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

learn more… | top users | synonyms

25
votes
2answers
13k views

Unix: How to unsplit in screen

I'm trying to learn how to use screen, in unix so that I don't have to open up several ssh connections and terminal windows just because I want to do more than one thing at the same time on a machine. ...
23
votes
5answers
12k views

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

The place I work at 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 ...
23
votes
1answer
18k views

Is there an equivalent to /dev/null in Windows?

If I want to ignore stdout of a command, I do this on *nix: myprog > /dev/null How do I achieve the same on Windows (in cmd or a batch file)?
23
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 ...
23
votes
0answers
21k 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 . ...
22
votes
7answers
3k views

Is there a standard unix program that returns a range of numbers

Im learning shell scripting from an outdated textbook, and it seems to me like it'd be really usefull to have a program that just returns a string of numbers delimited by spaces something like $ ...
22
votes
2answers
17k views

How to find files with certain text in the Terminal

I'd like to find all files that contain a certain string of text. How would you do that in the Terminal?
22
votes
3answers
50k views

How do I list the groups that a UNIX user is a member of?

With pts m groupname I can list the users in a group. How can I do the opposite - that is, list all the groups that a user is a member of? (I need this to find the name of a group that I know a user ...
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 ...
21
votes
7answers
35k views

Which is more efficient - tar or zip compression? What is the difference between tar and zip?

I'm working in Linux environment and want to know about tar and zip commands. Which is more efficient - tar or zip? I also need to know the differences between the tar and zip commands. Can anyone ...
21
votes
5answers
2k views

Are Linux commands interchangeable with Unix commands?

I find that some commands, for example, ls and pwd, can be used on both Linux and Unix systems. Is it that all Linux commands can be used in the Unix systems, and all Unix commands can be used in ...
21
votes
4answers
53k 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 ...
21
votes
13answers
4k views

Non-Windows, non-Unix-like OS's?

Since most operating systems I've heard of besides Windows seem to derive their heritage from Unix, I've been curious whether any OS's with the following characteristics exist: Not generally ...
21
votes
4answers
24k views

What is effect of CTRL + Z on a unix\Linux application

I was curious and confused that what exactly is the behaviour of CTRl+Z. I know, If a process in running in foreground, and we press ctrl+z, it goes to background. But what exactly happens. Does it ...
21
votes
3answers
21k views

How do you find the parent process of a zombie process?

How do you find the parent process of zombie processes? When the child process is something where the parent is not entirely obvious... Is there some way to list processes in tree format or ...
21
votes
6answers
2k views

What is the general consensus on “Useless use of cat”?

When I pipe multiple unix commands such as grep, sed, tr etc. I tend to specify the input file that is being processed using cat. So something like cat file | grep ... | awk ... | sed ... . But ...
21
votes
2answers
52k views

Command: sudo su -

I understand what su - does logs you into root with the root environment (as opposed to su which logs you into root with your environment) And I understand what sudo does you are root for one ...
21
votes
4answers
8k views

which/whereis differences

What's the difference between which and whereis ?
21
votes
2answers
49k views

How to UNIX sort by one column only?

I know that the -k option for the Unix sort allow us to sort by a specific column and all of the following. For instance, given the input file: 2 3 2 2 1 2 2 1 1 1 Using sort -n -k 1, I get an ...
21
votes
3answers
9k views

Does rm -f follow symbolic links?

I have a directory like this: $ ls -l total 899166 drwxr-xr-x 12 me scicomp 324 Jan 24 13:47 data -rw-r--r-- 1 me scicomp 84188 Jan 24 13:47 lod-thin-1.000000-0.010000-0.030000.rda ...
20
votes
2answers
7k views

Can the output of one command be piped to two other commands?

How can I pipe the output of one command to the input of two other commands simultaneously?
20
votes
6answers
14k views

On Linux/Unix, does .tar.gz versus .zip matter?

Cross-platform programs are sometimes distributed as .tar.gz for the Unix version and .zip for the Windows version. This makes sense when the contents of each must be different. If, however, the ...
20
votes
2answers
11k views

How do I interpret the results of the `ls -l` command?

I want to learn about the meaning of values for example first line; drwxr-xr-x 2 ataka root 4096 2008-11-04 16:58 ataka is ataka here the owner of directory ? kioutsovkm@orkide:/users/lnxsrv2/ee$ ...
20
votes
2answers
35k 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
17k views

How do file permissions apply to symlinks?

Let's say you have this structure: + directory -- file1 -- file2 -- file3 -> /tmp/file3 file3 is a link to another file3 somewhere else on the system. Now let's say I chmod 777 the directory ...
20
votes
4answers
32k views

What's the difference between .profile and .bash_profile, and when do you configure which? (Mac) [duplicate]

Possible Duplicate: Difference between .bashrc and .bash_profile What's the difference between .profile and .bash_profile, and when do you configure which? I.e if I configure the ...
19
votes
9answers
10k views

Is there a way to display a countdown or stopwatch timer in a terminal?

