|
Bob Selby(deleted)
|
Restoring STDIN after redirection on command line ...
|
|
Bob Selby(deleted)
05/02/2012 4:46 AM
post92871
|
Restoring STDIN after redirection on command line ...
A bit of a newbie question, possibly.
I am trying to have a QNX 650 built utility that normally accepts its input from stdin but can be run with a script file
with "utility < scriptfile" and then revert to input from the keyboard when it hits EOF.
What is the best way to do this ??
Currently, at EOF I close "stdin" and then fopen("/dev/tty", "r") - this works well for the debug serial port but not
for telnet, etc.
TIA,
Bob
|
|
|
|
|
|
Thomas Haupt
|
RE: Restoring STDIN after redirection on command line ...
|
|
Thomas Haupt
05/02/2012 6:26 AM
post92875
|
RE: Restoring STDIN after redirection on command line ...
Hi Bob,
I'm not sure if there is a really clean solution to your problem.
To achieve the desired behavior, you would need to:
- find out which device should become your new stdin
(as you noticed, /dev/tty isn't necessarily the right choice), and
- redirect the stream 'stdin' to take its input from that device.
Finding the appropriate device may be anywhere between not too hard
and impossible. In the easy case, stdout or stderr refer to the TTY
you want to use. In the worst case, they have been redirected to
files or closed entirely, and your process has detached from its
controlling terminal (i.e., become a daemon) - in this scenario,
there'd be no reasonable guess which device to attach to.
Let's assume a simple case - stdout refers to a TTY.
You could of course just call dup2( 1, 0 ) to duplicate the
stdout file descriptor and have the duplicate your current stdin
fd. The problem is that the (FILE) stream object represented by
*stdin will not be aware of this change. There is the fdopen()
function to wrap a FILE object around an existing file descriptor,
but that will allocate a new object, not use an existing one...
...and alas, *stdin/-out/-err are static _objects_ - so we cannot
merely replace stdin by a new pointer.
You could try to flush and rewind the stdin stream, then
call dup2( 1, 0 ) to replace the stdin file descriptor.
I'd suggest, though, to provide your input file via a command line
argument and have a few custom input functions that will read either
from that file or, once it reached EOF, the original stdin.
Cheers,
Thomas
-----Original Message-----
From: Bob Selby [mailto:robert.selby@snellgroup.com]
Sent: Mittwoch, 2. Mai 2012 10:46
To: ostech-core_os
Subject: Restoring STDIN after redirection on command line ...
A bit of a newbie question, possibly.
I am trying to have a QNX 650 built utility that normally accepts its input from stdin but can be run with a script file
with "utility < scriptfile" and then revert to input from the keyboard when it hits EOF.
What is the best way to do this ??
Currently, at EOF I close "stdin" and then fopen("/dev/tty", "r") - this works well for the debug serial port but not
for telnet, etc.
TIA,
Bob
_______________________________________________
OSTech
http://community.qnx.com/sf/go/post92871
To cancel your subscription to this discussion, please e-mail ostech-core_os-unsubscribe@community.qnx.com
|
|
|
|
|
|
Bob Selby(deleted)
|
RE: Restoring STDIN after redirection on command line ...
|
|
Bob Selby(deleted)
05/02/2012 7:15 AM
post92877
|
RE: Restoring STDIN after redirection on command line ...
Thanks for that :-)
I tried the following for "util < scriptfile" and it seems to do what I
want ...
-----------------------------------------------------
FILE * fc = stdin;
...
fgets(fc, ... // Reads from redirected script file
...
On EOF I do ...
fclose(fc);
fc = fdopen(STDOUT_FILENO, "r") ) == NULL )
...
fgets(fc, ... // Reads from keyboard
...
