Unix is a multitasking, multi-user computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs.

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90
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How do I set up SSH so I don't have to type my password?

How do I set up SSH so I don't have to type my password when connecting to a host?
23
votes
0answers
20k views

ls -la symbolics… what does that last symbol mean?

Possible Duplicate: what does the @ mean on the output of ls on os x terminal? when I type ls -la I get this familiar output... drwxr-xr-x+ 38 kent staff 1292 Nov 6 11:09 . ...
142
votes
8answers
8k views

What do the parentheses and number after a Unix command or C function mean?

I keep seeing parentheses and a number after a command in Unix or Linux or C function. For example: man(8), ftok(2), mount(8), etc. What do these mean? I see them in man too.
17
votes
2answers
27k views

Allow specific user permission to read/write my folder

I have a folder /home/samantha/folder that I want to share with the user tom. He can read/write the folder. How do I do that? chown wouldn't do it because I still want to be able to be the owner of ...
20
votes
1answer
3k views

Is there a way to make bash more TAB friendly?

I use bash on both my Mac and as my cygwin shell. Overall, I'm quite pleased with it. My one complaint however is that its TAB completion isn't as good as Windows Command Line TAB completion. For ...
10
votes
3answers
13k views

How can I use ssh to run a command on a remote Unix machine and exit before the command completes?

How can I use ssh to run a command on a Unix machine and exit before the command completes? For instance, if I type ssh localhost 'sleep 60 &' ssh hangs on my terminal until sleep completes, ...
22
votes
6answers
1k views

Learning the basics of Linux/Unix [closed]

I would like to learn the basics of Linux; In contrast to tutorials that teach how to do common tasks with Ubuntu or something. I'm looking for a structured introduction, not a reference. Also I would ...
23
votes
9answers
20k views

How Unix is Mac OS X? [closed]

From my limited knowledge: The Unix OS coder assumes the user knows what they're doing etc. versus the Apple's you can only do it the way you are allowed to do it, etc. Compared to other variations ...
86
votes
15answers
41k views

How to execute a command whenever a file changes?

I want a quick and simple way to execute a command whenever a file changes. I want something very simple, something I will leave running on a terminal and close it whenever I'm finished working with ...
19
votes
10answers
15k views

Bash: Reset and Clear Commands

I have been using the command: reset to clear my terminal. Although I am pretty sure this is not what I should be doing. Reset, as the name suggests resets your entire terminal (changes lots of ...
167
votes
12answers
25k views

How can I change to the previous directory instead of going up?

I currently spend a lot of my working hours moving back and forth between two paths which are very far down the tree and divert from each other at root. It strikes me that my life would be a lot ...
40
votes
3answers
63k views

How to make new file permission inherit from the parent directory?

I have a directory called data. Then I am running a script under the user id 'robot'. robot writes to the data directory and update files inside. The idea is data is open for both me and robot to ...
109
votes
6answers
93k views

What is the “You have new mail” message in Linux/UNIX?

Sometimes, when I log into a box and 'su' to root, I get a cute little message saying I have mail (thank GOD it's not AOL). Where is this mail? What does it contain? Who/What sent it? How important ...
25
votes
3answers
5k views

What does the 'rc' in `.bashrc`, etc. mean?

Well, this is embarrassing. I feel like I just realised I don't know a loyal colleague's name after working with them for 10 years. "Hey, er... *cough!*, thanks for that great job you did on setting ...
15
votes
3answers
5k views

Use GNU screen as login “shell”

What's the best way to have screen automatically run when you open a new shell, whether by login, xterm, or anything else? I see the most common recommendation is to put exec screen in your regular ...
4
votes
2answers
19k views

How do I reset the $PATH variable on Mac OS X?

