10-07-2011
Are you checking for builtins
after you fork?
You should check
before. The whole point is that builtins don't need fork at all since they can happen wholly inside the shell.
I don't understand why you'd be using builtins in the middle of a pipe chain in the first place. They don't work there in csh. Unless you're trying to build in things like
cat, which I don't think is a good idea.
Of course external commands must exist to use external commands. What's wrong with that?
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LEARN ABOUT DEBIAN
filter_create_fd
filter_create_fd(3) util/filter.h filter_create_fd(3)
NAME
filter_create_fd - Create a sub process and return the requested pipes
SYNOPSIS
#include <util/filter.h>
NEOERR *filter_create_fd(const char *cmd, int *fdin, int *fdout, int *fderr,
pid_t *pid);
ARGUMENTS
cmd -> the sub command to execute. Will be executed with
/bin/sh -c
fdin -> pointer to return the stdin pipe, or NULL if you don't
want the stdin pipe
fdout -> pointer to return the stdout pipe, or NULL if you don't
want the stdout pipe
fderr -> pointer to return the stderr pipe, or NULL if you don't
want the stderr pipe
DESCRIPTION
filter_create_fd and filter_create_fp are what popen
been: a mechanism to create sub processes and have pipes to all their input/output. The concept was taken from mutt, though python has
something similar with popen3/popen4. You control which pipes the function returns by the fdin/fdout/fderr arguments. A NULL value means
"don't create a pipe", a pointer to an int will cause the pipes to be created and the value of the file descriptor stored in the int. You
will have to close(2) the file descriptors yourself.
RETURN VALUE
fdin -> the stdin file descriptor of the sub process
fdout -> the stdout file descriptor of the sub process
fderr -> the stderr file descriptor of the sub process
pid -> the pid of the sub process
SEE ALSO
filter_wait(3), filter_create_fp(3), filter_create_fd
ClearSilver 12 July 2007 filter_create_fd(3)