-----------------------------------------------------
Bob Selby
Senior Engineer, Software
Snell
Innovation in the
Multi-Screen World
T +44 (0) 118 921 4592 (direct)
T +44 (0) 118 986 6123 (switchboard)
F +44 (0) 118 975 4920
snellgroup.com
Hartman House, Danehill, Lower Earley, Reading, Berkshire, RG6 4PB UK
Routing | Modular Infrastructure | Conversion & Restoration | Live
Production | Automation & Media Management | Control & Monitoring
-----Original Message-----
From: Thomas Haupt [mailto:thaupt@qnx.com]
Sent: 02 May 2012 11:24
To: 'ostech-core_os@community.qnx.com'
Subject: RE: Restoring STDIN after redirection on command line ...
Hi Bob,
I'm not sure if there is a really clean solution to your problem.
To achieve the desired behavior, you would need to:
- find out which device should become your new stdin
(as you noticed, /dev/tty isn't necessarily the right choice), and
- redirect the stream 'stdin' to take its input from that device.
Finding the appropriate device may be anywhere between not too hard and
impossible. In the easy case, stdout or stderr refer to the TTY you want
to use. In the worst case, they have been redirected to files or closed
entirely, and your process has detached from its controlling terminal
(i.e., become a daemon) - in this scenario, there'd be no reasonable
guess which device to attach to.
Let's assume a simple case - stdout refers to a TTY.
You could of course just call dup2( 1, 0 ) to duplicate the stdout
file descriptor and have the duplicate your current stdin fd. The
problem is that the (FILE) stream object represented by *stdin will not
be aware of this change. There is the fdopen() function to wrap a FILE
object around an existing file descriptor, but that will allocate a new
object, not use an existing one...
...and alas, *stdin/-out/-err are static _objects_ - so we cannot merely
replace stdin by a new pointer.
You could try to flush and rewind the stdin stream, then call dup2( 1,
0 ) to replace the stdin file descriptor.
I'd suggest, though, to provide your input file via a command line
argument and have a few custom input functions that will read either
from that file or, once it reached EOF, the original stdin.
Cheers,
Thomas
-----Original Message-----
From: Bob Selby [mailto:robert.selby@snellgroup.com]
Sent: Mittwoch, 2. Mai 2012 10:46
To: ostech-core_os
Subject: Restoring STDIN after redirection on command line ...
A bit of a newbie question, possibly.
I am trying to have a QNX 650 built utility that normally accepts its
input from stdin but can be run with a script file with "utility <
scriptfile" and then revert to input from the keyboard when it hits EOF.
What is the best way to do this ??
Currently, at EOF I close "stdin" and then fopen("/dev/tty", "r") - this
works well for the debug serial port but not for telnet, etc.
TIA,
Bob
_______________________________________________
OSTech
http://community.qnx.com/sf/go/post92871
To cancel your subscription to this discussion, please e-mail
ostech-core_os-unsubscribe@community.qnx.com
_______________________________________________
OSTech
http://community.qnx.com/sf/go/post92875
To cancel your subscription to this discussion, please e-mail
ostech-core_os-unsubscribe@community.qnx.com
This email and any attachments are confidential, may be legally privileged and are intended for the use of the addressee
only. If you are not the intended recipient, please note that any use, disclosure, printing or copying of...
View Full Message
|
|
|
|
|
|
Thomas Haupt
|
RE: Restoring STDIN after redirection on command line ...
|
|
Thomas Haupt
05/02/2012 7:31 AM
post92878
|
RE: Restoring STDIN after redirection on command line ...
Hi Bob,
that looks mostly reasonable. I'd still add a 'dup' or 'dup2',
though, to have separate file descriptors for stdin and stdout.
Cheers,
Thomas
-----Original Message-----
From: Robert Selby [mailto:Robert.Selby@snellgroup.com]
Sent: Mittwoch, 2. Mai 2012 13:12
To: ostech-core_os@community.qnx.com
Subject: RE: Restoring STDIN after redirection on command line ...
Thanks for that :-)
I tried the following for "util < scriptfile" and it seems to do what I want ...
