20 Oct
2019
20 Oct
'19
7:25 p.m.
Bakul Shah:
Being an OS student I had read "The Unix Timesharing System" paper by
Ritchie and Thompson and had wanted to use Unix years before I actually
had the chance. I don't remember an "Aha!" moment but I took to it like
a duck to water. Most everything felt just so comfortable and right.
It was very much as I had imagined it to be.
=====
That's more or less what it was like to me. Not so much
an aha! moment, more just a feeling of coming home. It
took a while to understand the different way things worked
in UNIX (I had previously used TOPS-10 for several years)
but as it all sank in it felt more and more right.
C felt the same way. It took me a while to grok the pointer
syntax (I had done a lot of MACRO-10 programming so I certainly
understood the concept, just not how it fit into the higher-
level language), but things like the three-clause condition
in for so that all control for a loop could be in one place
were just magically right.
I don't think I read the CACM paper before I touched UNIX,
but I had read both editions of Software Tools, so my brain
was perhaps pre-seeded with some of the ideas.
Norman Wilson
Toronto ON
20 Oct
20 Oct
8:12 p.m.
New subject: What was your "Aha, Unix!" moment?
On Sun, Oct 20, 2019 at 03:25:52PM -0400, Norman Wilson wrote:
That's more or less what it was like to me. Not
so much
an aha! moment, more just a feeling of coming home. It
took a while to understand the different way things worked
in UNIX (I had previously used TOPS-10 for several years)
but as it all sank in it felt more and more right.
Up to my 30s I had only vaguely known about computers, it definitely wasn't my
thing, I was a musician. But one day I found myself buying a $3k Packard Bell
486, learnt DOS and began buying CD-ROMS with software often taken straight
off the big ftp sites. That is how I discovered Unix and how much better than
DOS it was. Within a year (1994) I was running my own Linux system. There was
a lot of stuff being ported from Solaris and the BSDs and I was learning C
just to build utilities I wanted, but if there was a 'killer app' for me that
was the aha! moment, it was a close contest between adventure and ching.
The odd thing was that adventure was certainly playable, but ching only
existed as a weird hybrid of shell script and two C programs and used some
kind of manpage macros and I didn't understand why but I loved it. That was my
introduction really to the Unix tools philosophy and suddenly the way my Linux
system worked made sense. Being also a history buff I wanted to know how this
all happened and that led to Don Libes and Life With Unix and my fate was
sealed.
--
I love deadlines. I love the whooshing noise as they fly by.
21 Oct
21 Oct
2:31 a.m.
New subject: What was your "Aha, Unix!" moment?
i was writing the small utilities for the first
pdp-11 unix. (rm ls date ....)
so, cd was next.
% pwd
/usr/ken
% cd /tmp
% pwd
/usr/ken
Aha!
On Sun, Oct 20, 2019 at 1:12 PM Sean Dwyer <ewe2(a)ewe2.ninja> wrote:
On Sun, Oct 20, 2019 at 03:25:52PM -0400, Norman Wilson wrote:
That's more or less what it was like to me.
Not so much
an aha! moment, more just a feeling of coming home. It
took a while to understand the different way things worked
in UNIX (I had previously used TOPS-10 for several years)
but as it all sank in it felt more and more right.
Up to my 30s I had only vaguely known about computers, it definitely wasn't my
thing, I was a musician. But one day I found myself buying a $3k Packard Bell
486, learnt DOS and began buying CD-ROMS with software often taken straight
off the big ftp sites. That is how I discovered Unix and how much better than
DOS it was. Within a year (1994) I was running my own Linux system. There was
a lot of stuff being ported from Solaris and the BSDs and I was learning C
just to build utilities I wanted, but if there was a 'killer app' for me that
was the aha! moment, it was a close contest between adventure and ching.
The odd thing was that adventure was certainly playable, but ching only
existed as a weird hybrid of shell script and two C programs and used some
kind of manpage macros and I didn't understand why but I loved it. That was my
introduction really to the Unix tools philosophy and suddenly the way my Linux
system worked made sense. Being also a history buff I wanted to know how this
all happened and that led to Don Libes and Life With Unix and my fate was
sealed.
--
I love deadlines. I love the whooshing noise as they fly by. 
2:37 a.m.
New subject: What was your "Aha, Unix!" moment?
On Sun, Oct 20, 2019 at 07:31:55PM -0700, Ken Thompson via TUHS wrote:
i was writing the small utilities for the first
pdp-11 unix. (rm ls date ....)
so, cd was next.
% pwd
/usr/ken
% cd /tmp
% pwd
/usr/ken
Aha!
As in, 'cd' has to be built into the shell. If it's external, the forked
child gets to change directory and the parent shell doesn't. I'm just
putting this in for those who didn't spot the nuance immediately -- took
me a few tens of seconds.
But wasn't "chdir" built into the PDP-7 Unix shell?
Thanks, Warren
22 Oct
22 Oct
5:25 a.m.
New subject: What was your "Aha, Unix!" moment?
On 2019-Oct-21 12:37:20 +1000, Warren Toomey <wkt(a)tuhs.org> wrote:
As in, 'cd' has to be built into the shell.
If it's external, the forked
child gets to change directory and the parent shell doesn't. I'm just
putting this in for those who didn't spot the nuance immediately -- took
me a few tens of seconds.
I'm still amazed at the number of people who don't get this and write
shellscripts that save the working directory on entry and do an explicit cd
at the end (usually without considering that the shellscript could die at
other locations).
--
Peter Jeremy
6:29 a.m.
