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| 55 | <H2><A NAME="SECTION008120000000000000000"></A><A NAME="os-newstreams"></A> |
| 56 | <BR> |
| 57 | 6.1.2 File Object Creation |
| 58 | </H2> |
| 59 | |
| 60 | <P> |
| 61 | These functions create new file objects. |
| 62 | |
| 63 | <P> |
| 64 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 65 | <td><nobr><b><tt id='l2h-1551' xml:id='l2h-1551' class="function">fdopen</tt></b>(</nobr></td> |
| 66 | <td><var>fd</var><big>[</big><var>, mode</var><big>[</big><var>, bufsize</var><big>]</big><var></var><big>]</big><var></var>)</td></tr></table></dt> |
| 67 | <dd> |
| 68 | Return an open file object connected to the file descriptor <var>fd</var>. |
| 69 | <a id='l2h-1557' xml:id='l2h-1557'></a> |
| 70 | The <var>mode</var> and <var>bufsize</var> arguments have the same meaning as |
| 71 | the corresponding arguments to the built-in <tt class="function">open()</tt> |
| 72 | function. |
| 73 | Availability: Macintosh, <span class="Unix">Unix</span>, Windows. |
| 74 | |
| 75 | <P> |
| 76 | |
| 77 | <span class="versionnote">Changed in version 2.3: |
| 78 | When specified, the <var>mode</var> argument must now start |
| 79 | with one of the letters "<tt class="character">r</tt>", "<tt class="character">w</tt>", or "<tt class="character">a</tt>", |
| 80 | otherwise a <tt class="exception">ValueError</tt> is raised.</span> |
| 81 | |
| 82 | </dl> |
| 83 | |
| 84 | <P> |
| 85 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 86 | <td><nobr><b><tt id='l2h-1552' xml:id='l2h-1552' class="function">popen</tt></b>(</nobr></td> |
| 87 | <td><var>command</var><big>[</big><var>, mode</var><big>[</big><var>, bufsize</var><big>]</big><var></var><big>]</big><var></var>)</td></tr></table></dt> |
| 88 | <dd> |
| 89 | Open a pipe to or from <var>command</var>. The return value is an open |
| 90 | file object connected to the pipe, which can be read or written |
| 91 | depending on whether <var>mode</var> is <code>'r'</code> (default) or <code>'w'</code>. |
| 92 | The <var>bufsize</var> argument has the same meaning as the corresponding |
| 93 | argument to the built-in <tt class="function">open()</tt> function. The exit status of |
| 94 | the command (encoded in the format specified for <tt class="function">wait()</tt>) is |
| 95 | available as the return value of the <tt class="method">close()</tt> method of the file |
| 96 | object, except that when the exit status is zero (termination without |
| 97 | errors), <code>None</code> is returned. |
| 98 | Availability: Macintosh, <span class="Unix">Unix</span>, Windows. |
| 99 | |
| 100 | <P> |
| 101 | |
| 102 | <span class="versionnote">Changed in version 2.0: |
| 103 | This function worked unreliably under Windows in |
| 104 | earlier versions of Python. This was due to the use of the |
| 105 | <tt class="cfunction">_popen()</tt> function from the libraries provided with |
| 106 | Windows. Newer versions of Python do not use the broken |
| 107 | implementation from the Windows libraries.</span> |
| 108 | |
| 109 | </dl> |
| 110 | |
| 111 | <P> |
| 112 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 113 | <td><nobr><b><tt id='l2h-1553' xml:id='l2h-1553' class="function">tmpfile</tt></b>(</nobr></td> |
| 114 | <td><var></var>)</td></tr></table></dt> |
| 115 | <dd> |
| 116 | Return a new file object opened in update mode ("<tt class="samp">w+b</tt>"). The file |
| 117 | has no directory entries associated with it and will be automatically |
| 118 | deleted once there are no file descriptors for the file. |
| 119 | Availability: Macintosh, <span class="Unix">Unix</span>, Windows. |
| 120 | </dl> |
| 121 | |
| 122 | <P> |
| 123 | For each of the following <tt class="function">popen()</tt> variants, if <var>bufsize</var> is |
| 124 | specified, it specifies the buffer size for the I/O pipes. |
| 125 | <var>mode</var>, if provided, should be the string <code>'b'</code> or |
| 126 | <code>'t'</code>; on Windows this is needed to determine whether the file |
