Questions tagged [history]

The history of Unix systems and their main components. Please DO NOT USE this tag for shell-related questions; use "command-history" instead.

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836
votes
2answers
170k views

Why was '~' chosen to represent the home directory?

I have often wondered why the ~ (tilde) represents the home directory of a user. Is there a reason behind this, or is it just some infrequently used character?
422
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5answers
67k views

Why not use "which"? What to use then?

When looking for the path to an executable or checking what would happen if you enter a command name in a Unix shell, there's a plethora of different utilities (which, type, command, whence, where, ...
317
votes
4answers
76k views

What does "rc" in .bashrc stand for?

Is it "resource configuration", by any chance?
317
votes
5answers
86k views

What's the story behind Super Cow Powers?

As we know, apt-get has Super Cow Powers and aptitude does not: $ apt-get --help | grep -i cow This APT has Super Cow Powers. $ aptitude --help | grep -i cow ...
249
votes
7answers
116k views

Where did the "wheel" group get its name?

The wheel group on *nix computers typically refers to the group with some sort of root-like access. I've heard that on some *nixes it's the group of users with the right to run su, but on Linux that ...
227
votes
4answers
78k views

Why are tar archive formats switching to xz compression to replace bzip2 and what about gzip?

More and more tar archives use the xz format based on LZMA2 for compression instead of the traditional bzip2(bz2) compression. In fact kernel.org made a late "Good-bye bzip2" announcement, 27th Dec. ...
203
votes
8answers
101k views

Is Linux a Unix?

So, there are lots of different versions of Unix out there: HP-UX, AIX, BSD, etc. Linux is considered a Unix clone rather than an implementation of Unix. Are all the "real" Unices actual descendants ...
129
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5answers
92k views

What is the purpose of the hash command?

If you run hash it shows the path of all commands run since the hash was last reset (hash -r) [root@c04c ~]# hash hash: hash table empty [root@c04c ~]# whoami root [root@c04c ~]# hash hits ...
119
votes
9answers
11k views

On what systems is //foo/bar different from /foo/bar?

Throughout the POSIX specification, there's provision (1, 2, 3...) to allow implementations to treat a path starting with two / specially. A POSIX application (an application written to the POSIX ...
117
votes
6answers
23k views

If Linux is only a kernel, then how were its first versions used (without distribution)?

Linux is only a kernel, and if users want to use it, then they need a complete distribution. That being said, how were the first versions of Linux used when there were no Linux distributions?
96
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3answers
21k views

Why is the root directory denoted by a / sign?

I have done some research about this on Google, but the results were cloudy. Why is the / sign used to denote the root directory. Are there any solid reasons behind it?
93
votes
3answers
13k views

What does the letter 'u' mean in /dev/urandom?

I understand that reads to /dev/random may block, while reading /dev/urandom is guaranteed not to block. Where does the letter u come into this? What does it signify? Userspace? Unblocking? Micro? ...
91
votes
4answers
22k views

Why does Linux use LF as the newline character?

As far as I know, every operating system has a different way to mark the end of line (EOL) character. Commercial operating systems use carriage return for EOL (carriage return and line feed on Windows,...
82
votes
6answers
25k views

Why can't Linux usernames begin with numbers?

Is there a technical reason why? Is this an artifact from the early days of Linux or Unix, and if so is there a reason why it persists?
73
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6answers
55k views

What is a socket?

Could someone explain to me what a socket is? I see it in many acronyms in context of SSL, etc. Also, why is it called a socket? Is it purely because it was what a name they invented? Or was it the ...
72
votes
3answers
18k views

Why is 'umount' not spelled 'unmount'?

I am wondering if there is any historical or practical reason why the umount command is not unmount.
68
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5answers
11k views

What is GNU Info for?

I understand what GNU Info is and how to use it, but what is it for? Why does it exist in parallel to the man pages? Why not write detailed man pages rather than provide a separate utility?
67
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3answers
11k views

Why is Unix 'self-supporting'?

