I'm calling a library function that prsnts something to stdout.

Long story but I can't change this function for now, too much ripple.

I need to
1. open a pipe to capture stdout.
2. save to string.
3. return string
4. close pipe.


Ony thing I have is:

bool ExCommand(string& cmd,vector<string>& ret)
{
string s;
static  char      buf[BUFSZ];
FILE    *ptr      = NULL;

if (cmd.empty()) return false;

if ((ptr = popen(cmd.c_str(), "r")) NE NULL)
{
while (fgets(buf, BUFSZ, ptr) NE NULL)
{
buf[strlen(buf)-1] = '\0';
s = buf;
ret.push_back(s);
}
pclose(ptr);
}
else
{
return false;
}
return true;
}


But this executes an extern shell command.  I'm calling a function
inside a library.



--
___  _ ____       ___       __  __
/ _ )(_) / /_ __  / _ \___ _/ /_/ /____  ___
/ _  / / / / // / / ___/ _ `/ __/ __/ _ \/ _ \
/____/_/_/_/\_, / /_/   \_,_/\__/\__/\___/_//_/
/___/
Texas Instruments ASIC Circuit Design Methodlogy Group
Dallas, Texas, 214-480-4455,  b-patton@ti.com

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Billy N. Patton wrote:
> I'm calling a library function that prsnts something to stdout.
>
> Long story but I can't change this function for now, too much ripple.
>
> I need to
> 1. open a pipe to capture stdout.
> 2. save to string.
> 3. return string
> 4. close pipe.
[snip]

That seems a bit difficult to do with pipes.

Have you considered an alternative, like using freopen(3) to capture stdout 
to a
file, then reading the file?


- --
Lew Pitcher
IT Consultant, Enterprise Data Systems,
Enterprise Technology Solutions, TD Bank Financial Group

(Opinions expressed are my own, not my employers')
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Lew Pitcher wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> Billy N. Patton wrote:
> 
>
> [snip]
>
> That seems a bit difficult to do with pipes.
>
> Have you considered an alternative, like using freopen(3) to capture stdou
t to a
> file, then reading the file?

Yes but don't want to do that much IO.
Besides I may have 100's running in batch around the network.
Bookkeeping could get nasty for unique file names.

>
>
> - --
> Lew Pitcher
> IT Consultant, Enterprise Data Systems,
> Enterprise Technology Solutions, TD Bank Financial Group
>
> (Opinions expressed are my own, not my employers')
> -----BEGIN PGP SIGNATURE-----
> Version: GnuPG v1.2.4 (MingW32)
>
>  iD8DBQFBdAkIagVFX4UWr64RAvW5AKCSEnhAc7ed
47uWucul8RhteB+nlwCfVsTK
> fNJVXzwNbB/OD8p5M8vL3S4=
> =54+A
> -----END PGP SIGNATURE-----


--
___  _ ____       ___       __  __
/ _ )(_) / /_ __  / _ \___ _/ /_/ /____  ___
/ _  / / / / // / / ___/ _ `/ __/ __/ _ \/ _ \
/____/_/_/_/\_, / /_/   \_,_/\__/\__/\___/_//_/
/___/
Texas Instruments ASIC Circuit Design Methodlogy Group
Dallas, Texas, 214-480-4455,  b-patton@ti.com

[ Post a follow-up to this message ]

In article <cl101j$h4g$1@home.itg.ti.com>,
"Billy N. Patton" <b-patton@ti.com> wrote:

> I'm calling a library function that prsnts something to stdout.
>
> Long story but I can't change this function for now, too much ripple.
>
> I need to
> 1. open a pipe to capture stdout.
> 2. save to string.
> 3. return string
> 4. close pipe.
...

> But this executes an extern shell command.  I'm calling a function
> inside a library.

What you could do is something like the following pseudocode:

dup(saved_stdout, STDOUT_FILENO);
pipe(pipefd);
dup2(STDOUT_FILENO, pipefd[1]);
close(pipefd[1]);
create a thread that reads from pipefd[0] and accumulates it into a
string
call the function
dup2(STDOUT_FILENO, saved_stdout);
The thread should now exit when it reads EOF from the pipe
close(pipefd[0])
Process the string

--
Barry Margolin, barmar@alum.mit.edu
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***

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