I've messed up my path variable, and now some apps that I run raise errors saying Command Not Found (error 127) for commands like date and sleep. These commands work fine when executed directly in the ...
11
votes
2answers
2k views

Unix: Files starting with a dash, -

Ok, I have a bunch of files starting with a dash, -. Which is not so good... and I want to rename them. In my particular case I would just like to put a character in front of them. I found the ...
10
votes
2answers
7k views

What does the @ in ls -al mean? [duplicate]

Possible Duplicate: ls -la symbolics… what does that last symbol mean? What does the @ in the below execution of ls -al mean? atom:Lib fak$ ls -al total 1056 drwxr-xr-x 5 fak staff ...
7
votes
4answers
4k views

Keep a program running after closing a console, after the program has started [duplicate]

Possible Duplicate: How do I detach a process from Terminal, entirely? I've a program running in a Unix console on a remote Unix computer. I (stupidly) didn't run it using nohup &, and ...
10
votes
3answers
2k views

Calling a script with ./bla.sh vs. . bla.sh

Can anybody explain to me what the shell does in the two examples A) and B) below? It obviously behaves differently, but I can't find out why the output is different. Example: Let's have a script in ...
9
votes
6answers
2k views

What is the difference between Unix and Linux?

I want to know what the actual difference between Unix and Linux is. Do they share the same kernel? Is Linux built on Unix? Do programs written for Linux work on Unix and vice-versa?
45
votes
2answers
21k views

Why does Windows use backslashes for paths and Unix forward slashes?

It annoys me having used Unix in college and now working on the Windows side. What's the history behind this decision? Anyone know why it worked out this way?
23
votes
3answers
41k views

How do I make sudo preserve my environment variables?

Using sudo 1.7.4p4 on Solaris 5.10 and sudo 1.6.7p5 on RHEL4 u6 I can't see how to preserve my environment variables, for instance $PYTHONPATH. I've added this line to sudoers, but it doesn't make any ...
2
votes
6answers
6k views

Automatically restart a Unix job if it goes down?

I have a job that I would like to "daemonize" on Unix: I want it to come up when the computer boots, and I want it to restart if it goes down. A simple way to do this is to setup a cronjob that runs ...
18
votes
9answers
9k views

Is Mac OS X open source?

I learned recently (on superuser) that Mac OS X uses the bash shell. I also know that OS X has a UNIX core. I was searching for information about OS X and Open Source on google, but what I found was ...
6
votes
3answers
3k views

Why should the size of the swap partition be double of the RAM size?

Why is it recommended that the swap partition size be double that of the RAM size? Specifically, why would I need to store data stored in the RAM twice??
5
votes
2answers
4k views

Understanding top command in unix

When I run top -c command on my UNIX box I get the output below: top - 03:09:34 up 5 days, 6:14, 1 user, load average: 0.00, 0.00, 0.00 Tasks: 175 total, 1 running, 174 sleeping, 0 stopped, ...
1
vote
1answer
196 views

What are the numbers in parentheses in the names of unix tools? [duplicate]

Possible Duplicate: what does crypt(3) and whatnot mean I'm talking about, e.g. in the git Manual pages, on the git(1) page, See gittutorial(7) to get started, or git-add(1) ...
3
votes
1answer
6k views

How to change user in winSCP?

I'm using winSCP to access Unix computers. How can I change user after I have logged into a Unix server using winSCP? E.g. I have personal account in unix computer A. I can log into this comp using ...
1
vote
3answers
2k views

Modification of files with 777 permissions but not with 755 permissions?

I can modify the files with 777 permissions, but not with 755. I do it by sourcing some sed commands. I find it odd because I can modify the files with even 700 permissions in Vim. Why is it not ...
35
votes
4answers
116k views

What is the .bashrc file?

Unix shells when starting read the .bashrc file and execute commands contained in them. What is this file and what do they execute?
62
votes
12answers
5k views

What command do I need to use to remove a file called `-rf`?

I did something crazy at some point that created a file called -rf on my filesystem. Now I can't figure out how to delete it... I've tried: rm "-rf" rm \-rf These just exit immediately, arrgh! ...
56
votes
8answers
15k views

Why is “Everything is a file” unique to the Unix operating systems?

I often hear people say "Unix's unique philosophy is that it treats everything as a file" or "In Unix, everything is a file". But I've never heard anyone explain why it is unique to Unix. So, why is ...
36
votes
4answers
9k views

What is the origin of the UNIX $ (dollar) prompt?

