Questions tagged [unix]
For questions about the Unix operating system.
75
questions
7
votes
2answers
1k views
What are the "other crontabs" that /etc/crontab refer to? [closed]
The /etc/crontab file on ubuntu has a header that reads:
# /etc/crontab: system-wide crontab
# Unlike any other crontab you don't have to run the `crontab'
# command to install the new version when ...
15
votes
1answer
2k views
How would old software using the SIGPIPE signal really work if it were to manage _many_ pipes?
I'm wondering what was the thinking behind having a SIGPIPE signal.
From my own experience, the first thing I do is turn off that signal (SIGIGN) and use the return value of the calls to make sure it ...
36
votes
3answers
3k views
Why does make only accept tab-indentation?
The syntax for Makefiles requires that indented lines start with a tab, and not a space. So far as I can tell, this has been the case even for very early implementations of make. But even modern-day ...
9
votes
1answer
1k views
Is it true that "do ... done" blocks in Bash do not end with "od" because od existed before Bash/Bourne shell?
The Wikipedia page about od says:
Since it predates the Bourne shell, its existence causes an inconsistency in the do loop syntax. Other loops and logical blocks are opened by the name, and closed by ...
1
vote
1answer
319 views
Did DEMOS have a C compiler?
DEMOS was a Soviet operating system derived from BSD Unix. The answer to this question shows that the familiar, English-derived BSD commands were essentially the same in DEMOS.
Did DEMOS have a C ...
6
votes
2answers
300 views
DEMOS commands: Cyrillic or Roman letters? Uppercase or lowercase?
DEMOS was a Soviet operating system derived from BSD Unix.
Commands in BSD are derived from English words. Did DEMOS use these same commands, develop their own commands but retain the Roman alphabet,...
14
votes
3answers
2k views
What were the differences between Xenix and Unix?
According to https://en.wikipedia.org/wiki/Xenix by the beginning of the nineties, SCO was selling 32-bit 386 versions of both Xenix and Unix. According to https://news.ycombinator.com/item?id=...
39
votes
1answer
7k views
What was "the shrinkwrap issue?"
I first read "Alice in UNIX Land" (by Lincoln Spector, Texas Computer Currents, Sept. 1989), probably around the time when it was written — and at that time didn't understand very many of ...
1
vote
2answers
603 views
Does an OS, in particular Unix, need special support for terminal colors? [closed]
Also of interest, would be the first OS to support color graphics in other ways (assuming it wasn't a Unix).
Background: I'm thinking of playing around with Unix v6 due to all the material available, ...
7
votes
1answer
806 views
Unix: Why was five (SysV) released *after* seven (V7)?
AT&T released UNIX Version 7 (seven) in 1979.
The same company released UNIX System V (five) in 1983.
Why did the later release have a lower number?
7
votes
3answers
1k views
Why does -z and -n exist in most shells and /bin/test?
The test command on Unix-like systems provides two special syntax forms for checking whether a string is empty or not:
test -z "$foo" # the length of $foo is zero
test -n "$foo" # ...
17
votes
1answer
667 views
Where and when did the ".s" suffix for assembly-language source files originate?
The closest I was able to find on StackOverflow is What are .S files?, in which no answerer addresses why we use .s for assembly. (And .S for preprocessor/macro assembly; and gcc -S to produce ...
11
votes
2answers
1k views
Why is the Unix epoch January 1st 1970?
In honor of this weekend being 1,600,000,000 (1.6 billion) seconds since the Unix epoch, I was wondering if anyone knows why January 1st 1970 was chosen?
According to Wikipedia,
The earliest versions ...
30
votes
6answers
8k views
What are the major technical difference between Multics and Unix?
From the naming of operating system only i.e Unix = Uniplexed Information and Computing Service vs Multics = Multiplexed Information and Computing Service, I was first having a misconception that the ...
10
votes
2answers
786 views
Trying to understand some assembly syntax in the Unix v7 write system call
so here is the code: (which comes from here, I've also verified this source is in my unix v7 distribution). For reference, this is running on a PDP-11 simulated with the simh program (so please keep ...
18
votes
1answer
2k views
Identifying late 1990s embedded 486 UNIX-like system
I'm trying to identify the operating system on a Thermo-CRS C500 robot arm controller. From the specifications I know it runs on a 100 MHz 486 processor, and has 4 MB RAM and 2MB of flash/NVRAM ...
