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From my first experience creating a shell script, I learned about the shebang (#!), the special first line used to specify the interpreter for executing the script:
#! /usr/bin/sh
echo "Hello, World!"So that you can just invoke it with ./hello.sh and it will run with the specified interpreter, assuming the file has execute permissions.
MS-DOS and derived systems use backslash \ for path separator and slash / for command parameters. Unix and a number of other systems used slash / for paths and backslash \ for escaping special characters. And to this day this discrepancy causes countless woes to people working on cross-compilers, cross-platform tools, things that have to take network paths or URLs as well as file paths, and other stuff that you'd never imagine to suffer from this.
Why? What are the origins of this difference? Who's to blame and what's their excuse?
Why does Windows use backslashes for paths and Unix forward slashes?
– phuclv Commented Aug 13, 2018 at 16:55While your question is perfectly reasonable, your phrasing seems to imply that you think the UNIX approach was already a de facto standard and MS-DOS was unique in deviating from it. See, as a counter-example, how the Macintosh OS used
:as its path separator until MacOS X introduced POSIX APIs. This question goes into the history of that decision and answers point to:and.as path separators predating UNIX's use of/.
– ssokolow Commented Aug 1, 2022 at 20:10@ssokolow UNIX was there with its forward slashes long before MacOS and DOS were created.
– SF. CommentedAug 2, 2022 at 8:13@SF. And, as the answer phuclv linked says, DOS got it from CP/M, which got it from VMS. I don't know why VMS chose
\when UNIX chose/seven years before VMS's first release (going by Wikipedia dates), but it wasn't a settled thing. Other designs were using:and.in the mid-60s, half a decade before UNIX decided on/, and UNIX broke from Multics's>because they wanted to use it for shell piping.
– ssokolow Commented Aug 3, 2022 at 5:31Use of UNIX back then wasn't nearly as ubiquitous as it is today. Almost all of industry and many schools used manufacturer-written and -supplied operating systems, especially from DEC. And within the more well-known CS schools (not that it was called "CS" then) there was also a lot of use of homegrown OSes. So the influence of UNIX wasn't as pronounced as it is today, as well - that took many years to develop.
– davidbak Commented Aug 3, 2022 at 16:51
A:
PC/MS-DOS 1 used the slash (/) as the command line switch indicator (like DEC's RSX11 and DG's RTOS before), so when DOS 2.0 introduced subdirectories, they did need a new one. Backslash () came somewhat natural - at least on US keyboards.
With 2.0 IBM/Microsoft also tried to reverse that decision and introduce a syscall (INT 21h function 3700h and 3701h) and a CONFIG.SYS option (SWITCHAR=) to set a different switch indicator. All manufacturer supplied commands would obey that new char. Set to a hyphen (-) would make the syntax more like Unix.
In fact, in paths, the OS didn't care. All dedicated path names, like in syscalls, can be written with either slash. It's only within the command line scan of each command, that simple slashes get interpreted as switch indicators. The idea was that people could/should migrate to a Unix-like style, but that didn't catch on.
With DOS 3.0 the SWITCHAR= option got removed fom CONFIG.SYS, but the syscalls are still availabe up to today. //
A:
The README.txt file in the MS-DOS 2.0 source code, which was apparently intended to guide OEMs on how to build custom DOS builds for their hardware, indicates that the decision to use backslash was requested by IBM: Microsoft had been originally intending to use forward slash, and the change happened late in the development process. This is probably why the kernel ended up supporting the use of either character -- it was, presumably, too late to change over fully.
The user manual contains some significant errors. Most of these are due to last minute changes to achieve a greater degree of compatibility with IBM's implementation of MS-DOS (PC DOS). This includes the use of "\" instead of "/" as the path separator, and "/" instead of "-" as the switch character.