| 127 | objects should be opened in binary or text mode. The default value |
| 128 | for <var>mode</var> is <code>'t'</code>. |
| 129 | |
| 130 | <P> |
| 131 | Also, for each of these variants, on <span class="Unix">Unix</span>, <var>cmd</var> may be a sequence, in |
| 132 | which case arguments will be passed directly to the program without shell |
| 133 | intervention (as with <tt class="function">os.spawnv()</tt>). If <var>cmd</var> is a string it will |
| 134 | be passed to the shell (as with <tt class="function">os.system()</tt>). |
| 135 | |
| 136 | <P> |
| 137 | These methods do not make it possible to retrieve the exit status from |
| 138 | the child processes. The only way to control the input and output |
| 139 | streams and also retrieve the return codes is to use the |
| 140 | <tt class="class">Popen3</tt> and <tt class="class">Popen4</tt> classes from the <tt class="module"><a href="module-popen2.html">popen2</a></tt> |
| 141 | module; these are only available on <span class="Unix">Unix</span>. |
| 142 | |
| 143 | <P> |
| 144 | For a discussion of possible deadlock conditions related to the use |
| 145 | of these functions, see ``<a class="ulink" href="popen2-flow-control.html" |
| 146 | >Flow Control |
| 147 | Issues</a>'' |
| 148 | (section <A href="popen2-flow-control.html#popen2-flow-control">6.9.2</A>). |
| 149 | |
| 150 | <P> |
| 151 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 152 | <td><nobr><b><tt id='l2h-1554' xml:id='l2h-1554' class="function">popen2</tt></b>(</nobr></td> |
| 153 | <td><var>cmd</var><big>[</big><var>, mode</var><big>[</big><var>, bufsize</var><big>]</big><var></var><big>]</big><var></var>)</td></tr></table></dt> |
| 154 | <dd> |
| 155 | Executes <var>cmd</var> as a sub-process. Returns the file objects |
| 156 | <code>(<var>child_stdin</var>, <var>child_stdout</var>)</code>. |
| 157 | Availability: Macintosh, <span class="Unix">Unix</span>, Windows. |
| 158 | |
| 159 | <span class="versionnote">New in version 2.0.</span> |
| 160 | |
| 161 | </dl> |
| 162 | |
| 163 | <P> |
| 164 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 165 | <td><nobr><b><tt id='l2h-1555' xml:id='l2h-1555' class="function">popen3</tt></b>(</nobr></td> |
| 166 | <td><var>cmd</var><big>[</big><var>, mode</var><big>[</big><var>, bufsize</var><big>]</big><var></var><big>]</big><var></var>)</td></tr></table></dt> |
| 167 | <dd> |
| 168 | Executes <var>cmd</var> as a sub-process. Returns the file objects |
| 169 | <code>(<var>child_stdin</var>, <var>child_stdout</var>, <var>child_stderr</var>)</code>. |
| 170 | Availability: Macintosh, <span class="Unix">Unix</span>, Windows. |
| 171 | |
| 172 | <span class="versionnote">New in version 2.0.</span> |
| 173 | |
| 174 | </dl> |
| 175 | |
| 176 | <P> |
| 177 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 178 | <td><nobr><b><tt id='l2h-1556' xml:id='l2h-1556' class="function">popen4</tt></b>(</nobr></td> |
| 179 | <td><var>cmd</var><big>[</big><var>, mode</var><big>[</big><var>, bufsize</var><big>]</big><var></var><big>]</big><var></var>)</td></tr></table></dt> |
| 180 | <dd> |
| 181 | Executes <var>cmd</var> as a sub-process. Returns the file objects |
| 182 | <code>(<var>child_stdin</var>, <var>child_stdout_and_stderr</var>)</code>. |
| 183 | Availability: Macintosh, <span class="Unix">Unix</span>, Windows. |
| 184 | |
| 185 | <span class="versionnote">New in version 2.0.</span> |
| 186 | |
| 187 | </dl> |
| 188 | |
| 189 | <P> |
| 190 | (Note that <code><var>child_stdin</var>, <var>child_stdout</var>, and |
| 191 | <var>child_stderr</var></code> are named from the point of view of the child |
| 192 | process, i.e. <var>child_stdin</var> is the child's standard input.) |
| 193 | |
| 194 | <P> |
| 195 | This functionality is also available in the <tt class="module"><a href="module-popen2.html">popen2</a></tt> module |
| 196 | using functions of the same names, but the return values of those |
| 197 | functions have a different order. |
| 198 | |
| 199 | <P> |
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