Very Computer

      flags = fcntl(fileno(stdin),F_GETFD);
      flags &= !FD_CLOEXEC;
      fcntl(fileno(stdin),F_SETFD,flags);

      flags = fcntl(fileno(stdout),F_GETFD);
      flags &= !FD_CLOEXEC;
      fcntl(fileno(stdout),F_SETFD,flags);

      if (execlp(DECOMPRESSOR,DECOMPRESSOR,"-d",NULL))
        perror("execlp");

but although compress is launched successfully, it complains about
unexpected end of input.  strace shows the first read() returning
zero.  What did I miss?

(The kernel is Linux 2.2.17, libc is GNU libc 2.2.3 .)

--

Make a good day.

 Mark> I need to run *part* of standard input through compress, after
 Mark> inspecting the remainder.  (It's for a weird newsfeed -- boring
 Mark> details on request.)  While I could pipe it through a
 Mark> subprocess, that's a rather complicated dance, and I thought
 Mark> there ought to be a way to pass the properly-positioned file
 Mark> descriptor to compress.  It sure *looks* as though I should be
 Mark> able to do something like this:

 Mark>       flags = fcntl(fileno(stdin),F_GETFD);
 Mark>       flags &= !FD_CLOEXEC;
 Mark>       fcntl(fileno(stdin),F_SETFD,flags);

 Mark>       flags = fcntl(fileno(stdout),F_GETFD);
 Mark>       flags &= !FD_CLOEXEC;
 Mark>       fcntl(fileno(stdout),F_SETFD,flags);

you shouldn't need to do any of that. FD_CLOEXEC will not be set on
stdin or stdout (unless your program did so itself, which is
perverse).

However, if you've used any of the stdio functions to read from stdin,
then it will almost certainly be positioned incorrectly for your
purposes. (The stdio functions will read more data than expected.)  If
stdin is a pipe (and therefore not seekable), then you'll basically
have to avoid using any stdio functions on it at all; if it's a plain
file, then you should call lseek (not fseek) before the exec to get
the positioning correct.

--
Andrew.

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Quote:> However, if you've used any of the stdio functions to read from stdin,
> then it will almost certainly be positioned incorrectly for your
> purposes. (The stdio functions will read more data than expected.)

--

Make a good day.