-----------------------------------------------------
FILE * fc = stdin;
...
fgets(fc, ... // Reads from redirected script file ...
On EOF I do ...
fclose(fc);
fc = fdopen(STDOUT_FILENO, "r") ) == NULL ) ...
fgets(fc, ... // Reads from keyboard
...
-----------------------------------------------------
Bob Selby
Senior Engineer, Software
Snell
Innovation in the
Multi-Screen World
T +44 (0) 118 921 4592 (direct)
T +44 (0) 118 986 6123 (switchboard)
F +44 (0) 118 975 4920
snellgroup.com
Hartman House, Danehill, Lower Earley, Reading, Berkshire, RG6 4PB UK
Routing | Modular Infrastructure | Conversion & Restoration | Live Production | Automation & Media Management | Control & Monitoring
-----Original Message-----
From: Thomas Haupt [mailto:thaupt@qnx.com]
Sent: 02 May 2012 11:24
To: 'ostech-core_os@community.qnx.com'
Subject: RE: Restoring STDIN after redirection on command line ...
Hi Bob,
I'm not sure if there is a really clean solution to your problem.
To achieve the desired behavior, you would need to:
- find out which device should become your new stdin
(as you noticed, /dev/tty isn't necessarily the right choice), and
- redirect the stream 'stdin' to take its input from that device.
Finding the appropriate device may be anywhere between not too hard and impossible. In the easy case, stdout or stderr refer to the TTY you want to use. In the worst case, they have been redirected to files or closed entirely, and your process has detached from its controlling terminal (i.e., become a daemon) - in this scenario, there'd be no reasonable guess which device to attach to.
Let's assume a simple case - stdout refers to a TTY.
You could of course just call dup2( 1, 0 ) to duplicate the stdout file descriptor and have the duplicate your current stdin fd. The problem is that the (FILE) stream object represented by *stdin will not be aware of this change. There is the fdopen() function to wrap a FILE object around an existing file descriptor, but that will allocate a new object, not use an existing one...
...and alas, *stdin/-out/-err are static _objects_ - so we cannot merely replace stdin by a new pointer.
You could try to flush and rewind the stdin stream, then call dup2( 1,
0 ) to replace the stdin file descriptor.
I'd suggest, though, to provide your input file via a command line argument and have a few custom input functions that will read either from that file or, once it reached EOF, the original stdin.
Cheers,
Thomas
-----Original Message-----
From: Bob Selby [mailto:robert.selby@snellgroup.com]
Sent: Mittwoch, 2. Mai 2012 10:46
To: ostech-core_os
Subject: Restoring STDIN after redirection on command line ...
A bit of a newbie question, possibly.
I am trying to have a QNX 650 built utility that normally accepts its input from stdin but can be run with a script file with "utility < scriptfile" and then revert to input from the keyboard when it hits EOF.
What is the best way to do this ??
Currently, at EOF I close "stdin" and then fopen("/dev/tty", "r") - this works well for the debug serial port but not
for telnet, etc.
TIA,
Bob
_______________________________________________
OSTech
http://community.qnx.com/sf/go/post92871
To cancel your subscription to this discussion, please e-mail...
View Full Message
|
|
|
|
|
|
Bob Selby(deleted)
|
RE: Restoring STDIN after redirection on command line ...
|
|
Bob Selby(deleted)
05/02/2012 7:37 AM
post92879
|
RE: Restoring STDIN after redirection on command line ...
Very true ...
fc = fdopen(dup2(1, 0), "r");
seems to work OK too :-)
Thanks very much for the help :-)
Bob Selby
Senior Engineer, Software
Snell
Innovation in the
Multi-Screen World
T +44 (0) 118 921 4592 (direct)
T +44 (0) 118 986 6123 (switchboard)
F +44 (0) 118 975 4920
snellgroup.com
Hartman House, Danehill, Lower Earley, Reading, Berkshire, RG6 4PB UK
Routing | Modular Infrastructure | Conversion & Restoration | Live
Production | Automation & Media Management | Control & Monitoring
-----Original Message-----
From: Thomas Haupt [mailto:thaupt@qnx.com]
Sent: 02 May 2012 12:29
To: 'ostech-core_os@community.qnx.com'
Subject: RE: Restoring STDIN after redirection on command line ...