How can I display a real-time countdown timer on the Linux terminal? Is there an existing app or, even better, a one liner to do this?
19
votes
5answers
16k 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? ...
19
votes
2answers
33k views

How do I gunzip to a different destination directory?

How do I gunzip to a destination directory other than the current one? This did not work: gunzip *.gz /putthemhere/
19
votes
3answers
8k views

Random password generator: many, in columns, on command line, in Linux

A while back, I came across a random password generator for the command line that displayed a grid of "memorable" passwords. Output was something like this: adam@host:~$ CantRememberThisCommand ...
18
votes
4answers
670 views

Getting rid of a file called “-d” [duplicate]

Possible Duplicates: How do I delete a file named "-p" from bash? How to delete file with this name on linux: -]???????q Removing "-rf" file in Unix I've ...
18
votes
9answers
10k 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 ...
18
votes
4answers
6k views

Powershell equivalent to unix `which` command?

Does powershell have an equivalent to the which command found in most (if not all) unix shells? There are a number of times I'd like to know the location of something I'm running from the command ...
18
votes
2answers
11k views

Exclude hidden files when searching with Unix/Linux find?

What options do I need to use with find to exclude hidden files?
17
votes
5answers
3k views

Does dual-booting an OS require a dual-core processor?

My friend claims that dual booting, using two different OSes, requires a multi-core or multi-threaded processor. Is this true? And if I install additional OSes, will my computer slow down any?
17
votes
9answers
14k views

What's the difference between the commands “su -s” and “sudo -s”?

What is the difference between the two super user commands, su -s and sudo -s? They both give a shell with access to the superuser account.
17
votes
3answers
57k views

How can I concatenate two files in Unix?

How can I create a new file "new.txt" that is a concatenation of "file1.txt" and "file2.txt" in Unix?
17
votes
4answers
28k views

List the current folder folder's sizes with the terminal?

I want a list of the folders from the current directory or one that I specify with their size. I have tried with du but I only get the size of the directories I specify (du . ./f1), and ls doesn't ...
17
votes
4answers
8k views

How are PID's generated?

On *nix, PIDs are unique identifiers for running processes. How are PID's generated? Is it just an integer which gets incremented or a more complex structure such as a list? How do they get recycled? ...
17
votes
2answers
533 views

What does the 1 in ls(1) refer to? [duplicate]

Possible Duplicate: What do the parentheses and number after a Linux command or C function mean? I see that many utilities have a number in brackets after their name, for example ls(1) or ...
17
votes
2answers
8k views

Linux 'man' command: How do I search for a word/phrase and cycle through?

When looking for a certain word or phrase in the man page of linux command, one can type '/' followed by the word/phrase to search for it. What I'd like to be able to do is to search for the next ...
16
votes
3answers
1k views

How can I remove a file or directory called “\”?

I'm using terminal on a Ubuntu machine and there is a file that I would like to delete. The file's name is \ (just a backslash). Now usually I would just do rm filename However if I do rm \ then ...
16
votes
3answers
9k views

Safely get rid of “You have new mail in /var/mail” on a Mac?

I was messing around with sendmail in Rails a year ago and have had this message popping up in the terminal after every command ever since: You have new mail in /var/mail/Lance How do I properly ...
16
votes
4answers
10k views

How do I get the mx records for a domain from *nix command line?

What is the best way to lookup MX records for a domain from the command line?
16
votes
2answers
11k views

Counting total number of matches with grep instead of just how many lines match

Does grep offer a way to count the total number of matches it makes? The -c option only returns the number of lines that matched the regex, but in this case I have multiple matches per line.
16
votes
2answers
1k views

Is there a git-like file system?

Git stores content uniquely in its repo based on the calculated hash of any file. Thus, if my directory has two copies of the same file somewhere inside it, git will only actually store it once. I ...
16
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 ...
15
votes
2answers
9k views

How does one switch between windows on VIM?

I'm using both Vim and MacVim (or well, trying to). I installed the Tagbar plugin but find it impossible to switch to the actual Tagbar window to make my selection. I've been reading loads about ...
15
votes
5answers
8k views

Mac OS X: at command not working

I am going to schedule a job by using at command. Here I tried the following command: $ at now + 1 minute echo 'Test at command' <EOD> I saw the job is scheduled by using at -l. However, I ...
15
votes
3answers
19k views

unix copy a directory

How can I copy a directory structure dir1 to dir2 ? (with all the subdirectories) in unix using the terminal window