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comparison: testing/mozbase/docs/mozprocess.rst

testing/mozbase/docs/mozprocess.rst

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1 :mod:`mozprocess` --- Launch and manage processes
2 =================================================
3
4 Mozprocess is a process-handling module that provides some additional
5 features beyond those available with python's subprocess:
6
7 * better handling of child processes, especially on Windows
8 * the ability to timeout the process after some absolute period, or some
9 period without any data written to stdout/stderr
10 * the ability to specify output handlers that will be called
11 for each line of output produced by the process
12 * the ability to specify handlers that will be called on process timeout
13 and normal process termination
14
15 Running a process
16 -----------------
17
18 mozprocess consists of two classes: ProcessHandler inherits from ProcessHandlerMixin.
19
20 Let's see how to run a process.
21 First, the class should be instanciated with at least one argument which is a command (or a list formed by the command followed by its arguments).
22 Then the process can be launched using the *run()* method.
23 Finally the *wait()* method will wait until end of execution.
24
25 .. code-block:: python
26
27 from mozprocess import processhandler
28
29 # under Windows replace by command = ['dir', '/a']
30 command = ['ls', '-l']
31 p = processhandler.ProcessHandler(command)
32 print("execute command: %s" % p.commandline)
33 p.run()
34 p.wait()
35
36 Note that using *ProcessHandler* instead of *ProcessHandlerMixin* will print the output of executed command. The attribute *commandline* provides the launched command.
37
38 Collecting process output
39 -------------------------
40
41 Let's now consider a basic shell script that will print numbers from 1 to 5 waiting 1 second between each.
42 This script will be used as a command to launch in further examples.
43
44 **proc_sleep_echo.sh**:
45
46 .. code-block:: sh
47
48 #!/bin/sh
49
50 for i in 1 2 3 4 5
51 do
52 echo $i
53 sleep 1
54 done
55
56 If you are running under Windows, you won't be able to use the previous script (unless using Cygwin).
57 So you'll use the following script:
58
59 **proc_sleep_echo.bat**:
60
61 .. code-block:: bat
62
63 @echo off
64 FOR %%A IN (1 2 3 4 5) DO (
65 ECHO %%A
66 REM if you have TIMEOUT then use it instead of PING
67 REM TIMEOUT /T 1 /NOBREAK
68 PING -n 2 127.0.0.1 > NUL
69 )
70
71 Mozprocess allows the specification of custom output handlers to gather process output while running.
72 ProcessHandler will by default write all outputs on stdout. You can also provide (to ProcessHandler or ProcessHandlerMixin) a function or a list of functions that will be used as callbacks on each output line generated by the process.
73
74 In the following example the command's output will be stored in a file *output.log* and printed in stdout:
75
76 .. code-block:: python
77
78 import sys
79 from mozprocess import processhandler
80
81 fd = open('output.log', 'w')
82
83 def tostdout(line):
84 sys.stdout.write("<%s>\n" % line)
85
86 def tofile(line):
87 fd.write("<%s>\n" % line)
88
89 # under Windows you'll replace by 'proc_sleep_echo.bat'
90 command = './proc_sleep_echo.sh'
91 outputs = [tostdout, tofile]
92
93 p = processhandler.ProcessHandlerMixin(command, processOutputLine=outputs)
94 p.run()
95 p.wait()
96
97 fd.close()
98
99 The process output can be saved (*obj = ProcessHandler(..., storeOutput=True)*) so as it is possible to request it (*obj.output*) at any time. Note that the default value for *stroreOutput* is *True*, so it is not necessary to provide it in the parameters.
100
101 .. code-block:: python
102
103 import time
104 import sys
105 from mozprocess import processhandler
106
107 command = './proc_sleep_echo.sh' # Windows: 'proc_sleep_echo.bat'
108
109 p = processhandler.ProcessHandler(command, storeOutput=True)
110 p.run()
111 for i in xrange(10):
112 print(p.output)
113 time.sleep(0.5)
114 p.wait()
115
116 In previous example, you will see the *p.output* list growing.
117
118 Execution
119 ---------
120
121 Status
122 ``````
123
124 It is possible to query the status of the process via *poll()* that will return None if the process is still running, 0 if it ended without failures and a negative value if it was killed by a signal (Unix-only).
125
126 .. code-block:: python
127
128 import time
129 import signal
130 from mozprocess import processhandler
131
132 command = './proc_sleep_echo.sh'
133 p = processhandler.ProcessHandler(command)
134 p.run()
135 time.sleep(2)
136 print("poll status: %s" % p.poll())
137 time.sleep(1)
138 p.kill(signal.SIGKILL)
139 print("poll status: %s" % p.poll())
140
141 Timeout
142 ```````
143
144 A timeout can be provided to the *run()* method. If the process last more than timeout seconds, it will be stopped.