Hi Bob,
that looks mostly reasonable. I'd still add a 'dup' or 'dup2', though,
to have separate file descriptors for stdin and stdout.
Cheers,
Thomas
-----Original Message-----
From: Robert Selby [mailto:Robert.Selby@snellgroup.com]
Sent: Mittwoch, 2. Mai 2012 13:12
To: ostech-core_os@community.qnx.com
Subject: RE: Restoring STDIN after redirection on command line ...
Thanks for that :-)
I tried the following for "util < scriptfile" and it seems to do what I
want ...
-----------------------------------------------------
FILE * fc = stdin;
...
fgets(fc, ... // Reads from redirected script file ...
On EOF I do ...
fclose(fc);
fc = fdopen(STDOUT_FILENO, "r") ) == NULL ) ...
fgets(fc, ... // Reads from keyboard
...
-----------------------------------------------------
Bob Selby
Senior Engineer, Software
Snell
Innovation in the
Multi-Screen World
T +44 (0) 118 921 4592 (direct)
T +44 (0) 118 986 6123 (switchboard)
F +44 (0) 118 975 4920
snellgroup.com
Hartman House, Danehill, Lower Earley, Reading, Berkshire, RG6 4PB UK
Routing | Modular Infrastructure | Conversion & Restoration | Live
Production | Automation & Media Management | Control & Monitoring
-----Original Message-----
From: Thomas Haupt [mailto:thaupt@qnx.com]
Sent: 02 May 2012 11:24
To: 'ostech-core_os@community.qnx.com'
Subject: RE: Restoring STDIN after redirection on command line ...
Hi Bob,
I'm not sure if there is a really clean solution to your problem.
To achieve the desired behavior, you would need to:
- find out which device should become your new stdin
(as you noticed, /dev/tty isn't necessarily the right choice), and
- redirect the stream 'stdin' to take its input from that device.
Finding the appropriate device may be anywhere between not too hard and
impossible. In the easy case, stdout or stderr refer to the TTY you want
to use. In the worst case, they have been redirected to files or closed
entirely, and your process has detached from its controlling terminal
(i.e., become a daemon) - in this scenario, there'd be no reasonable
guess which device to attach to.
Let's assume a simple case - stdout refers to a TTY.
You could of course just call dup2( 1, 0 ) to duplicate the stdout
file descriptor and have the duplicate your current stdin fd. The
problem is that the (FILE) stream object represented by *stdin will not
be aware of this change. There is the fdopen() function to wrap a FILE
object around an existing file descriptor, but that will allocate a new
object, not use an existing one...
...and alas, *stdin/-out/-err are static _objects_ - so we cannot merely
replace stdin by a new pointer.
You could try to flush and rewind the stdin stream, then call dup2( 1,
0 ) to replace the stdin file descriptor.
I'd suggest, though, to provide your input file via a command line
argument and have a few custom input functions that will read either
from that file or, once it reached EOF, the original stdin.
Cheers,
Thomas
-----Original Message-----
From: Bob Selby [mailto:robert.selby@snellgroup.com]
Sent: Mittwoch, 2. Mai 2012 10:46
To: ostech-core_os
Subject: Restoring STDIN after redirection on...
View Full Message
|
|
|
|
|
|
Thomas Haupt
|
RE: Restoring STDIN after redirection on command line ...
|
|
Thomas Haupt
05/02/2012 7:38 AM
post92880
|
RE: Restoring STDIN after redirection on command line ...
Glad to help. :)
- Thomas
-----Original Message-----
From: Robert Selby [mailto:Robert.Selby@snellgroup.com]
Sent: Mittwoch, 2. Mai 2012 13:34
To: ostech-core_os@community.qnx.com
Subject: RE: Restoring STDIN after redirection on command line ...