12
votes
2answers
3k views
How did the /dev file system work in early Unix?
UNIX did not have support for virtual file systems (vnodes) until 1986.
S.R. Kleiman, “Vnodes: An Architecture for Multiple File System Types in Sun UNIX,” Summer USENIX 1986
I remember this quite ...
5
votes
3answers
724 views
What were the Major Public Access Unix Systems Available in the 1980s-90s?
Back in the 1980s-90s, using a UNIX system required running expensive servers or paying for timesharing service, so they were beyond the reach of most individuals, and only available to members in ...
40
votes
1answer
7k views
What warning was given on attempting to post to USENET, circa 1990?
I recall a confirmation/warning message that read something like
"this will post to thousands of sites... are you sure?"
What was a typical such message in the days of pay-per-minute dialup access?
17
votes
1answer
379 views
What proprietary AT&T code/features were removed in BSD Net1 (/2), and BSD 4.4 Lite (/2) from the original 4.3BSD codebase?
Background
Although BSD and its source code was freely available under the original BSD licenses, but it only covered the portion of the code which copyright was owned by Regents of the University of ...
39
votes
6answers
10k views
How should we interpret Dave Cutler's criticism of Unix?
Dave Cutler is well known for his contributions to operating systems, having led the effort on VAX VMS at DEC and Windows NT at Microsoft. According to his Wikipedia page, he is also known for ...
14
votes
6answers
3k views
Using only one terminal, can I interrupt a process that's hung on very early Unix versions?
Within modern shells, I am able to leave a process via one of two control sequences:
Usually Ctrl+C will directly send SIGINT to the majority of shell commands (e.g. ping, echo, cat)
A few processes ...
0
votes
2answers
265 views
Role of Termcap under contemporary unices
A word of caution regarding this question: I'm more a userland than kernel person but have this nagging concern which I think belongs to kernel.
When configuring a system one decides on peripherals ...
27
votes
6answers
3k views
Why does UNIX ed not have a prompt by default
The line editor ed in UNIX/Linux has a "command mode" and an "insert mode" and there is no visual way to tell which mode you are in. However, there is a -p option that causes it to display a prompt ...
6
votes
1answer
305 views
Does the TELCOM program on the Tandy Model 100 support any Unix terminal–like control codes?
I've been connecting my Tandy Model 100 to a serial port on a Linux box via the TELCOM program with some success. The main downside is that in whatever the default terminfo/$TERM setting it gets, a ...
5
votes
1answer
230 views
How to test a chat script with a uucp linux and uucp(server) unix?
I like to play with old networks, uucp is really and advanced(is from the 1978) for that time.
I have setup a uucp server in a tru64 unix server.
On tru64 server
I have edit /etc/inetd.conf
uucp ...
13
votes
0answers
340 views
Unix on the H11?
I'm curious if anyone is aware of actual uses of Unix on the Heathkit H11? I don't see any technical reason a memory-expanded H11 couldn't run Unix, but can't find any examples of it doing so.
13
votes
2answers
3k views
Could you use uppercase or special characters in a password in early Unix?
This article is about Ken Thompson's old Unix password hash being cracked. One line in the article intrigues:
"Even an exhaustive search over all lower-case letters and digits took several days (...
58
votes
1answer
12k views
When was the famous "sudo warning" introduced? Under what background? By whom?
On all Unix-like operating systems, sudo is often provided as the standard package for executing commands as superuser (or an alternative user). When sudo is invoked by the user for the first time, ...
7
votes
2answers
604 views
How to setup a teletype to a unix shell
So, recently I've been researching old tech because I want to write some fiction about some typewriter that can access the command line(yep) that shows up in many youtube videos like This one. I want ...
13
votes
2answers
581 views
Unix utility "smiley" to decode emoticons: Where to get it?
I remember in the 90s, there existed a Unix command line utility named smiley that decoded emoticons. A sample use would be like this (the output is likely not the exact output the program gave):
$ ...
7
votes
1answer
329 views
WEGA operating system origins
I just recently stumbled across information about DDR minicomputer P8000 and its unixoid operating system WEGA. The website above as well as Wikipedia seem to claim some compatibility or even ...
43
votes
9answers
8k views
What was the point of separating stdout and stderr?
