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| 17 | <title>6.1.1 Process Parameters </title> |
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| 55 | <H2><A NAME="SECTION008110000000000000000"></A><A NAME="os-procinfo"></A> |
| 56 | <BR> |
| 57 | 6.1.1 Process Parameters |
| 58 | </H2> |
| 59 | |
| 60 | <P> |
| 61 | These functions and data items provide information and operate on the |
| 62 | current process and user. |
| 63 | |
| 64 | <P> |
| 65 | <dl><dt><b><tt id='l2h-1508' xml:id='l2h-1508'>environ</tt></b></dt> |
| 66 | <dd> |
| 67 | A mapping object representing the string environment. For example, |
| 68 | <code>environ['HOME']</code> is the pathname of your home directory (on some |
| 69 | platforms), and is equivalent to <code>getenv("HOME")</code> in C. |
| 70 | |
| 71 | <P> |
| 72 | This mapping is captured the first time the <tt class="module">os</tt> module is |
| 73 | imported, typically during Python startup as part of processing |
| 74 | <span class="file">site.py</span>. Changes to the environment made after this time are |
| 75 | not reflected in <code>os.environ</code>, except for changes made by modifying |
| 76 | <code>os.environ</code> directly. |
| 77 | |
| 78 | <P> |
| 79 | If the platform supports the <tt class="function">putenv()</tt> function, this |
| 80 | mapping may be used to modify the environment as well as query the |
| 81 | environment. <tt class="function">putenv()</tt> will be called automatically when |
| 82 | the mapping is modified. |
| 83 | <span class="note"><b class="label">Note:</b> |
| 84 | Calling <tt class="function">putenv()</tt> directly does not change |
| 85 | <code>os.environ</code>, so it's better to modify <code>os.environ</code>.</span> |
| 86 | <span class="note"><b class="label">Note:</b> |
| 87 | On some platforms, including FreeBSD and Mac OS X, setting |
| 88 | <code>environ</code> may cause memory leaks. Refer to the system documentation |
| 89 | for <tt class="cfunction">putenv()</tt>.</span> |
| 90 | |
| 91 | <P> |
| 92 | If <tt class="function">putenv()</tt> is not provided, a modified copy of this mapping |
| 93 | may be passed to the appropriate process-creation functions to cause |
| 94 | child processes to use a modified environment. |
| 95 | |
| 96 | <P> |
| 97 | If the platform supports the <tt class="function">unsetenv()</tt> function, you can |
| 98 | delete items in this mapping to unset environment variables. |
| 99 | <tt class="function">unsetenv()</tt> will be called automatically when an item is |
| 100 | deleted from <code>os.environ</code>. |
| 101 | |
| 102 | <P> |
| 103 | </dd></dl> |
| 104 | |
| 105 | <P> |
| 106 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 107 | <td><nobr><b><tt class="function">chdir</tt></b>(</nobr></td> |
| 108 | <td><var>path</var>)</td></tr></table></dt> |
| 109 | <dd> |
| 110 | <dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 111 | <td><nobr><b><tt class="function">fchdir</tt></b>(</nobr></td> |
| 112 | <td><var>fd</var>)</td></tr></table></dt> |
| 113 | <dd><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 114 | <td><nobr><b><tt class="function">getcwd</tt></b>(</nobr></td> |
| 115 | <td><var></var>)</td></tr></table></dt> |
| 116 | <dd>These functions are described in ``Files and Directories'' (section |
| 117 | <A href="os-file-dir.html#os-file-dir">6.1.4</A>). |
| 118 | </dl> |
| 119 | |
| 120 | <P> |
| 121 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 122 | <td><nobr><b><tt id='l2h-1509' xml:id='l2h-1509' class="function">ctermid</tt></b>(</nobr></td> |
| 123 | <td><var></var>)</td></tr></table></dt> |
| 124 | <dd> |
| 125 | Return the filename corresponding to the controlling terminal of the |
| 126 | process. |
| 127 | Availability: <span class="Unix">Unix</span>. |
| 128 | </dl> |
| 129 | |
