[CRIU] [PATCH 1/2] test: replace cat in Makefiles with awk

[Vitaly Ostrosablin]

>2017-01-12 11:20 GMT+03:00 Dmitry Safonov <0x7f454c46 at gmail.com>:
>> 2017-01-12 9:27 GMT+03:00 Vitaly Ostrosablin <vostrosablin at virtuozzo.com>:
>>> cat *.pid works when we have only one running process at any moment.
>>> That's because pidfiles contain no newlines and cat will just
>>> concatenate content of all files present in directory. So, e.g., if we
>>> have pidfiles:
>>>
>>> 31338
>>> 31359
>>> 31880
>>> 31884
>>> 31889
>>>
>>> cat will build following string from those pidfiles:
>>>
>>> 3133831359318803188431889
>>
>> I don't mind the patch, but your explanation looks obiviously wrong:
>> [test]$ echo 123 > 1.txt
>> [test]$ echo 456 > 2.txt
>> [test]$ cat *.txt
>> 123
>> 456
>> [test]$ cat Makefile
>> all:
>>     cat *.txt
>> [test]$ make
>> cat *.txt
>> 123
>> 456
>
>[test]$ cat Makefile
>all:
>    echo `cat *.txt`
>[test]$ make
>echo `cat *.txt`
>123 456
>[test]$
>


It doesn't look really wrong. What cat does is just a concatenation

of files content and doesn't modify it in any way. What you put into

files is what you get. So, concatenating '123\n' and '456\n' gives


123

456


Now let's do same with concatenation of '123' and '456'. The result

is clearly:


123456


cat doesn't append it's own newlines. Now let's use echo with no-newline

option:


 echo -n 123 > 1.txt
 echo -n 456 > 2.txt
 cat *.txt
123456%

(Percent sign at end in zsh means that output ended without newline being
printed.)

Here's how we write the pidfile in zdtm lib/test.c:

if (dprintf(fd, "%d", pid) == -1) {
fprintf(stderr, "Can't write in the file %s: %m\n", tmp);
goto err_c;
}

It just prints %d, i.e. pid only, without newline at end. So, if we were to cat
all pidfiles, we'll just get a single huge undelimited number.

>>
>> Is it something that depends on environment, like ${IFS} in bash?
>> Check, please.
>>
>>>
>>> Obviously, kill would fail to send signals to processes, because it's
>>> now a single big number, which cannot be unambigously split back in
>>> general case.
>>>
>>> That's where awk comes in. We don't need to modify C part of tests to
>>> print newlines at end of file. We just order awk to print content of
>>> each file, which adds a newline at end - problem solved, kill can once
>>> again parse, which PIDs it get and send proper signals to them. Also,
>>> should be completely safe for zdtm.py, because it doesn't use Makefiles
>>> and sends signals on it's own.
>>> ---
>>>  test/zdtm/static/Makefile     | 4 ++--
>>>  test/zdtm/transition/Makefile | 4 ++--
>>>  2 files changed, 4 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/test/zdtm/static/Makefile b/test/zdtm/static/Makefile
>>> index af1254f5..8fe9d953 100644
>>> --- a/test/zdtm/static/Makefile
>>> +++ b/test/zdtm/static/Makefile
>>> @@ -338,7 +338,7 @@ start:      $(PID) $(STATE)
>>>  check_start:   $(PID:%.pid=%.is_running)
>>>
>>>  stop:  $(STATE_OUT)
>>> -       -kill -TERM `cat *.pid`
>>> +       -kill -TERM `awk '{print}' *.pid`
>>>
>>>  WAIT_TIME=240
>>>  %.stop:        %.pid %
>>> @@ -356,7 +356,7 @@ WAIT_TIME=240
>>>  wait_stop:
>>>                 i=0; >>                 while [ $$i -lt $(WAIT_TIME) ] ; do >> -               kill -0 `cat *.pid 2>/dev/null` 2>
/dev/null || break; >> +               kill -0 `awk '{print}' *.pid 2>/dev/null` 2>/dev/null || break; >>                 sleep 1; >>
                i=`expr $$i + 1`; >>         done
>>> diff --git a/test/zdtm/transition/Makefile b/test/zdtm/transition/Makefile
>>> index 7ddb2384..dfc10ef5 100644
>>> --- a/test/zdtm/transition/Makefile
>>> +++ b/test/zdtm/transition/Makefile
>>> @@ -65,12 +65,12 @@ start:      $(PID)
>>>  check_start:   $(PID:%.pid=%.is_running)
>>>
>>>  stop:
>>> -       -kill -TERM `cat *.pid`
>>> +       -kill -TERM `awk '{print}' *.pid`
>>>
>>>  WAIT_TIME=10
>>>  wait_stop:
>>>         -for i in `seq 1 $(WAIT_TIME)`; do >> -               kill -0 `cat *.pid 2>/dev/null` 2>/dev/null || break; >> +
     kill -0 `awk '{print}' *.pid 2>/dev/null` 2>/dev/null || break; >>                 sleep 1; >>         done
>>>
>>> --
>>> 2.11.0
>>>
>>> _______________________________________________
>>> CRIU mailing list
>>> CRIU at openvz.org
>>> https://lists.openvz.org/mailman/listinfo/criu
>
>>
>>
>>
>> --
>>              Dmitry
>
>
>
>--
>             Dmitry


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