stdin

stdin

[JJK]

Hello there list,

Apologies if this is not the correct place to post this question, if
you could let me know where is, I shall attempt there.

I am using gdb on a program that uses fgets to read from stdin.

after launching "gdb program", how may I invoke the program as if I
was actually executing "echo wibble | program".

thank you for any help you can give me,

James

Re: stdin

[Joel Brobecker]

> after launching "gdb program", how may I invoke the program as if I
> was actually executing "echo wibble | program".

Not tested, but would you be able to put the text you want to pipe
into a file, and then do "run < your_file"?

-- 
Joel

Re: stdin

[Michael Veksler]

Joel Brobecker wrote:
>> after launching "gdb program", how may I invoke the program as if I
>> was actually executing "echo wibble | program".
>>     
>
> Not tested, but would you be able to put the text you want to pipe
> into a file, and then do "run < your_file"?
>
>   
That will work only if

   1. your_file is small enough. I sometimes pipe GBs of data through pipes.
   2. You don't mind that the behavior of pipes and files is different
      in some cases. The bug that you hunt might go away due to this
      difference (like it might disappear by changing an unrelated
      environment variable - yes I have seen such bugs).
      Also, a program such as 'less' might behave differently, on
      purpose, when reading from a pipe and not a file.

Another solution:
in (T)CSH: setenv SHELL /bin/zsh
or in (BA)SH: export SHELL=/bin/zsh
Then:
=> gdb /bin/cat
....
(gdb) r < <(echo ok)
ok

What happens here is that <(some command) means that the command is run, 
its output is written to a pipe. The pipe gets a name (named pipe or 
through /dev/fd/[0-9]), and that name is used in
(gdb) r < the_name_of_the_pipe

Actual implementation may be different (because '<' does not require a 
name), but the main idea remains. Anyway, this is a work-around, not a 
true solution.

Michael