| 130 | <P> |
| 131 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 132 | <td><nobr><b><tt id='l2h-1510' xml:id='l2h-1510' class="function">getegid</tt></b>(</nobr></td> |
| 133 | <td><var></var>)</td></tr></table></dt> |
| 134 | <dd> |
| 135 | Return the effective group id of the current process. This |
| 136 | corresponds to the `set id' bit on the file being executed in the |
| 137 | current process. |
| 138 | Availability: <span class="Unix">Unix</span>. |
| 139 | </dl> |
| 140 | |
| 141 | <P> |
| 142 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 143 | <td><nobr><b><tt id='l2h-1511' xml:id='l2h-1511' class="function">geteuid</tt></b>(</nobr></td> |
| 144 | <td><var></var>)</td></tr></table></dt> |
| 145 | <dd> |
| 146 | <a id='l2h-1541' xml:id='l2h-1541'></a> |
| 147 | Return the current process' effective user id. |
| 148 | Availability: <span class="Unix">Unix</span>. |
| 149 | </dl> |
| 150 | |
| 151 | <P> |
| 152 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 153 | <td><nobr><b><tt id='l2h-1512' xml:id='l2h-1512' class="function">getgid</tt></b>(</nobr></td> |
| 154 | <td><var></var>)</td></tr></table></dt> |
| 155 | <dd> |
| 156 | <a id='l2h-1542' xml:id='l2h-1542'></a> |
| 157 | Return the real group id of the current process. |
| 158 | Availability: <span class="Unix">Unix</span>. |
| 159 | </dl> |
| 160 | |
| 161 | <P> |
| 162 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 163 | <td><nobr><b><tt id='l2h-1513' xml:id='l2h-1513' class="function">getgroups</tt></b>(</nobr></td> |
| 164 | <td><var></var>)</td></tr></table></dt> |
| 165 | <dd> |
| 166 | Return list of supplemental group ids associated with the current |
| 167 | process. |
| 168 | Availability: <span class="Unix">Unix</span>. |
| 169 | </dl> |
| 170 | |
| 171 | <P> |
| 172 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 173 | <td><nobr><b><tt id='l2h-1514' xml:id='l2h-1514' class="function">getlogin</tt></b>(</nobr></td> |
| 174 | <td><var></var>)</td></tr></table></dt> |
| 175 | <dd> |
| 176 | Return the name of the user logged in on the controlling terminal of |
| 177 | the process. For most purposes, it is more useful to use the |
| 178 | environment variable <a class="envvar" id='l2h-1543' xml:id='l2h-1543'>LOGNAME</a> to find out who the user is, |
| 179 | or <code>pwd.getpwuid(os.getuid())[0]</code> to get the login name |
| 180 | of the currently effective user ID. |
| 181 | Availability: <span class="Unix">Unix</span>. |
| 182 | </dl> |
| 183 | |
| 184 | <P> |
| 185 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 186 | <td><nobr><b><tt id='l2h-1515' xml:id='l2h-1515' class="function">getpgid</tt></b>(</nobr></td> |
| 187 | <td><var>pid</var>)</td></tr></table></dt> |
| 188 | <dd> |
| 189 | Return the process group id of the process with process id <var>pid</var>. |
| 190 | If <var>pid</var> is 0, the process group id of the current process is |
| 191 | returned. Availability: <span class="Unix">Unix</span>. |
| 192 | |
| 193 | <span class="versionnote">New in version 2.3.</span> |
| 194 | |
| 195 | </dl> |
| 196 | |
| 197 | <P> |
| 198 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 199 | <td><nobr><b><tt id='l2h-1516' xml:id='l2h-1516' class="function">getpgrp</tt></b>(</nobr></td> |
| 200 | <td><var></var>)</td></tr></table></dt> |
| 201 | <dd> |
| 202 | <a id='l2h-1544' xml:id='l2h-1544'></a> |
| 203 | Return the id of the current process group. |
| 204 | Availability: <span class="Unix">Unix</span>. |
| 205 | </dl> |
| 206 | |
| 207 | <P> |
| 208 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 209 | <td><nobr><b><tt id='l2h-1517' xml:id='l2h-1517' class="function">getpid</tt></b>(</nobr></td> |
| 210 | <td><var></var>)</td></tr></table></dt> |
| 211 | <dd> |
| 212 | <a id='l2h-1545' xml:id='l2h-1545'></a> |
