Questions tagged [unix]

For questions about the Unix operating system.

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7
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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
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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
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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
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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
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1answer
314 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
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2answers
299 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
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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
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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
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2answers
600 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
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1answer
802 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?
6
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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
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1answer
645 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
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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
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6answers
7k 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
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2answers
780 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
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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
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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
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3answers
691 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
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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
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1answer
366 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 ...
38
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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
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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
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2answers
263 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
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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
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1answer
302 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
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1answer
227 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
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0answers
330 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
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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
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1answer
11k 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
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2answers
597 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
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2answers
571 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
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1answer
325 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
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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 ...
25
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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
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2answers
706 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
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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
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1answer
685 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
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1answer
375 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
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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
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1answer
273 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
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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
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2answers
870 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
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1answer
542 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
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1answer
655 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
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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 ...
5
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1answer
625 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
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0answers
230 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
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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
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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 ...
33
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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 ...