[Crash-utility] [PATCH] cmdline: allow to specify a script directly in pipeline

[Kazuhito Hagio]

On 9/27/2018 1:42 PM, Dave Anderson wrote:
> 
> 
> ----- Original Message -----
>> Currently, when using pipe in command line, we cannot specify
>> a script with shebang directly like this:
>>
>>   crash> foreach bt | ./analyze.awk
>>   crash: pipe operation failed
>>
>>   (or it looks like crash can loop until Ctrl-C depending on timing)
>>
>> This is a bit confusing and inconvenient because it's not shell-like
>> behavior.
>>
>> The cause is that output_command_to_pids() searches /proc/PID/stat
>> files for "(path/to/script)" string and cannot find such process,
>> and also the ps kludge doesn't work well in this case.  This patch
>> removes the part except its file name like "(script)" so that it can
>> find the process.
> 
> Just to clarify, is this is due to using "./analyze.awk" (with the preceding "./"),
> whereas if you were to use "analyze.awk", it would work OK?

No, it doesn't because "sh -c analyze.awk" does not work.
This behavior will not change with this patch, and I think
it should not change.

[before]
  crash> bt | awk -f analyze.awk
  analyzed
  crash> bt | ./analyze.awk
  crash: pipe operation failed
  crash> bt | analyze.awk
  sh: analyze.awk: command not found
  crash: pipe operation failed

[after]
  crash> bt | awk -f analyze.awk
  analyzed
  crash> bt | ./analyze.awk
  analyzed
  crash> bt | analyze.awk
  sh: analyze.awk: command not found
  crash: pipe operation failed

Thanks,
Kazu

> 
> Dave
> 
> 
>>
>> Signed-off-by: Kazuhito Hagio <k-hagio at ab.jp.nec.com>
>> ---
>>  cmdline.c | 5 +++--
>>  1 file changed, 3 insertions(+), 2 deletions(-)
>>
>> diff --git a/cmdline.c b/cmdline.c
>> index ee08f06..c0a9f4f 100644
>> --- a/cmdline.c
>> +++ b/cmdline.c
>> @@ -806,7 +806,7 @@ output_command_to_pids(void)
>>          char buf1[BUFSIZE];
>>          char buf2[BUFSIZE];
>>          char lookfor[BUFSIZE+2];
>> -        char *pid, *name, *status, *p_pid, *pgrp;
>> +        char *pid, *name, *status, *p_pid, *pgrp, *comm;
>>  	char *arglist[MAXARGS];
>>  	int argc;
>>  	FILE *pipe;
>> @@ -815,7 +815,8 @@ output_command_to_pids(void)
>>  	retries = 0;
>>  	shell_has_exited = FALSE;
>>  	pc->pipe_pid = pc->pipe_shell_pid = 0;
>> -        sprintf(lookfor, "(%s)", pc->pipe_command);
>> +	comm = strrchr(pc->pipe_command, '/');
>> +	sprintf(lookfor, "(%s)", comm ? ++comm : pc->pipe_command);
>>  	stall(1000);
>>  retry:
>>          if (is_directory("/proc") && (dirp = opendir("/proc"))) {
>> --
>> 1.8.3.1
>>
>> --
>> Crash-utility mailing list
>> Crash-utility at redhat.com
>> https://www.redhat.com/mailman/listinfo/crash-utility
>>
> 
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