145
146 After execution, the property *timedOut* will be set to True if a timeout was reached.
147
148 It is also possible to provide functions (*obj = ProcessHandler[Mixin](..., onTimeout=functions)*) that will be called if the timeout was reached.
149
150 .. code-block:: python
151
152 from mozprocess import processhandler
153
154 def ontimeout():
155 print("REACHED TIMEOUT")
156
157 command = './proc_sleep_echo.sh' # Windows: 'proc_sleep_echo.bat'
158 functions = [ontimeout]
159 p = processhandler.ProcessHandler(command, onTimeout=functions)
160 p.run(timeout=2)
161 p.wait()
162 print("timedOut = %s" % p.timedOut)
163
164 By default the process will be killed on timeout but it is possible to prevent this by setting *kill_on_timeout* to *False*.
165
166 .. code-block:: python
167
168 p = processhandler.ProcessHandler(command, onTimeout=functions, kill_on_timeout=False)
169 p.run(timeout=2)
170 p.wait()
171 print("timedOut = %s" % p.timedOut)
172
173 In this case, no output will be available after the timeout, but the process will still be running.
174
175 Waiting
176 ```````
177
178 It is possible to wait until the process exits as already seen with the method *wait()*, or until the end of a timeout if given. Note that in last case the process is still alive after the timeout.
179
180 .. code-block:: python
181
182 command = './proc_sleep_echo.sh' # Windows: 'proc_sleep_echo.bat'
183 p = processhandler.ProcessHandler(command)
184 p.run()
185 p.wait(timeout=2)
186 print("timedOut = %s" % p.timedOut)
187 p.wait()
188
189 Killing
190 ```````
191
192 You can request to kill the process with the method *kill*. f the parameter "ignore_children" is set to False when the process handler class is initialized, all the process's children will be killed as well.
193
194 Except on Windows, you can specify the signal with which to kill method the process (e.g.: *kill(signal.SIGKILL)*).
195
196 .. code-block:: python
197
198 import time
199 from mozprocess import processhandler
200
201 command = './proc_sleep_echo.sh' # Windows: 'proc_sleep_echo.bat'
202 p = processhandler.ProcessHandler(command)
203 p.run()
204 time.sleep(2)
205 p.kill()
206
207 End of execution
208 ````````````````
209
210 You can provide a function or a list of functions to call at the end of the process using the initilization parameter *onFinish*.
211
212 .. code-block:: python
213
214 from mozprocess import processhandler
215
216 def finish():
217 print("Finished!!")
218
219 command = './proc_sleep_echo.sh' # Windows: 'proc_sleep_echo.bat'
220
221 p = processhandler.ProcessHandler(command, onFinish=finish)
222 p.run()
223 p.wait()
224
225 Child management
226 ----------------
227
228 Consider the following scripts:
229
230 **proc_child.sh**:
231
232 .. code-block:: sh
233
234 #!/bin/sh
235 for i in a b c d e
236 do
237 echo $i
238 sleep 1
239 done
240
241 **proc_parent.sh**:
242
243 .. code-block:: sh
244
245 #!/bin/sh
246 ./proc_child.sh
247 for i in 1 2 3 4 5
248 do
249 echo $i
250 sleep 1
251 done
252
253 For windows users consider:
254
255 **proc_child.bat**:
256
257 .. code-block:: bat
258
259 @echo off
260 FOR %%A IN (a b c d e) DO (
261 ECHO %%A
262 REM TIMEOUT /T 1 /NOBREAK
263 PING -n 2 127.0.0.1 > NUL
264 )
265
266 **proc_parent.bat**:
267
268 .. code-block:: bat
269
270 @echo off
271 call proc_child.bat
272 FOR %%A IN (1 2 3 4 5) DO (
273 ECHO %%A
274 REM TIMEOUT /T 1 /NOBREAK
275 PING -n 2 127.0.0.1 > NUL
276 )
277
278 For processes that launch other processes, mozprocess allows you to get child running status, wait for child termination, and kill children.
279
280 Ignoring children
281 `````````````````
282
283 By default the *ignore_children* option is False. In that case, killing the main process will kill all its children at the same time.
284
285 .. code-block:: python
286
287 import time
288 from mozprocess import processhandler
289
290 def finish():
291 print("Finished")
292
293 command = './proc_parent.sh'
294 p = processhandler.ProcessHandler(command, ignore_children=False, onFinish=finish)
295 p.run()
296 time.sleep(2)
297 print("kill")
298 p.kill()
299
300 If *ignore_children* is set to *True*, killing will apply only to the main process that will wait children end of execution before stoping (join).
301
302 .. code-block:: python
303
304 import time
305 from mozprocess import processhandler
306
307 def finish():
308 print("Finished")
309
310 command = './proc_parent.sh'
311 p = processhandler.ProcessHandler(command, ignore_children=True, onFinish=finish)
312 p.run()
313 time.sleep(2)
314 print("kill")
315 p.kill()
316
317 API Documentation
318 -----------------
319
320 .. module:: mozprocess
321 .. autoclass:: ProcessHandlerMixin
322 :members: __init__, timedOut, commandline, run, kill, processOutputLine, onTimeout, onFinish, wait
323 .. autoclass:: ProcessHandler
324 :members:

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