7 Nov
2017
7 Nov
'17
4:21 a.m.
I wrote a snippet from my K&R C studies to convert tabs and backspaces
to \t \b to display them, the code looks like this:
/* ex 1-8 */
main()
{
int c, sf;
while((c = getchar()) != EOF) {
if(c == '\t')
printf("\\t");
if(c == '\b')
printf("\\b");
else
putchar(c);
}
}
I'm not looking for code review, but the code is intended to replace the
tabs and backspaces with \t and \b respectively, but I haven't been able
to test it because I can't seem to make a backspace character appear in
input. In later unices, ^V followed by the backspace would work, but
that's not part of v7. Backspace itself is my erase character, so
anytime I just type it, it backspaces :).
Thanks,
Will
--
GPG Fingerprint: 68F4 B3BD 1730 555A 4462 7D45 3EAA 5B6D A982 BAAF
7 Nov
7 Nov
4:34 a.m.
Will Senn <will.senn(a)gmail.com> wrote:
I'm not looking for code review, but the code is
intended to replace the
tabs and backspaces with \t and \b respectively, but I haven't been able
to test it because I can't seem to make a backspace character appear in
input. In later unices, ^V followed by the backspace would work, but
that's not part of v7. Backspace itself is my erase character, so
anytime I just type it, it backspaces :).
awk 'BEGIN { print "a\bc\td" ; exit }' | your-program
Enjoy,
Arnold
P.S. The exit is needed for V7 awk, IIRC, not modern ones.
4:49 a.m.
On 11/6/17 10:34 PM, arnold(a)skeeve.com wrote:
Will Senn <will.senn(a)gmail.com> wrote:
This is a good idea, but... Here's my results from just running awk for
\t, \n, and \b:
$ awk 'BEGIN { print "a\tb" ; exit }';
a b
$ awk 'BEGIN { print "a\nb" ; exit }'
anb
$ awk 'BEGIN { print "a\bb" ; exit }'
abb
$
Strange. It looks like it's just ignoring the backslash in the case of
\n and \b.
Will
--
GPG Fingerprint: 68F4 B3BD 1730 555A 4462 7D45 3EAA 5B6D A982 BAAF
I'm not looking for code review, but the
code is intended to replace the
tabs and backspaces with \t and \b respectively, but I haven't been able
to test it because I can't seem to make a backspace character appear in
input. In later unices, ^V followed by the backspace would work, but
that's not part of v7. Backspace itself is my erase character, so
anytime I just type it, it backspaces :).
awk 'BEGIN { print
"a\bc\td" ; exit }' | your-program
Enjoy,
Arnold
P.S. The exit is needed for V7 awk, IIRC, not modern ones.
5 a.m.
On 11/6/17 10:49 PM, Will Senn wrote:
On 11/6/17 10:34 PM, arnold(a)skeeve.com wrote:
I wrote a c program to print a string in line with the suggestion to use
awk and my code worked, but it's still odd that the above didn't work.
Will
--
GPG Fingerprint: 68F4 B3BD 1730 555A 4462 7D45 3EAA 5B6D A982 BAAF
Will Senn <will.senn(a)gmail.com> wrote:
This is a good idea, but... Here's my results from just running awk
for \t, \n, and \b:
$ awk 'BEGIN { print "a\tb" ; exit }';
a b
$ awk 'BEGIN { print "a\nb" ; exit }'
anb
$ awk 'BEGIN { print "a\bb" ; exit }'
abb
$
Strange. It looks like it's just ignoring the backslash in the case of
\n and \b.
Will
I'm not looking for code review, but the
code is intended to replace
the
tabs and backspaces with \t and \b respectively, but I haven't been
able
to test it because I can't seem to make a backspace character appear in
input. In later unices, ^V followed by the backspace would work, but
that's not part of v7. Backspace itself is my erase character, so
anytime I just type it, it backspaces :).
awk 'BEGIN { print
"a\bc\td" ; exit }' | your-program
Enjoy,
Arnold
P.S. The exit is needed for V7 awk, IIRC, not modern ones.
8:08 a.m.
Will Senn <will.senn(a)gmail.com> wrote:
I wrote a c program to print a string in line with the
suggestion to use
awk and my code worked, but it's still odd that the above didn't work.
The V7 awk was really primitive. Another idea that occurred to me:
stty erase #
and then you can enter a literal backspace on the command line.
HTH,
Arnold
9:07 a.m.
I'm not looking for code review, but the code is
intended to replace
the tabs and backspaces with \t and \b respectively, but I haven't
been able to test it because I can't seem to make a backspace
character appear in input. In later unices, ^V followed by the
backspace would work, but that's not part of v7. Backspace itself is
my erase character, so anytime I just type it, it backspaces :).
This bit from the middle of sys/dev/tty.c seems to indicate that you
escape it with \:
} else {
mc = maptab[c];
if (c==tp->t_erase || c==tp->t_kill)
mc = c;
if (mc && (mc==c || (tp->t_flags&LCASE))) {
if (bp[-2] != '\\')
c = mc;
bp--;
}
}
On my test v7 system if I type backslash control-h:
# stty
speed 0 baud
erase = '^H'; kill = '^U'
even -nl echo -tabs
# echo \^H | od -c
0000000 \b \n
0000002
#
De
1:55 p.m.
