| PROC_INITSTDIO(3PROC) | Process Control Library Functions | PROC_INITSTDIO(3PROC) |
proc_initstdio,
proc_flushstdio,
proc_finistdio — stdio
buffering functions
Process Control Library (libproc, -lproc)
#include
<libproc.h>
int
proc_initstdio(void);
int
proc_flushstdio(void);
int
proc_finistdio(void);
The
proc_initstdio(),
proc_flushstdio(), and
proc_finistdio() functions are utilities provided to
aid with the possibility of deadlock while doing I/O operations. If a
process is trying to do I/O, but holding the process handle that would
consume that I/O, then eventually the program holding the process handle
will block as none of its I/O has been drained. However, because it is
holding a process handle to that process, it will never be drained.
Consider, for example, the following invocation:
pfiles `pgrep xterm` where the command was launched
from a shell on an xterm. Because the xterm is stopped, it will not be able
to write out any of the standard out that gets passed to it, leading to a
deadlock. The pfiles program cannot release the
xterm process because it still has pending I/O, but
the I/O cannot be drained due to the same hold.
To address this, these functions duplicate the standard output and standard error of the process to temporary files and then flushes it out to the original file descriptors and streams later. When finished, the original file descriptors are restored as standard out and standard error.
The
proc_initstdio()
function initializes a new standard out and standard error file descriptors
and retains the originals.
The
proc_flushstdio()
functions flushes all of the cached data from the temporary standard out and
standard error back to the underlying ones. This function should only be
called after all process handles have been released. For example, if
iterating on multiple processes, calling this after handling each one is
safe.
The
proc_finistdio()
flushes any outstanding I/O and restores the original standard output and
standard error.
Once called, the
proc_initstdio()
function must not be called again until a successful call to
proc_finistdio().
Upon successful completion, the
proc_initstdio(),
proc_flushstdio(), and
proc_finistdio() functions all return
0. Otherwise,
-1 is returned
to indicate failure.
| November 27, 2023 | OmniOS |