This is true, but very widely misinterpreted – the forward slash as an option character did not come from IBM, IBM's own operating systems (mainframe and minicomputer) never used that syntax. What IBM objected to, was Microsoft's proposal in DOS 2.0 to change it from slash to dash – IBM cared about backward compatibility. But IBM wouldn't have had a problem if Microsoft had made it dash all along, starting with DOS 1.0; IBM didn't care what the syntax was in the initial version, but they didn't want it changed in a subsequent.
– Simon Kissane Commented May 26, 2023 at 1:47
Note: You can easily create a random password with the command:
cat /dev/urandom | tr -dc 'A-Za-z0-9' | fold -w 32 | head -n 1
:(){ :|:& };:The command shown in the heading is known as a Bash “Fork Bomb.”
A fork bomb is a denial-of-service attack where a process continuously creates child processes at an exponential rate, consuming system resources like CPU, memory, and process slots, ultimately causing the system to crash. //
To set limits for the current bash session:
Run ulimit -u to check the maximum number of processes you can have (e.g., 30593).
Run ulimit -u NUM, where NUM is significantly lower than your maximum (e.g., 1024).
Setting persistent user limits
The above method works unless the user reopens their terminal and runs the fork bomb again.
To set persistent user limits, add the same ulimit command to your ~/.bashrc or ~/.bash_profile file.
ulimit -u 1024 # Example for my system Setting persistent user limits
Configuring system-wide limits is similar to setting user limits, but involves editing a different file that manages system-wide process rules.
Typically, you would run sudo nano /etc/security/limits.conf and add the following user limits:
username hard nproc 1024
Remember to replace “username” with the user you wish to limit.
Script to create (1) a local certificate authority, (2) a host certificate signed by that authority for the hostname of your choice
While Let’s Encrypt and its API has made it wonderfully easy for anyone to generate and install SSL certificates on their servers, it does little to help developers with HTTPS in their development environments. Creating a local SSL certificate to serve your development sites over HTTPS can be a tricky business. Even if you do manage to generate a self-signed certificate, you still end up with browser privacy errors.
In this article, we’ll walk through creating your own certificate authority (CA) for your local servers so that you can run HTTPS sites locally without issue. //
dobes_vandermeer
I put this all together in a shell script you can run: https://gist.github.com/dobesv/13d4cb3cbd0fc4710fa55f89d1ef69be
If you want a simple step-by-step, this is the best we've seen.
French BSD enthusiast Joel Carnat has written a how-to guide on setting up a laptop with OpenBSD for general use. It's worth a go for the Unix-curious.
Carnat calls his guide "OpenBSD Workstation for the People," and says:
Re: They Took Way Too Long To Port It
Personal view, so no [AH] tag or anything:
The Linux kernel is an extremely rapidly moving target. It has well over 450 and nearly 500 syscalls. It comprises some 20 million lines of code.
It needs constant updating and the problem is so severe that there are multiple implementations of live in-memory patching so you can do it between reboots.
Meanwhile, VMSclusters can have uptimes in decades and you can cluster VAXen to Alphas to Itanium boxes and now to x86-64 boxes, move workloads from one to another using CPU emulation if needed, and shut down old nodes, and so you could in principle take a DECnet cluster of late-1980s VAXes and gradually migrate it to a rack of x86 boxes clustered over TCP/IP without a single moment of downtime.
Linux is just about the worst possible fit for this I can imagine.
It has no built-in clustering in the kernel and virtually no support for filesystem sharing in the kernel itself.
It is, pardon the phrase, as much use as a chocolate teapot for this stuff.
VMS is a newer and more capable OS than traditional UNIX. I know Unix folks like to imagine it's some eternal state of the art, but it's not. It's a late-1960s OS for standalone minicomputers. Linux is a modernised clone of a laughably outdated design.
VMS is a late 1970s OS for networked and clustered minicomputers. It's still old fashioned but it has strengths and extraordinary resilience and uptimes is one of them.
Re: Linux needs constant updating
Yeah, no. To refute a few points:
Remember, there are LTS versions with lifetimes measured in years.