I occasionally need to work with console commands and 100% of the time I want to redirect my output to a file I fail to redirect stderr as well as stdout the first time. I can't think of a single ...
26
votes
6answers
6k views
Was Unix ever a single-user OS?
I've been told that Unix started out as a Phone Switch OS and was not a multi-user OS at some time in its infancy.
As I'm always willing to learn new things, are there any greybeards around here ...
8
votes
2answers
720 views
Does "Unix" and "UNIX" represent the same thing?
In some articles I see the word Unix written as "Unix", while in other articles I see the word Unix written as "UNIX".
Does "Unix" and "UNIX" represent the same thing?
10
votes
6answers
1k views
What happens when a terminal (like a VT100) is connected to a computer?
I'm wondering what's the sequence of actions when a terminal (like a VT100) is plugged into a serial port of a computer? Especially, how the connection of this terminal is detected, and how the ...
15
votes
1answer
693 views
Why does AT&T syntax use * and $?
In a comment to an answer about AT&T assembly syntax, another-dave asked the following:
DEC used #foo for an immediate operand in -11 assemblers; the Unix guys apparently preferred $foo, which ...
5
votes
1answer
382 views
What was the first publication documenting AT&T syntax assembly language?
What was the first publication to document what is (now) known as AT&T syntax assembly language?
21
votes
1answer
2k views
Process model in early UNIX
I heard recently that the process model in very early variants of UNIX was quite a bit different to the fork/exec model used nowadays.
How did it differ from the current state?
1
vote
1answer
274 views
Netscape has detected a /.netscape/lock file
My computer is saying that my netscape file is being used by a host that says it is located in Boulder Colorodo. It is coming from a wierd IP address. I just plugged my ethernet cable to use the ...
50
votes
10answers
10k views
Why was preemptive multitasking so slow in coming to consumer OS's?
Preemptive (rather than cooperative) multitasking was a highly-touted feature for PC's in 1996, with its inclusion in Windows 95 for the first time. It was also highly-touted for 2001 Macs when ...
12
votes
2answers
883 views
Origin of "tarball"
It seems to be common (at least among my section of the world's *NIX users) to refer to "tape archives" made with GNU tar or similar as "tarballs". I always thought this was a slightly odd choice, ...
1
vote
1answer
559 views
How do I compile C code with the IRIX X Window System?
I have typed out a rather large file in C code that is defining OpenGL graphics and will draw a triangle on the screen. While I know all of the functions of the X Windowing System, I do not know how ...
13
votes
1answer
659 views
Where did /usr/mdec come from?
On UNIX, the boot code is traditionally found in the directory /usr/mdec. Some modern UNIX variants keep this tradition up (e.g. OpenBSD) while others have changed the directory layout (e.g. FreeBSD)....
70
votes
3answers
9k views
Why did Unix use slash as the directory separator?
The Unix designers came from the GE/MIT Multics project, and Multics inspired some Unix features. In particular, Multics has a hierarchical filesystem, and so does Unix.
On Multics, pathnames were of ...
6
votes
1answer
635 views
On the use of the "Code Improver"
Very early C compilers, (mostly K&R C, as seen in UNIX V6, or this compiler for the Atari ST called "Megamax C") came with a "code improver". This was apparently a separate binary, named c2, and ...
8
votes
0answers
231 views
A learning gomoku in Lisp
Years ago I played a version of gomoku that was written in Lisp that learned as you played. After a few rounds, it became nearly unbeatable. This was on Unix System III on a small PDP-11.
I have ...
65
votes
4answers
23k views
Why is Windows using CR+LF and Unix just LF when Unix is the older system?
Windows and MS-DOS use the control characters CR+LF (carriage return, line feed) for new lines, while Unix uses just LF.
As far as I know CR+LF made sense for systems controlling a real teletypewriter,...
16
votes
4answers
3k views
What determines which architecture an a.out executable runs on?
The ELF file format has an e_machine field in the header, which specifies which ISA the executable expects. And the e_ident structure also has an EI_OSABI field that specifies which ABI the executable ...
34
votes
2answers
5k views
Why was UNIX never backported to the PDP-7?
Originally, UNIX was written in PDP-7 assembly, and then in PDP-11 assembly, but then when UNIX V4 began to be re-written in C in 1973 and was run mostly on the PDP-11.
So far as I can tell, there ...