I was reading Ritchie and Thompson's paper about the Unix file system. They write, 'It is worth noting that the system is totally self-supporting'. Were the systems before Unix not self-supporting? In ...
66
votes
1answer
4k views

What did the sticky bit originally do when applied to files?

In various places one can see the "sticky bit" accused of nowadays being a complete misnomer, as its functionality nowadays is to affect the write permissions on directories and act as a restricted ...
62
votes
5answers
9k views

Why is there a * When There is Mention of Unix Throughout the Internet?

I've noticed that throughout the Internet, within forums and blog posts, Unix always has a * in the word, whether it is *nix or Un*x, as I noticed at the welcoming banner at the Unix StackExchange ...
61
votes
4answers
18k views

What did Ken Thompson mean when he said, "I'd spell creat with an 'e'."?

Ken Thompson, the creator of Unix, was once asked what he'd do if he had it to do over again. He said, "I'd spell creat with an 'e'." What is Ken referring to? Is there a "creat" command?
59
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5answers
13k views

How to save a command you entered without executing it? [duplicate]

Every Linux user has experienced this annoying thing: you begin typing a long and boring command, then realise you should have executed another one before. How to save the first one to execute it ...
59
votes
4answers
6k views

Why don't man pages have examples?

Is there a reason why most man pages don't include a few common examples? They usually explain all the possible options, but that makes it even harder for a beginner to understand how it's "usually" ...
58
votes
4answers
11k views

Is the shell ksh93 dead?

On 2013-01-10 Glenn Fowler posted this to the ast-users mailing list: As has been pointed out several times on the AST and UWIN lists, AT&T gives very little support to OpenSouce software, ...
57
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3answers
85k views

Why does Unix time start at 1970-01-01?

Why does Unix time start at 1970-01-01? Why not 1971-01-01 or any other date?
55
votes
5answers
9k views

Why does no one use the true Bourne shell as /bin/sh?

I've noticed that basically no system I've ever worked with has /bin/sh as a real executable. It's always a symlink to dash, bash in POSIX mode, or something similar. Why? What are the disadvantages ...
55
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2answers
7k views

Origin of 'root' account

What's the origin of root account? Where did it come from and why is it called root anyway? (Originally asked by @lizztheblizz on Twitter.)
54
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6answers
7k views

Is there any reason to have a shebang pointing at /bin/sh rather than /bin/bash?

In most shell scripts I've seen (besides ones I haven't written myself), I noticed that the shebang is set to #!/bin/sh. This doesn't really surprise me on older scripts, but it's there on fairly new ...
53
votes
3answers
18k views

Why is rm allowed to delete a file under ownership of a different user?

From the post Why can rm remove read-only files? I understand that rm just needs write permission on directory to remove the file. But I find it hard to digest the behaviour where we can easily delete ...
53
votes
1answer
16k views

When and how was the double-dash (--) introduced as an end of options delimiter in Unix/Linux?

I don't think the shell/utilities in historical Unix nor in something as "recent" as 4.4BSD supported using a double-dash(or two consecutive hyphens) as an end of options delimiter. With FreeBSD, you ...
52
votes
6answers
28k views

Single dashes `-` for single-character options, but double dashes `--` for words?

Where did the convention of using single dashes for letters and doubles dashes for words come from and why is continued to be used? For example if I type in ls --help, you see: -a, --all ...
51
votes
5answers
14k views

Intended use of ctrl+T in bash?

I noticed bash has a short cut for ctrl+T which swaps the last two characters before the cursor. I'm wondering why the engineers decided to include this. Was it inherited from a previous convention?...
47
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1answer
4k views

Were all Unix commands re-written in Linux?

I would like to know which commands were re-written for Linux and which were retained from Unix?
47
votes
2answers
44k views

Why is the Intel HD Graphics driver called i915?