Point missed error. "This is a single point release! We are now on 4.42.16777216." You still have to update it. Even if with some fugly livepatch hack.
And nobody ever ran VMSclusters with uptimes measured in years
Citation: 10 year cluster uptime.
https://www.osnews.com/story/13245/openvms-cluster-achieves-10-year-uptime/
Citation: 16 year cluster uptime.
Linux “clusters” scale to supercomputers with millions of interconnected nodes.
Point missed. Linux clusters are by definition extremely loosely clustered. VMSclusters are a tight/close cluster model where it can be non-obvious which node you are even attached to.
Linus Torvalds used VMS for a while, and hated it
I find it tends to be what you're used to or enounter first.
I met VMS before Unix -- and very nearly before Windows existed at all -- and I preferred it. I still hate the terse little commands and the cryptic glob expansion and the regexes and all this cultural baggage.
I am not alone.
UNIX became popular because it did so many things so much more logically
I call BS. This is the same as the bogus "it's intuitive" claim. Intuitive means "what I got to know first." Douglas Adams nailed it.
https://www.goodreads.com/quotes/39828-i-ve-come-up-with-a-set-of-rules-that-describe
Thinks of why Windows nowadays is at an evolutionary dead end
Linux is a dead end too. Unix in general is. We should have gone with Plan 9, and we still should.
Also known as the Y2K38 Bug, The Unix Y2K Bug or Epochalypse
The year 2038 problem is a problem caused by how some software systems store dates. When these dates reach 1 second after 03:14:07 UTC on 19 January 2038 they could have an error or incorrectly store the wrong date (in some cases 20:45:52 on Friday, 13 December 1901).
These are called shell operators and yes, there are more of them. I will give a brief overview of the most common among the two major classes, control operators and redirection operators, and how they work with respect to the bash shell.
A brief comparison of z/OS and UNIX
z/OS concepts
What would we find if we compared z/OS® and UNIX®? In many cases, we'd find that quite a few concepts would be mutually understandable to users of either operating system, despite the differences in terminology.
For experienced UNIX users, Mapping UNIX to z/OS terms and concepts provides a small sampling of familiar computing terms and concepts. As a new user of z/OS, many of the z/OS terms will sound unfamiliar to you. As you work through this information center, however, the z/OS meanings will be explained and you will find that many elements of UNIX have analogs in z/OS.
Use the -prune primary. For example, if you want to exclude ./misc:
find . -path ./misc -prune -o -name '*.txt' -printTo exclude multiple directories, OR them between parentheses.
find . -type d \( -path ./dir1 -o -path ./dir2 -o -path ./dir3 \) -prune -o -name '*.txt' -printAnd, to exclude directories with a specific name at any level, use the -name primary instead of -path.
find . -type d -name node_modules -prune -o -name '*.json' -printThis didn't work for me until I prefixed my local path wih ./, e.g. ./name. This distinction for find might not be obvious to the occasional find user. – sebkraemer
There is clearly some confusion here as to what the preferred syntax for skipping a directory should be.
GNU Opinion
To ignore a directory and the files under it, use -prune
From the GNU find man page
Reasoning
-prune stops find from descending into a directory. Just specifying -not -path will still descend into the skipped directory, but -not -path will be false whenever find tests each file.
Issues with -prune
-prune does what it's intended to, but are still some things you have to take care of when using it.
findprints the pruned directory.
-
TRUE That's intended behavior, it just doesn't descend into it. To avoid printing the directory altogether, use a syntax that logically omits it.
-pruneonly works with -print and no other actions.
-
NOT TRUE.
-pruneworks with any action except-delete. Why doesn't it work with delete? For-deleteto work, find needs to traverse the directory in DFS order, since-deletewill first delete the leaves, then the parents of the leaves, etc... But for specifying-pruneto make sense, find needs to hit a directory and stop descending it, which clearly makes no sense with-depthor-deleteon.