On 11/7/17 3:07 AM, Dennis Boone wrote:
Thanks for the note. I thought about it and tried it out even though I
don't see the ^H (my cursor backs up a space).
After typing echo "\^H" | od -c, here's what it looks like:
$ echo "" | od -c
0000000 \b \n
0000002
So, sure enough there's a backspace in there and my code "sees" it too:
$ echo "" | 1-8
<<BACKSPACE>>
$
--
GPG Fingerprint: 68F4 B3BD 1730 555A 4462 7D45 3EAA 5B6D A982 BAAF
I'm not
looking for code review, but the code is intended to replace
the tabs and backspaces with \t and \b respectively, but I haven't
been able to test it because I can't seem to make a backspace
character appear in input. In later unices, ^V followed by the
backspace would work, but that's not part of v7. Backspace itself is
my erase character, so anytime I just type it, it backspaces :).
This bit from the middle of sys/dev/tty.c seems to indicate that you
escape it with \:
} else {
mc = maptab[c];
if (c==tp->t_erase || c==tp->t_kill)
mc = c;
if (mc && (mc==c || (tp->t_flags&LCASE))) {
if (bp[-2] != '\\')
c = mc;
bp--;
}
}
On my test v7 system if I type backslash control-h:
# stty
speed 0 baud
erase = '^H'; kill = '^U'
even -nl echo -tabs
# echo \^H | od -c
0000000 \b \n
0000002
#
De 
11:21 a.m.
On Mon, Nov 6, 2017, 11:21 PM Will Senn <will.senn(a)gmail.com> wrote:
I wrote a snippet from my K&R C studies to convert
tabs and backspaces
to \t \b to display them, the code looks like this:
/* ex 1-8 */
main()
{
int c, sf;
while((c = getchar()) != EOF) {
if(c == '\t')
printf("\\t");
if(c == '\b')
Shouldn't this be 'else if'? Otherwise, if you encounter a tab, you will
print '\t' and then call into the 'else' below after the test for
'\b' and
print c, which is a tab literal.
- Dan C.
printf("\\b");
else
putchar(c);
}
}
I'm not looking for code review, but the code is intended to replace the
tabs and backspaces with \t and \b respectively, but I haven't been able
to test it because I can't seem to make a backspace character appear in
input. In later unices, ^V followed by the backspace would work, but
that's not part of v7. Backspace itself is my erase character, so
anytime I just type it, it backspaces :).
Thanks,
Will
--
GPG Fingerprint: 68F4 B3BD 1730 555A 4462 7D45 3EAA 5B6D A982 BAAF
2:59 p.m.
while((c = getchar()) != EOF) {
if(c == '\t')
printf("\\t");
if(c == '\b')
Shouldn't this be 'else if'? Otherwise, if you encounter a tab, you
will print '\t' and then call into the 'else' below after the test
for
'\b' and print c, which is a tab literal.
- Dan C.
Yes it should - I was concentrating on the backspace thing and not being
careful enough about the code.
if(c== '\t')
printf("\\t");
else if(c == '\b')
printf("\\b");
else
putchar(c);
Thanks,
Will
3:33 p.m.
I have always been a proponent of generalizing /dev/zero such that it supports both block
and character mode, and the minor node number specifies the byte you get mapped into
memory or read from a file.
So then you could just make a character device /dev/backspace whose minor node number was
8, and /dev/beep whose minor node number was 7!
-Don
On 7 Nov 2017, at 05:21, Will Senn
<will.senn(a)gmail.com> wrote:
I wrote a snippet from my K&R C studies to convert tabs and backspaces to \t \b to
display them, the code looks like this:
/* ex 1-8 */
main()
{
int c, sf;
while((c = getchar()) != EOF) {
if(c == '\t')
printf("\\t");
if(c == '\b')
printf("\\b");
else
putchar(c);
}
}
I'm not looking for code review, but the code is intended to replace the tabs and
backspaces with \t and \b respectively, but I haven't been able to test it because I
can't seem to make a backspace character appear in input. In later unices, ^V
followed by the backspace would work, but that's not part of v7. Backspace itself is
my erase character, so anytime I just type it, it backspaces :).
Thanks,
Will
--
GPG Fingerprint: 68F4 B3BD 1730 555A 4462 7D45 3EAA 5B6D A982 BAAF
8 Nov
8 Nov
4:48 p.m.
Hi Will,
I can't seem to make a backspace character
dc(1) is handy for unhexdump.
$ echo 16i4108666F6F0AP | dc | sed -n l
A\bfoo$
$
--
Cheers, Ralph.
https://plus.google.com/+RalphCorderoy
2361
days inactive
2362
days old
10 comments
6 participants
participants (6)
-
arnold＠skeeve.com -
Dan Cross -
Dennis Boone -
Don Hopkins -
Ralph Corderoy -
Will Senn