Questions tagged [unix]

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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158
votes
10answers
145k views

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
27k 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 . drwxr-xr-x ...
20
votes
2answers
11k 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 ...
230
votes
8answers
19k 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.
90
votes
15answers
76k 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 ...
12
votes
3answers
48k 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 computer ...
482
votes
38answers
377k 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 ...
74
votes
5answers
30k views

What's the difference between one-dash and two-dashes for command prompt parameters?

I was wondering why is it that some programs requires their command prompt parameters to have two dashes in front whereas some (most) only require one dash in front? For example most programs look ...
85
votes
3answers
21k views

'less' command clearing screen upon exit - how to switch it off?

How to force the less program to not clear the screen upon exit? I'd like it to behave like git log command: it leaves the recently seen page on screen upon exiting it does not exit the less even ...
36
votes
8answers
41k views

How Unix'y 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 ...
46
votes
2answers
112k 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 ...
111
votes
5answers
34k views

How do I reload .inputrc?

Background I have heard that the readline module is reading ~/.inputrc and that is how it changes the behaviour of keystrokes under programs such as bash. Question How can I reload this after ...
72
votes
13answers
97k views

What commands can I use to reset and clear my terminal?

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 ...
31
votes
1answer
6k 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 ...
20
votes
4answers
104k 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 ...
20
votes
3answers
33k 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, ...
42
votes
8answers
8k 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 ...
3
votes
1answer
3k views

How can the bash shell on Window be completely reset?

I'm new to Unix but interested learn, so started trying to use bash/Ubuntu on Windows. Unfortunately, bash crashed and now bash/Ubuntu seems to be broken as most folders are now missing from the ...
331
votes
7answers
865k 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 someuser:...
170
votes
18answers
212k views

Unix/Linux find and sort by date modified

How can I do a simple find which would order the results by most recently modified? Here is the current find I am using (I am doing a shell escape in PHP, so that is the reasoning for the variables): ...
217
votes
12answers
56k 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 ...
109
votes
3answers
350k views

What is the .bashrc file?

Unix shells when starting read the .bashrc file and execute commands written in it. What is this file and what does it execute?
8
votes
3answers
4k views

Difference between df -k and du -sh

df -k /dev/sda6 25396228 21249088 2836240 89% /export 21G used versus du -sh /export 3.4G /export The 3.4G is correct because we have removed all non essential file but free ...
4
votes
1answer
28k views

How to type commands in PuTTY by creating batch file?

I have created a .bat file which automatically takes the SSH server (Jump Server) access. Now, I have couple of commands which I would like to hit in that window. For an ex. (To take root access) ...
184
votes
3answers
82k views

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

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 ...
130
votes
4answers
77k views

Bash: Spaces in alias name

I am trying to create an aliases in bash. What I want to do is map ls -la to ls -la | more In my .bashrc file this is what I attempted: alias 'ls -la'='ls -la | more' However it does not work ...
89
votes
2answers
51k 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?
22
votes
3answers
10k 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 ...
38
votes
5answers
70k 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? ...
21
votes
8answers
21k views

Best practices to alias the rm command and make it safer

Some time ago I erroneously deleted my home folder because I ran a rm -rf * on the wrong terminal, whose working directory was the home folder! I wish I had an alias for the rm command, but it was ...
15
votes
2answers
19k 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 completes?...
16
votes
4answers
16k views

Unix: Is there a way to “copy” file or directory permissions?

I have two files in a directory. One has correct permissions and the other has not. Is there a way I can "copy" the set of permissions from one file to another?
8
votes
4answers
6k 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 now I ...
9
votes
4answers
2k views

Unix tools: what if a file is named minus something?

I'm always wondering: most GNU/Unix tools take options in the form "minus something", sometimes followed by an argument. What if you got a file named minus something? $ ls -f $ rm -f $ ls -f $ mv -f ...
1
vote
1answer
702 views

Appending new lines to multiple files

I'm trying to append new lines to multiple files with the following command: find -name *.ovpn -exec sh echo "line to append" >> {} \; before doing this, I ran a different command to make sure ...
1
vote
2answers
1k views

How to open files with forward dash in linux

I need to open a file with filename that contains forward slashes. I am wondering how I can do that. I have been searching through Google and I can't seem to find a way. Thanks
87
votes
4answers
146k 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 ...
121
votes
8answers
100k views

How do I configure SSH so it doesn't try all the identity files automatically?

I have been putting my ssh identity files inside my ~/.ssh/ folder. I have probably about 30 files in there. When I connect to servers, I will specify the identity file to use with something like ...
63
votes
11answers
48k views

What is the relationship between Unix, Linux, Ubuntu, Debian and Android?

What is the relationship between Unix, Linux, Ubuntu, and Debian? I suspect they are all Operating Systems that are based upon one another - similar to how Windows is based on DOS. Is my suspicion ...
39
votes
3answers
114k 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 ? ...
43
votes
6answers
24k 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 saw ...
80
votes
6answers
261k 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?
69
votes
4answers
63k views

What does load average mean on 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 average ...
35
votes
6answers
58k views

How to find the 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?
77
votes
8answers
89k views

How can I find the oldest file in a directory tree

I'm looking for a shell one-liner to find the oldest file in a directory tree.
27
votes
4answers
23k views

How to replace part of a text file between markers with another text file?

Say I have a text file like this: # custom content section a b ### BEGIN GENERATED CONTENT c d ### END GENERATED CONTENT I'd like to replace the portion between the GENERATED CONTENT tags with the ...
25
votes
2answers
25k 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$ ...
6
votes
2answers
8k views

Howto interpret SMART-Attributes?

I want to estimate the health and the remaining lifetime of my hard drive using SMART (in my case gsmartcontrol). However I don't know how to interpret the attributes. More specifically: Which ...
18
votes
2answers
14k 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 ...
11
votes
2answers
870 views

How can I list permissions of every component in a file path?

Sometimes it is necessary to determine on which directory in a path access rights are limited. Here is an example: $ ls /sys/kernel/debug/usb/devices ls: cannot access /sys/kernel/debug/usb/devices: ...

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