Very true ...
fc = fdopen(dup2(1, 0), "r");
seems to work OK too :-)
Thanks very much for the help :-)
Bob Selby
Senior Engineer, Software
Snell
Innovation in the
Multi-Screen World
T +44 (0) 118 921 4592 (direct)
T +44 (0) 118 986 6123 (switchboard)
F +44 (0) 118 975 4920
snellgroup.com
Hartman House, Danehill, Lower Earley, Reading, Berkshire, RG6 4PB UK
Routing | Modular Infrastructure | Conversion & Restoration | Live Production | Automation & Media Management | Control & Monitoring
-----Original Message-----
From: Thomas Haupt [mailto:thaupt@qnx.com]
Sent: 02 May 2012 12:29
To: 'ostech-core_os@community.qnx.com'
Subject: RE: Restoring STDIN after redirection on command line ...
Hi Bob,
that looks mostly reasonable. I'd still add a 'dup' or 'dup2', though, to have separate file descriptors for stdin and stdout.
Cheers,
Thomas
-----Original Message-----
From: Robert Selby [mailto:Robert.Selby@snellgroup.com]
Sent: Mittwoch, 2. Mai 2012 13:12
To: ostech-core_os@community.qnx.com
Subject: RE: Restoring STDIN after redirection on command line ...
Thanks for that :-)
I tried the following for "util < scriptfile" and it seems to do what I want ...
-----------------------------------------------------
FILE * fc = stdin;
...
fgets(fc, ... // Reads from redirected script file ...
On EOF I do ...
fclose(fc);
fc = fdopen(STDOUT_FILENO, "r") ) == NULL ) ...
fgets(fc, ... // Reads from keyboard
...
-----------------------------------------------------
Bob Selby
Senior Engineer, Software
Snell
Innovation in the
Multi-Screen World
T +44 (0) 118 921 4592 (direct)
T +44 (0) 118 986 6123 (switchboard)
F +44 (0) 118 975 4920
snellgroup.com
Hartman House, Danehill, Lower Earley, Reading, Berkshire, RG6 4PB UK
Routing | Modular Infrastructure | Conversion & Restoration | Live Production | Automation & Media Management | Control
& Monitoring
-----Original Message-----
From: Thomas Haupt [mailto:thaupt@qnx.com]
Sent: 02 May 2012 11:24
To: 'ostech-core_os@community.qnx.com'
Subject: RE: Restoring STDIN after redirection on command line ...
Hi Bob,
I'm not sure if there is a really clean solution to your problem.
To achieve the desired behavior, you would need to:
- find out which device should become your new stdin
(as you noticed, /dev/tty isn't necessarily the right choice), and
- redirect the stream 'stdin' to take its input from that device.
Finding the appropriate device may be anywhere between not too hard and impossible. In the easy case, stdout or stderr
refer to the TTY you want to use. In the worst case, they have been redirected to files or closed entirely, and your
process has detached from its controlling terminal (i.e., become a daemon) - in this scenario, there'd be no reasonable
guess which device to attach to.
Let's assume a simple case - stdout refers to a TTY.
You could of course just call dup2( 1, 0 ) to duplicate the stdout file descriptor and have the duplicate your current
stdin fd. The problem is that the (FILE) stream object represented by *stdin will not be aware of this change. There is
the fdopen() function to wrap a FILE object around an existing file descriptor, but that will allocate a new object,
not use an existing one...
...and alas, *stdin/-out/-err are static _objects_ - so we cannot merely replace stdin by a new pointer.
You could try to flush and rewind the stdin stream, then call dup2( 1,
0 ) to replace the stdin file descriptor.
I'd suggest, though, to provide your input file via a command line argument and have a few custom input functions that
will read either from that file or, once it...
View Full Message
|
|
|
|
|
|