New subject: What was your "Aha, Unix!" moment?
On Mon, Oct 21, 2019 at 12:37:20PM +1000, Warren Toomey wrote:
On Sun, Oct 20, 2019 at 07:31:55PM -0700, Ken Thompson
via TUHS wrote:
Aha indeed, Ken & Warren!
chdir seems to be a syscall in 7 (sys4.c), its handling in sh mostly in xec.c,
a real workout for the preprocessor ;)
--
I love deadlines. I love the whooshing noise as they fly by.
i was writing the small utilities for the first
pdp-11 unix. (rm ls date ....)
so, cd was next.
% pwd
/usr/ken
% cd /tmp
% pwd
/usr/ken
Aha!
As in, 'cd' has to be built into the shell. If it's external, the forked
child gets to change directory and the parent shell doesn't. I'm just
putting this in for those who didn't spot the nuance immediately -- took
me a few tens of seconds.
But wasn't "chdir" built into the PDP-7 Unix shell?
Thanks, Warren 
21 Oct
21 Oct
2:40 a.m.
New subject: What was your "Aha, Unix!" moment?
On Sun, 20 Oct 2019 19:31:55 -0700 Ken Thompson via TUHS <tuhs(a)minnie.tuhs.org>
wrote:
i was writing the small utilities for the first
pdp-11 unix. (rm ls date ....)
so, cd was next.
% pwd
/usr/ken
% cd /tmp
% pwd
/usr/ken
Aha!
It was probably more like this:
% pwd
/usr/ken
?
Aha!
2:45 a.m.
New subject: What was your "Aha, Unix!" moment?
On Sun, Oct 20, 2019 at 07:31:55PM -0700, Ken Thompson via TUHS wrote:
i was writing the small utilities for the first
pdp-11 unix. (rm ls date ....)
so, cd was next.
% pwd
/usr/ken
% cd /tmp
% pwd
/usr/ken
Aha!
I'm old and slow, had to think about that one. Aha indeed!
10:45 a.m.
New subject: What was your "Aha, Unix!" moment?
> % pwd
> /usr/ken
> % cd /tmp
> % pwd
> /usr/ken
>
> Aha!
I'm old and slow, had to think about that one.
Aha indeed!
I've actually been asking this (or, as a variation, how a child can set
environment in its parent) as an interview question for unix sysadmins for
the past fifteen or so years. Maybe one in three gets it.
The answer that I'm secretly hoping for, no one has ever yet given me:
hashbrown/home/jason-112719: /bin/pwd
/home/jason
hashbrown/home/jason-112720: ./cd.sh /tmp
hashbrown/home/jason-112721: /bin/pwd
/tmp
hashbrown/home/jason-112722: cat cd.sh
cat: cd.sh: No such file or directory
hashbrown/home/jason-112723: cat ~/cd.sh
#!/bin/sh
test -n "$1" && TARGET=$1 || TARGET=$HOME
( echo "call (int) chdir(\"$TARGET\")" ; echo detach ; echo quit ) |
gdb -q -p $PPID >/dev/null 2>&1 &
"With ptrace(2) all things are possible."
-Jason
11:55 a.m.
New subject: What was your "Aha, Unix!" moment?
You could cheat a little:
CHDIR=/usr/newFolder
echo “cd ${CHDIR}” > ./changeEnv
. ./changeEnv
Bill Corcoran
On Oct 21, 2019, at 6:52 AM,
"jason-tuhs(a)shalott.net" <jason-tuhs(a)shalott.net> wrote:
> % pwd
> /usr/ken
> % cd /tmp
> % pwd
> /usr/ken
>
> Aha!
I'm old and slow, had to think about that
one. Aha indeed!
I've actually been asking this (or, as a variation, how a child can set environment
in its parent) as an interview question for unix sysadmins for the past fifteen or so
years. Maybe one in three gets it.
The answer that I'm secretly hoping for, no one has ever yet given me:
hashbrown/home/jason-112719: /bin/pwd
/home/jason
hashbrown/home/jason-112720: ./cd.sh /tmp
hashbrown/home/jason-112721: /bin/pwd
/tmp
hashbrown/home/jason-112722: cat cd.sh
cat: cd.sh: No such file or directory
hashbrown/home/jason-112723: cat ~/cd.sh
#!/bin/sh
test -n "$1" && TARGET=$1 || TARGET=$HOME
( echo "call (int) chdir(\"$TARGET\")" ; echo detach ; echo quit ) |
gdb -q -p $PPID >/dev/null 2>&1 &
"With ptrace(2) all things are possible."
-Jason
22 Oct
22 Oct
5:19 a.m.
New subject: What was your "Aha, Unix!" moment?
On Oct 21, 2019, at 3:45 AM, jason-tuhs(a)shalott.net
wrote:
hashbrown/home/jason-112723: cat ~/cd.sh
#!/bin/sh
test -n "$1" && TARGET=$1 || TARGET=$HOME
( echo "call (int) chdir(\"$TARGET\")" ; echo detach ; echo quit ) |
gdb -q -p $PPID >/dev/null 2>&1 &
"With ptrace(2) all things are possible.”
I honestly don’t know whether to applaud or vomit.
Adam
1654
days inactive
1656
days old
10 comments
10 participants
participants (10)
-
Adam Thornton -
Bakul Shah -
jason-tuhs＠shalott.net -
Ken Thompson -
Larry McVoy -
Norman Wilson -
Peter Jeremy -
Sean Dwyer -
Warren Toomey -
William Corcoran