| 213 | Return the current process id. |
| 214 | Availability: <span class="Unix">Unix</span>, Windows. |
| 215 | </dl> |
| 216 | |
| 217 | <P> |
| 218 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 219 | <td><nobr><b><tt id='l2h-1518' xml:id='l2h-1518' class="function">getppid</tt></b>(</nobr></td> |
| 220 | <td><var></var>)</td></tr></table></dt> |
| 221 | <dd> |
| 222 | <a id='l2h-1546' xml:id='l2h-1546'></a> |
| 223 | Return the parent's process id. |
| 224 | Availability: <span class="Unix">Unix</span>. |
| 225 | </dl> |
| 226 | |
| 227 | <P> |
| 228 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 229 | <td><nobr><b><tt id='l2h-1519' xml:id='l2h-1519' class="function">getuid</tt></b>(</nobr></td> |
| 230 | <td><var></var>)</td></tr></table></dt> |
| 231 | <dd> |
| 232 | <a id='l2h-1547' xml:id='l2h-1547'></a> |
| 233 | Return the current process' user id. |
| 234 | Availability: <span class="Unix">Unix</span>. |
| 235 | </dl> |
| 236 | |
| 237 | <P> |
| 238 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 239 | <td><nobr><b><tt id='l2h-1520' xml:id='l2h-1520' class="function">getenv</tt></b>(</nobr></td> |
| 240 | <td><var>varname</var><big>[</big><var>, value</var><big>]</big><var></var>)</td></tr></table></dt> |
| 241 | <dd> |
| 242 | Return the value of the environment variable <var>varname</var> if it |
| 243 | exists, or <var>value</var> if it doesn't. <var>value</var> defaults to |
| 244 | <code>None</code>. |
| 245 | Availability: most flavors of <span class="Unix">Unix</span>, Windows. |
| 246 | </dl> |
| 247 | |
| 248 | <P> |
| 249 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 250 | <td><nobr><b><tt id='l2h-1521' xml:id='l2h-1521' class="function">putenv</tt></b>(</nobr></td> |
| 251 | <td><var>varname, value</var>)</td></tr></table></dt> |
| 252 | <dd> |
| 253 | <a id='l2h-1548' xml:id='l2h-1548'></a> |
| 254 | Set the environment variable named <var>varname</var> to the string |
| 255 | <var>value</var>. Such changes to the environment affect subprocesses |
| 256 | started with <tt class="function">os.system()</tt>, <tt class="function">popen()</tt> or |
| 257 | <tt class="function">fork()</tt> and <tt class="function">execv()</tt>. |
| 258 | Availability: most flavors of <span class="Unix">Unix</span>, Windows. |
| 259 | |
| 260 | <P> |
| 261 | <span class="note"><b class="label">Note:</b> |
| 262 | On some platforms, including FreeBSD and Mac OS X, |
| 263 | setting <code>environ</code> may cause memory leaks. |
| 264 | Refer to the system documentation for putenv.</span> |
| 265 | |
| 266 | <P> |
| 267 | When <tt class="function">putenv()</tt> is |
| 268 | supported, assignments to items in <code>os.environ</code> are automatically |
| 269 | translated into corresponding calls to <tt class="function">putenv()</tt>; however, |
| 270 | calls to <tt class="function">putenv()</tt> don't update <code>os.environ</code>, so it is |
| 271 | actually preferable to assign to items of <code>os.environ</code>. |
| 272 | </dl> |
| 273 | |
| 274 | <P> |
| 275 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 276 | <td><nobr><b><tt id='l2h-1522' xml:id='l2h-1522' class="function">setegid</tt></b>(</nobr></td> |
| 277 | <td><var>egid</var>)</td></tr></table></dt> |
| 278 | <dd> |
| 279 | Set the current process's effective group id. |
| 280 | Availability: <span class="Unix">Unix</span>. |
| 281 | </dl> |
| 282 | |
| 283 | <P> |
| 284 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 285 | <td><nobr><b><tt id='l2h-1523' xml:id='l2h-1523' class="function">seteuid</tt></b>(</nobr></td> |
| 286 | <td><var>euid</var>)</td></tr></table></dt> |
| 287 | <dd> |
| 288 | Set the current process's effective user id. |
| 289 | Availability: <span class="Unix">Unix</span>. |
| 290 | </dl> |
| 291 | |
| 292 | <P> |
