Bash is the shell used in Ubuntu's command-line interface.

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What is the CVE-2014-6271 bash vulnerability (Shellshock) and how do I fix it?

Recently, there have been news going around regarding "CVE-2014-6271" (See USN-2362-1), which is a vulnerability in Bash. How do I know if I am affected by this, how can I fix it, and why should I ...
114
votes
10answers
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Moving from bash to zsh

I'm considering moving from bash to zsh as I often come across posts praising zsh. I'm an experienced command line user and I'm assuming the basics are pretty much the same, so I'm looking for advice ...
97
votes
8answers
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How do I create a permanent Bash alias?

I would like to create an alias to rm command in order to have a confirmation message after executing this command. So I am creating an alias like this alias rm='rm -i'. But as far as I know this is a ...
91
votes
7answers
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How to get bash or ssh into a running container in background mode?

I want to ssh or bash into a running docker container. Please, see example: $ sudo docker run -d webserver webserver is clean image from ubuntu:14.04 $ sudo docker ps CONTAINER ID IMAGE ...
90
votes
3answers
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How to increment a variable in bash?

How to increment a numeric variable in bash? I tried with var=$var+1 and var=($var+1) but it doesn't work. My variable is a number, but bash think that is a string. My bash version is ...
87
votes
8answers
206k views

How to clear bash history completely?

I want to clear all before command from history of my server. I use history -c it seems all things are cleared but when I ssh to the server,all commands are still there. How can I clear them ...
81
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9answers
16k views

How can I tell what date Ubuntu was installed?

is there a command which will output the date that ubuntu (or any distribution) was installed?
75
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5answers
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Which one is better: using ; or && to execute multiple commands in one line?

In tutorials and how-to's I often see commands combined. For instance, sudo apt-get update && sudo apt-get install pyrenamer There seem to be four possible connectors: &, &&, || ...
75
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5answers
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How to list all variables names and their current values?

Including not only $HOME, $PWD etc but any other you have defined.
73
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6answers
143k views

How can I decode a base64 string from the command line?

I would like to write a bash script to decode a base64 string. For example I type decode QWxhZGRpbjpvcGVuIHNlc2FtZQ== and it prints Aladdin:open sesame and returns to the prompt. So far I have tried ...
70
votes
4answers
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Hide current working directory in terminal

As a default, the terminal prompt shows something like: user@system:/folder1/folder2/folder3/folder4$ the deeper you go into the filesystem, the less space is left for typing in commands. Can I ...
69
votes
4answers
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Why ~/.bash_profile is not getting sourced when opening a terminal?

Problem I have an Ubuntu 11.04 Virtual Machine and I wanted to set up my Java development environment. I did as follows sudo apt-get install openjdk-6-jdk Added the following entries to ...
62
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4answers
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How to see the command attached to a bash alias?

Suppose I have an alias in the bash shell. Is there a simple command to print out what command the alias will run?
62
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3answers
131k views

What is difference between #!/bin/sh and #!/bin/bash?

if I write, #!/bin/bash echo "foo" or #!/bin/sh echo "foo" both yields same. I have seen some scripts starting with #!/bin/sh or #!/bin/bash. Is there any difference between them?
60
votes
10answers
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Why do I need to type `./` before executing a program in the current directory?

While executing a C program, a.out, using the Ubuntu terminal, why do I always need to type ./ before a.out, instead of just writing a.out? Is there solution for this?
59
votes
2answers
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What is the difference between “source” and “.” in bash?

As the question says, what is the difference between executing a script with source command and with . , i.e.: source /some/script and . /some/script
55
votes
5answers
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Running programs in the background from terminal

How do I run a program in the background of a shell, with the ability to close the shell while leaving the program running? Lets say my UI is having problems or for some reason, I need to boot up a ...
55
votes
4answers
102k views

How do I find the version of bash I am running?

(learning bash) I was trying to check the bash version so I typed /bin/bash -v. That outputted a whole lot of text to the screen (contents of .bashrc, and other files sourced from it). Could I have ...
55
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1answer
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'sudo su -' vs 'sudo -i' vs 'sudo /bin/bash' - when does it matter which is used, or does it matter at all?

When I'm doing something that requires root be typed in dozens of times in a row, I prefer to switch my session to a root session. In the various tutorials and instructions I have used on the ...
52
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6answers
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When using && and sudo on the first command, is the second command run as sudo too?

If I run a command. sudo some-command && some-other-command Is the second command being run with sudo previlege also?
50
votes
6answers
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What to do when Ctrl-C won't kill running job?

Sometimes, processes ignore the SIGINT signal sent by Ctrl-C in Bash. For instance, man and vi. Assuming you don't want to google or read the manual on how to exit the running process, is there any ...
50
votes
3answers
5k views

Is #!/bin/sh read by the interpreter?

In bash or sh, I guess anything which starts with # is a comment. But in bash scripts we write: #!/bin/bash And in Python scripts, there is: #!/bin/python Does this mean that # by itself is a ...
49
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5answers
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What does “apt-get install !!” do and how to make it work?

I have seen someone typing apt-get install !! He did that a few times and every time, a different program was installed. It seems like it automatically figured out what is needed next. However, ...
48
votes
3answers
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Bash history search, partial + up-arrow

I have searched, but not found anything on this. I am looking for a functionality in bash, using a terminal. Way back when, I had a user on a debian system, and a friend set me up with a convenient ...
47
votes
5answers
9k views

How can I undo the last cd command?

Is there any way to jump back to the previous working directory after doing a cd to a different directory? My use-case is that I'm traversing a directory structure for a Java project, and I'm ...
45
votes
10answers
262k views

How do I run .sh files in Terminal?

