for <var>bufsize</var> is <tt class="constant">0</tt> (unbuffered).
108
109<P>
110The <var>executable</var> argument specifies the program to execute. It is
111very seldom needed: Usually, the program to execute is defined by the
112<var>args</var> argument. If <var>shell=True</var>, the <var>executable</var>
113argument specifies which shell to use. On <span class="Unix">Unix</span>, the default shell
114is /bin/sh. On Windows, the default shell is specified by the COMSPEC
115environment variable.
116
117<P>
118<var>stdin</var>, <var>stdout</var> and <var>stderr</var> specify the executed
119programs' standard input, standard output and standard error file
120handles, respectively. Valid values are <code>PIPE</code>, an existing file
121descriptor (a positive integer), an existing file object, and
122<code>None</code>. <code>PIPE</code> indicates that a new pipe to the child
123should be created. With <code>None</code>, no redirection will occur; the
124child's file handles will be inherited from the parent. Additionally,
125<var>stderr</var> can be <code>STDOUT</code>, which indicates that the stderr
126data from the applications should be captured into the same file
127handle as for stdout.
128
129<P>
130If <var>preexec_fn</var> is set to a callable object, this object will be
131called in the child process just before the child is executed.
132
133<P>
134If <var>close_fds</var> is true, all file descriptors except <tt class="constant">0</tt>,
135<tt class="constant">1</tt> and <tt class="constant">2</tt> will be closed before the child process is
136executed.
137
138<P>
139If <var>shell</var> is <tt class="constant">True</tt>, the specified command will be
140executed through the shell.
141
142<P>
143If <var>cwd</var> is not <code>None</code>, the current directory will be changed
144to cwd before the child is executed.
145
146<P>
147If <var>env</var> is not <code>None</code>, it defines the environment variables
148for the new process.
149
150<P>
151If <var>universal_newlines</var> is <tt class="constant">True</tt>, the file objects stdout
152and stderr are opened as a text files, but lines may be terminated by
153any of <code>'&#92;n'</code>, the Unix end-of-line convention, <code>'&#92;r'</code>,
154the Macintosh convention or <code>'&#92;r&#92;n'</code>, the Windows convention.
155All of these external representations are seen as <code>'&#92;n'</code> by the
156Python program. <span class="note"><b class="label">Note:</b>
157This feature is only available if Python is built
158with universal newline support (the default). Also, the newlines
159attribute of the file objects <tt class="member">stdout</tt>, <tt class="member">stdin</tt> and
160<tt class="member">stderr</tt> are not updated by the communicate() method.</span>
161
162<P>
163The <var>startupinfo</var> and <var>creationflags</var>, if given, will be
164passed to the underlying CreateProcess() function. They can specify
165things such as appearance of the main window and priority for the new
166process. (Windows only)
167</dl>
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169<P>
170
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174<A NAME="CHILD_LINKS"><STRONG>Subsections</STRONG></a>
175
176<UL CLASS="ChildLinks">
177<LI><A href="node236.html">6.8.1.1 Convenience Functions</a>
178<LI><A href="node237.html">6.8.1.2 Exceptions</a>
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218<span class="release-info">Release 2.4.2, documentation updated on 28 September 2005.</span>
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Full OpenSPARC architecture tarball including simulator, hypervisor, and OBP.