| 293 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 294 | <td><nobr><b><tt id='l2h-1524' xml:id='l2h-1524' class="function">setgid</tt></b>(</nobr></td> |
| 295 | <td><var>gid</var>)</td></tr></table></dt> |
| 296 | <dd> |
| 297 | Set the current process' group id. |
| 298 | Availability: <span class="Unix">Unix</span>. |
| 299 | </dl> |
| 300 | |
| 301 | <P> |
| 302 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 303 | <td><nobr><b><tt id='l2h-1525' xml:id='l2h-1525' class="function">setgroups</tt></b>(</nobr></td> |
| 304 | <td><var>groups</var>)</td></tr></table></dt> |
| 305 | <dd> |
| 306 | Set the list of supplemental group ids associated with the current |
| 307 | process to <var>groups</var>. <var>groups</var> must be a sequence, and each |
| 308 | element must be an integer identifying a group. This operation is |
| 309 | typical available only to the superuser. |
| 310 | Availability: <span class="Unix">Unix</span>. |
| 311 | |
| 312 | <span class="versionnote">New in version 2.2.</span> |
| 313 | |
| 314 | </dl> |
| 315 | |
| 316 | <P> |
| 317 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 318 | <td><nobr><b><tt id='l2h-1526' xml:id='l2h-1526' class="function">setpgrp</tt></b>(</nobr></td> |
| 319 | <td><var></var>)</td></tr></table></dt> |
| 320 | <dd> |
| 321 | Calls the system call <tt class="cfunction">setpgrp()</tt> or <tt class="cfunction">setpgrp(0, |
| 322 | 0)</tt> depending on which version is implemented (if any). See the |
| 323 | <span class="Unix">Unix</span> manual for the semantics. |
| 324 | Availability: <span class="Unix">Unix</span>. |
| 325 | </dl> |
| 326 | |
| 327 | <P> |
| 328 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 329 | <td><nobr><b><tt id='l2h-1527' xml:id='l2h-1527' class="function">setpgid</tt></b>(</nobr></td> |
| 330 | <td><var>pid, pgrp</var>)</td></tr></table></dt> |
| 331 | <dd> Calls the system call |
| 332 | <tt class="cfunction">setpgid()</tt> to set the process group id of the process with |
| 333 | id <var>pid</var> to the process group with id <var>pgrp</var>. See the <span class="Unix">Unix</span> |
| 334 | manual for the semantics. |
| 335 | Availability: <span class="Unix">Unix</span>. |
| 336 | </dl> |
| 337 | |
| 338 | <P> |
| 339 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 340 | <td><nobr><b><tt id='l2h-1528' xml:id='l2h-1528' class="function">setreuid</tt></b>(</nobr></td> |
| 341 | <td><var>ruid, euid</var>)</td></tr></table></dt> |
| 342 | <dd> |
| 343 | Set the current process's real and effective user ids. |
| 344 | Availability: <span class="Unix">Unix</span>. |
| 345 | </dl> |
| 346 | |
| 347 | <P> |
| 348 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 349 | <td><nobr><b><tt id='l2h-1529' xml:id='l2h-1529' class="function">setregid</tt></b>(</nobr></td> |
| 350 | <td><var>rgid, egid</var>)</td></tr></table></dt> |
| 351 | <dd> |
| 352 | Set the current process's real and effective group ids. |
| 353 | Availability: <span class="Unix">Unix</span>. |
| 354 | </dl> |
| 355 | |
| 356 | <P> |
| 357 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 358 | <td><nobr><b><tt id='l2h-1530' xml:id='l2h-1530' class="function">getsid</tt></b>(</nobr></td> |
| 359 | <td><var>pid</var>)</td></tr></table></dt> |
| 360 | <dd> |
| 361 | Calls the system call <tt class="cfunction">getsid()</tt>. See the <span class="Unix">Unix</span> manual |
| 362 | for the semantics. |
| 363 | Availability: <span class="Unix">Unix</span>. |
| 364 | <span class="versionnote">New in version 2.4.</span> |
| 365 | |
| 366 | </dl> |
| 367 | |
| 368 | <P> |
| 369 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 370 | <td><nobr><b><tt id='l2h-1531' xml:id='l2h-1531' class="function">setsid</tt></b>(</nobr></td> |
| 371 | <td><var></var>)</td></tr></table></dt> |
| 372 | <dd> |