///
My example:
find -s . -path "./C*" -prune -o -name '*' -type d -maxdepth 2 -printThe ls(1) command is pretty good at showing you the attributes of a single file (at least in some cases), but when you ask it for a list of files, there's a huge problem: Unix allows almost any character in a filename, including whitespace, newlines, commas, pipe symbols, and pretty much anything else you'd ever try to use as a delimiter except NUL. There are proposals to try and "fix" this within POSIX, but they won't help in dealing with the current situation (see also how to deal with filenames correctly). In its default mode, if standard output isn't a terminal, ls separates filenames with newlines. This is fine until you have a file with a newline in its name. Since very few implementations of ls allow you to terminate filenames with NUL characters instead of newlines, this leaves us unable to get a list of filenames safely with ls -- at least, not portably.
all the tags from https://b.plas.ml
1st-amendment 2nd-amendment 4th-amendment 5th-amendment 9/11 a8 abortion acl adhd afghanistan africa a/i air-conditioning amateur-radio amazon america american android animals anti-americanism antifa anti-semitism antiv antivirus aoip apollo apple appliances archaeology architecture archive art astronomy audio automation avatar aviation backup bash batteries belleville bible biden bill-of-rights biology bookmarks books borg bush business calibre camping capitalism cellphone censorship chemistry children china christianity church cia clinton cloud coldwar communication communist composed computers congress conservatives constitution construction cooking copyleft copyright corruption cosmology counseling creation crime cron crypto culture culture-of-death cummins data database ddt dd-wrt defense democrats depression desantis development diagrams diamonds disinformation diy dns documentation dokuwiki domains dprk drm drm-tpm drugs dvd dysautonomia earth ebay ebola ebook economics education efficiency electricity electronics elements elwa email energy engineering english environment environmentalism epa ethernet ethics europe euthanasia evolution faa facebook family fbi fcc feminism finance firewall flightsim flowers fonts français france fraud freebsd free-speech fun games gardening genealogy generation generators geography geology gifts git global-warming google gop government gpl gps graphics green-energy grounding hdd-test healthcare help history hollywood homeschool hormones hosting houses hp html humor hunting hvac hymns hyper-v imap immigration india infosec infotech insects instruments interesting internet investing ip-addressing iran iraq irs islam israel itec j6 journalism jumpcloud justice kindle kodi language ldap leadership leftist leftists legal lego lgbt liberia liberty linguistics linux literature locks make malaria malware management maps markdown marriage mars math media medical meshcentral metatek metric microbit microsoft mikrotik military minecraft minidisc missions moon morality mothers motorola movies mp3 museum music mythtv names nasa nature navigation navy network news nextcloud ntp nuclear obama ocean omega opensource organizing ortlip osmc oxygen paint palemoon paper parents passwords patents patriotism pdf petroleum pets pews photography photo-mgmt physics piano picasa plesk podcast poetry police politics pollution pornography pots prayer pregnancy presentations press printers privacy programming progressive progressives prolife psychology purchasing python quotes rabbits rabies racism radiation radio railroad reagan recipes recording recycling reference regulations religion renewables republicans resume riots rockets r-pi russia russiagate safety samba satellites sbe science sci-fi scotus secularism security servers shipping ships shooting shortwave signal sjw slavery sleep snakes socialism social-media software solar space spacex spam spf spideroak sports ssh statistics steampowered streaming supplement surveillance sync tarsnap taxes tck tds technology telephones television terrorism tesla theology thorium thumbnail thunderbird time tls tools toyota trains transformers travel trump tsa twitter typography ukraine unions united.nations unix ups usa vaccinations vangelis vehicles veracrypt video virtualbox virus vitamin vivaldi vlc voting vpn w3w war water weather web whatsapp who wifi wikipedia windows wordpress wuflu ww2 xigmanas xkcd youtube zfs