Whenever I open a .sh file, it opens it in gedit instead of the terminal. I can't find any option similar to Right Click → Open With → Other Application... → Terminal. How do I open this file in the ...
44
votes
3answers
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How to grep for tabs without using literal tabs and why does \t not work?

When I search for tabs in a file with (e)grep I use the litteral tab (^v + <tab>). I can not utilize \t as a replacement for tabs in regular expressions. With e.g. sed this expression works very ...
43
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4answers
3k views

When to use () vs. {} in bash?

I'm studying shell scripting with bash and I need to know the difference between (...) and {...}. How does one select between the two when writing a script?
42
votes
14answers
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How can I create a select menu in a shell script?

I'm creating a simple bash script and I want to create a select menu in it, like this: ./script echo "Choose your option:" 1) Option 1 2) Option 2 3) Option 3 4) Quit And according to ...
42
votes
9answers
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How do I restrict my kids' computing time?

Access to our computer (not only to the internet) needs to be restricted for the accounts of my kids (7, 8) until they are old enough to manage this by themselves. Until then we need to be able to ...
42
votes
7answers
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How do I make my terminal display graphical pictures?

This is a quick mockup I copy and pasted together. I imagine this being super cool and useful. Does something like this exist already?
41
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2answers
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What are login and non-login shells?

It is said that settings for non login shell to go into .bashrc file and login shell settings to go into .profile file. What is really meant by login and non-login shells? Please explain without ...
40
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2answers
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How to use variables in 'sed' command?

I try the fallowing code and it does nothing var1=QQ sed -i 's/$var1/ZZ/g' $file However this code replaces QQ with ZZ sed -i 's/QQ/ZZ/g' $file How to use variables in sed?
40
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How can I determine whether a shellscript runs as root or not? [duplicate]

Possible Duplicate: How can a script check if it’s being run as root? This is something I've been curious about. I make a lot of small bash scripts (.sh files) to do tasks that I routinely ...
38
votes
5answers
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Shortcut to clear command line terminal [duplicate]

Is there a shortcut to clear the command line when typing in it instead of keeping backspace pressed for a few long seconds? I ask because I regularly use the Tab key to automatically fill in file ...
38
votes
6answers
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How do I get long command lines to wrap to the next line?

Something I have noticed in Ubuntu for a long time that has been frustrating to me is when I am typing a command at the command line that gets longer (wider) than the terminal width, instead of ...
38
votes
3answers
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How can I shorten my command line (bash) prompt?

Currently it is: michael@Castle2012-Ubuntu-laptop01:~/Dropnot/webs/rails_v3/linker/spec/controllers$ Outside of renaming my machine and directory structure... How could I make it be something ...
38
votes
1answer
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Command to append line to a text file without opening an editor

Assuming i have a line that i want to add to a file without opening an editor. How could i append this line alias list='ls -cl --group-directories-first' to this file config.fish
38
votes
2answers
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Is it possible to make writing to .bash_history immediate?

I often open lots and lots of Terminals [Right now I have 7 open on this workspace] and I often search history with grep to find a command I've just written recently, but I don't want to hunt down the ...
38
votes
1answer
9k views

What's the difference between set, export and env and when should I use each?

Every so often I'll bash out a bash script and it strikes me there are a few ways of setting a variable: key=value env key=value export key=value When you're inside a script or a single command ...
37
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6answers
9k views

Is there a difference between the '&&' and ';' symbols in a standard BASH terminal?

They seem to both signal BASH to commence with another command following the symbols but is there a distinct difference?
37
votes
3answers
127k views

'chmod u+x' versus 'chmod +x'

What is the difference between chmod u+x and just chmod +x? I have seen a ton of tutorials that say to use u+x to make scripts executable. However, the u is not mentioned in the chmod help or ...
36
votes
4answers
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How to navigate long commands faster?

Is there a way speed up Linux CLI navigation when I must enter long commands? I simply use arrows right now, and - if I have a long command it takes some time to get from start of the command to the ...
36
votes
3answers
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BASH script to set environment variables not working

I've written the following script to set some environment variables when needed. #!/bin/sh export BASE=/home/develop/trees echo $BASE export PATH=$PATH:$BASE echo $PATH Below the command and the ...
36
votes
4answers
17k views

How to create script with auto-complete?

When I use program like svn and I type in Gnome Terminal: svn upd and hit Tab it's autocompleted to: svn update Is it possible to do something like that in my custom bash script?
36
votes
6answers
36k views

/etc/profile not being sourced

For 11.04, I did a fresh install of my system. Part of that install was to install rvm, which sticks a rvm.sh in /etc/profile.d/. This doesn't work as /etc/profile (which loads each +r in ...
36
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2answers
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How can I tell if my system was booted as EFI/UEFI or BIOS?

How do I determine whether a particular running Ubuntu system was booted using EFI/UEFI, or BIOS?
36
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2answers
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bashrc or bash_profile?

I know the difference between the two bash login scripts: .bashrc is run only by "non-login" shells. .bash_profile (or .bash_login or .profile) is executed by "login" shells. Does anyone have some ...
35
votes
10answers
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Delete all files except files with the extension pdf in a directory

I have a directory that contains the following: x.pdf y.zip z.mp3 a.pdf I want to delete all files apart from x.pdf and a.pdf. How do I do this from the terminal? There are no subdirectories so no ...
35
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10answers
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How to move multiple files at once to a specific destination directory?

I got a bunch of files in some directory (along with many other files) that I want to move. Luckily, all the files I want to move contain a certain identifier in their names, so I can ls | grep ...