| 373 | Calls the system call <tt class="cfunction">setsid()</tt>. See the <span class="Unix">Unix</span> manual |
| 374 | for the semantics. |
| 375 | Availability: <span class="Unix">Unix</span>. |
| 376 | </dl> |
| 377 | |
| 378 | <P> |
| 379 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 380 | <td><nobr><b><tt id='l2h-1532' xml:id='l2h-1532' class="function">setuid</tt></b>(</nobr></td> |
| 381 | <td><var>uid</var>)</td></tr></table></dt> |
| 382 | <dd> |
| 383 | <a id='l2h-1549' xml:id='l2h-1549'></a> |
| 384 | Set the current process' user id. |
| 385 | Availability: <span class="Unix">Unix</span>. |
| 386 | </dl> |
| 387 | |
| 388 | <P> |
| 389 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 390 | <td><nobr><b><tt id='l2h-1533' xml:id='l2h-1533' class="function">strerror</tt></b>(</nobr></td> |
| 391 | <td><var>code</var>)</td></tr></table></dt> |
| 392 | <dd> |
| 393 | Return the error message corresponding to the error code in |
| 394 | <var>code</var>. |
| 395 | Availability: <span class="Unix">Unix</span>, Windows. |
| 396 | </dl> |
| 397 | |
| 398 | <P> |
| 399 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 400 | <td><nobr><b><tt id='l2h-1534' xml:id='l2h-1534' class="function">umask</tt></b>(</nobr></td> |
| 401 | <td><var>mask</var>)</td></tr></table></dt> |
| 402 | <dd> |
| 403 | Set the current numeric umask and returns the previous umask. |
| 404 | Availability: <span class="Unix">Unix</span>, Windows. |
| 405 | </dl> |
| 406 | |
| 407 | <P> |
| 408 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 409 | <td><nobr><b><tt id='l2h-1535' xml:id='l2h-1535' class="function">uname</tt></b>(</nobr></td> |
| 410 | <td><var></var>)</td></tr></table></dt> |
| 411 | <dd> |
| 412 | Return a 5-tuple containing information identifying the current |
| 413 | operating system. The tuple contains 5 strings: |
| 414 | <code>(<var>sysname</var>, <var>nodename</var>, <var>release</var>, <var>version</var>, |
| 415 | <var>machine</var>)</code>. Some systems truncate the nodename to 8 |
| 416 | characters or to the leading component; a better way to get the |
| 417 | hostname is <tt class="function">socket.gethostname()</tt> |
| 418 | <a id='l2h-1537' xml:id='l2h-1537'></a>or even |
| 419 | <a id='l2h-1539' xml:id='l2h-1539'></a><code>socket.gethostbyaddr(socket.gethostname())</code>. |
| 420 | Availability: recent flavors of <span class="Unix">Unix</span>. |
| 421 | </dl> |
| 422 | |
| 423 | <P> |
| 424 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 425 | <td><nobr><b><tt id='l2h-1540' xml:id='l2h-1540' class="function">unsetenv</tt></b>(</nobr></td> |
| 426 | <td><var>varname</var>)</td></tr></table></dt> |
| 427 | <dd> |
| 428 | <a id='l2h-1550' xml:id='l2h-1550'></a> |
| 429 | Unset (delete) the environment variable named <var>varname</var>. Such |
| 430 | changes to the environment affect subprocesses started with |
| 431 | <tt class="function">os.system()</tt>, <tt class="function">popen()</tt> or <tt class="function">fork()</tt> and |
| 432 | <tt class="function">execv()</tt>. Availability: most flavors of <span class="Unix">Unix</span>, Windows. |
| 433 | |
| 434 | <P> |
| 435 | When <tt class="function">unsetenv()</tt> is |
| 436 | supported, deletion of items in <code>os.environ</code> is automatically |
| 437 | translated into a corresponding call to <tt class="function">unsetenv()</tt>; however, |
| 438 | calls to <tt class="function">unsetenv()</tt> don't update <code>os.environ</code>, so it is |
| 439 | actually preferable to delete items of <code>os.environ</code>. |
| 440 | </dl> |
| 441 | |
| 442 | <P> |
| 443 | |
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| 478 | <span class="release-info">Release 2.4.2, documentation updated on 28 September 2005.</span> |
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