The UNIX prompt uses a $ symbol to indicate that your input is expected. I was wondering why this symbol was chosen -- if there is a reason. Dollar just seems a little unexpected. A > would have been ...
20
votes
5answers
10k views

How can I trigger a notification when a job/process ends?

The place I work has commands that take a long time to execute. Is there a command/utility that I can use to notify me when the command execution is over? It could be a popup window or maybe a ...
9
votes
3answers
20k views

Copy list of files

I have a list of files separated by spaces in a file list.txt. I'd like to copy them to a new folder. I tried to do: cp `cat list.txt` new_folder but it did not work. How would you do this ? ...
38
votes
3answers
23k views

What does load average mean in unix/linux?

If I run uptime, I get something like this: 10:50:30 up 366 days, 23:27, 1 user, load average: 1.27, 2.06, 1.54 What do those numbers on the end mean? The man page tells me it's "the load ...
25
votes
8answers
10k views

Rename a group of files with one command

If I have a group of files with a .htm extention, how can I rename them all to .html? mv *.htm *.html does not work.
33
votes
3answers
64k views

How can I make chown work recursively?

I've got a directory called pdfs that contains a bunch of sub- and sub-sub-directories. I want to change ownership on all PDF files in all of the subfolders. I just tried this: chown -R ...
19
votes
4answers
46k views

How to gzip multiple files into one gz file?

I have 100 files: cvd1.txt cvd2.txt ... cvd100.txt How to gzip 100 files into one .gz file so that after I gunzip it, I should have cvd1.txt, cvd2.txt ... cvd100.txt separately? Thanks for your ...
18
votes
4answers
14k views

tar – extract discarding directory structure

unzip has a nifty option -j, whereby the directory structure of the archive is discarded, and all files are extracted into the same directory. Is there a way of making tar work in the same way? ...
10
votes
2answers
12k views

How to keep program running after SSH disconnection? [duplicate]

Possible Duplicates: Keep a program running after closing a console, after the program has started How can I use ssh to run a command on a remote Unix machine and exit before the command ...
10
votes
5answers
3k views

What is the official installer for Unix packages on Mac OS?

I'm a bit confused about the installation of standard Unix packages on Mac OS X. For example, I have /usr/bin/svn, which is SVN v.1.4.4, but FinkCommander says svn is not installed. The same holds for ...
9
votes
2answers
6k views

Finding all symbolic and hard links to a file on UNIX

If I have a specific file in a UNIX filesystem, is there a way to use bash to find all links to that file, both symbolic and hard? If I need different commands for each, what are they?
5
votes
3answers
4k views

List all unique extensions for files contained in a directory

I would like to see all the unique extension of files contained in a certain directory. What is the command to do that in bash? One could use find . -type f to get all the files in the current ...
10
votes
3answers
9k views

Bash Man Page: kill <pid> vs kill -9 <pid>

My man page does not document the difference between kill <pid> and kill -9 <pid> Since these do different things why is the -9 not documented in the kill manpage? I thought maybe ...
6
votes
1answer
230 views

Is it possible to 'instantly' create arbitrary files?

I've seen the following trick to create large, empty files somewhat quickly: dd if=/dev/zero of=test.dat bs=1024 count=1024 However, this still takes some time when creating multi-GB files. I ...
15
votes
2answers
4k views

What happens to running processes when I lose a remote connection to a *nix box?

I occasionally lose my remote SSH connection to my VPS. I use screen for long-running processes, but am wondering what happens to the processes I had running aside from those run within a screen ...
8
votes
3answers
16k views

finding L2 cache size in Linux

I wanted to know how to find L2 cache size in Linux... for L1 cache size, I am doing the following pico /proc/cpuinfo what about L2 cache size?
8
votes
1answer
11k views

Console commands to change virtual ttys in Linux and OpenBSD

In Linux one presses Alt-F1, Alt-F2 etc to change virtual ttys. In OpenBSD one shall use Ctrl-Alt-F1 etc instead. My question is if there are console commands for these two operating systems that ...