The only references to i915 I can find are indeed to the linux kernel driver for the intel chips. Intel just seems to call them HD graphics whatever. Intel 915 seems to refer to some Pentium 4 ...
46
votes
1answer
6k views

Why is the UNIX system call kill named 'kill'?

I am curious about the history of the name, it seems to me that the 'kill' system call could have been named 'signal', and the 'signal' system call could have been named 'handle'. I was wondering ...
45
votes
3answers
11k views

Why is there a Linux kernel policy to never break user space?

I started thinking about this issue in the context of etiquette on the Linux Kernel Mailing list. As the world's best known and arguably most successful and important free software project, the Linux ...
44
votes
1answer
4k views

What's this I hear about First Edition Unix being restored?

I commented elsewhere that the source code of First Edition Unix had been restored from tapes. The response was amazement and a request for more information. What have people done? Who did it? ...
43
votes
4answers
5k views

Why are UNIX/POSIX system call namings so illegible?

What is the reason to use such untelling system call names like time and creat instead of getCurrentTimeSecs and createFile or, maybe more suitable on Unix get_current_time_secs and create_file. Which ...
42
votes
3answers
5k views

Why is dmesg called dmesg?

Is there any explanation/history behind the name of the command dmesg (which prints out some kernel messages)?
42
votes
5answers
21k views

What is the point of mv -f when default behavior already overwrites files?

The GNU Coreutils manual for mv says: -f --force Do not prompt the user before removing a destination file. However, this already seems to be the default behaviour for mv, so the -f option appears ...
42
votes
2answers
72k views

What does the "rc" stand for in /etc/rc.d? [duplicate]

Does anybody have an idea about the full form of rc.d in, for example, /etc/rc.d? It contains scripts to used to control the starting, stopping and restarting of daemons. But what exactly is the ...
41
votes
1answer
2k views

What happened to bzip1?

bzip2 had been a de facto standard for quite strong compression throughout many years already. I myself had typed the bzip2 command thousands of times so far, which makes me wonder - what happened to ...
40
votes
3answers
8k views

How do pipelines limit memory usage?

Brian Kernighan explains in this video the early Bell Labs attraction to small languages/programs being based on memory limitations A big machine would be 64 k-bytes--K, not M or G--and so that ...
39
votes
4answers
10k views

Does vi silently add a newline (LF) at the end of file?

I have trouble understanding a weird behavior: vi seems to add a newline (ASCII: LF, as it is a Unix (AIX) system) at the end of the file, when I did NOT specifically type it. I edit the file as such ...
39
votes
2answers
101k views

What is the concept behind "tty" in linux? [duplicate]

Where did the terminology "tty" come from in Linux?
38
votes
2answers
10k views

Why was '.' chosen to represent the current directory and '..' for parent directory?

After reading this question Why was '~' chosen to represent the home directory?, next obvious question on my mind was why '.' and '..' was used to represent current directory and parent ...
37
votes
3answers
7k views

When did Unix stop storing passwords in clear text?

When did Unix move away from storing clear text passwords in passwd? Also, when was the shadow file introduced?
37
votes
3answers
71k views

Comparing integers: arithmetic expression or conditional expression

In Bash, two integers can be compared using conditional expression arg1 OP arg2 OP is one of -eq, -ne, -lt, -le, -gt, or -ge. These arithmetic binary operators return true if arg1 is equal ...
37
votes
2answers
12k views

Is there a reason why the first element of a Zsh array is indexed by 1 instead of 0?

From my experience with modern programming and scripting languages, I believe most programmers are generally accustomed to referring to the first element of an array by 0 as index. Are there any ...
37
votes
2answers
3k views

Why do Unix man pages use double backticks in place of double quotes?

I've noticed that man pages and other documents formatted by Unix utilities often use double backticks `` followed by double single quotes '' to wrap quoted phrases instead of the double quote ...

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