The shell is unix's command-line interface. You can type commands in a shell interactively, or write scripts to automate tasks. Use this tag for questions applying to /bin/sh and most compatible shells (ash, bash, ksh, zsh, …).

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5answers
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Does $SHELL store the path to the default shell in Linux?

My administrator says that my default shell is set to bash, but $ echo $SHELL /bin/csh $ Is the default shell related to the SHELL variable at all? Is not, what is the variable used for?
537
votes
3answers
111k views

What is the exact difference between a 'terminal', a 'shell', a 'tty' and a 'console'?

I think these terms almost refer to the same thing, when used loosely: terminal shell tty console What exactly does each of these terms refer to?
21
votes
3answers
5k views

ls command: what does the first line mean?

When I do ls -l I get this: calico@A000505:~/Documentos$ ls -l total 2020 -rwxr-xr-x 1 calico calico 8559 2010-11-16 11:12 a.out -rwxrw-rw- 1 smt smt 2050138 2010-10-14 10:40 Java2.pdf ...
7
votes
1answer
775 views

What steps does the system go through when handling an SSH connection?

What steps does the system go through when handling an SSH connection? We try to log in via ssh sshd starts pam and pam module to authenticate us Depending on pam configuration, we need to provide ...
9
votes
1answer
880 views

How do I redirect output to cd?

Is it possible to redirect a command's output to cd? For example, I searched for a directory using locate and got the path to it. Now, instead of writing a cd path, can I redirect the locate output to ...
18
votes
1answer
3k views

Aliases vs functions vs scripts

This site says, "Shell functions are faster [than aliases]. Aliases are looked up after functions and thus resolving is slower. While aliases are easier to understand, shell functions are preferred ...
6
votes
2answers
303 views

How is a graphical application started from a bash session connected to that bash session?

When I start a graphical application from a terminal running bash, that application is somehow connected to that bash session. For example, when the applications dumps some text it will appear in the ...
188
votes
2answers
45k views

Difference between nohup, disown and &

What is the difference between $ nohup foo and $ foo & and $ foo & $ disown
1
vote
1answer
528 views

CH3MNAS Fun Plug and NZBget. Cannot launch NzbGet 0.7, word unexpected

I have un-tarred the nzbget0.70 debug version and have put it in the /ffp/bin dir. and I have a config file in the /ffp/etc/ dir but when I try to run it, I get the following: ...
30
votes
3answers
9k views

How to pass parameters to an alias?

For bash script, I can use "$@" to access arguments. What's the equivalent when I use an alias?
3
votes
2answers
813 views

Forcing emacs to run with `-nw` when called from terminal

note: This question might have been asked before ( I think I saw it somewhere), but a quick search did not reveal anything. I would like to tell the difference when a command is run from a shell. ...
6
votes
3answers
956 views

Deleting lots of files

I accidentally created 8 million files and every time I'm trying to delete them the server almost dies because of the rm process eating all disk IO (the server is remote without console). Should ...
5
votes
2answers
4k views

How do I delete all files with a given name in all subdirectories?

I want to delete all files with a given name in all the subdirectories of my home directory. I tried: rm -r file in my home directory, but it didn't work because that file doesn't exist in that ...
4
votes
2answers
3k views

Why am I getting a syntax error with my Shell arithmetic?

I have a problem with a linux shell script (sh). I'm trying to write a script that calculates combinations, but I think I get overflows when trying to calculate faculties. So, I'm trying another ...
2
votes
0answers
320 views

How can I check which shell I am currently using? [duplicate]

Possible Duplicate: How to test what shell I am using in a terminal? An echo $SHELL will only display the value of the SHELL variable which would indicate the default shell on the system. ...
4
votes
3answers
2k views

Make terminal text color different when in ssh session

Is there a way to make my terminal (konsole) display different text colors when I'm in an ssh session WITHOUT modifying the remote host's color configuration? Like, maybe automatically switching to a ...
13
votes
1answer
7k views

touch: cannot touch `foo': No such file or directory

What could cause touch to fail with this error message? touch: cannot touch `foo': No such file or directory Note that an error due to incorrect permissions looks different: touch: cannot touch ...
20
votes
1answer
6k views

Difference between environment variables and exported environment variables in bash

Bash seems to differentiate between variables which have been exported and those which have not. example: $ FOO=BAR $ env | grep FOO $ set | grep FOO FOO=BAR set sees the variable but env does ...
4
votes
2answers
195 views

How can I display the time when a command was executed in my bash prompt?

Currently my bash prompt looks like this $ echo $PS1 # \[\e[34m\][\t]\[\e[0m\] \[\e]0;\w\a\]\[\e[34m\]\u@\h: \[\e[34m\]\w\[\e[0m\]\n$ $ The problem is that \t will only display the time when the ...
5
votes
4answers
235 views

How could I simplify this command to only use awk?

awk '/user/ {print $1 }' /etc/userdomains | sed 's/://' the format of /etc/userdomains is domain.tld: user otherdomain.tld: otheruser
8
votes
3answers
2k views

How do I take a list and remove it from a file?

I have a long list of domain names that I need to remove from /etc/remotedomains. They're probably not in any particular order in the file. Each domain is on one line. How could I iterate through the ...
14
votes
3answers
26k views

Grabbing the first [x] characters for a string from a pipe

If I have really long output from a command (single line) but I know I only want the first [x] (let's say 8) characters of the output, what's the easiest way to get that? There aren't any delimiters.
5
votes
2answers
832 views

How to make sure that I use the latest version of bash?

I just setup bash v4.1.0 on my machine. The old version is under /bin/bash. Is there a way to use the newer version of bash without replacing the old one from /bin? I want the newer version to be ...
4
votes
1answer
547 views

What are the new features available to bash 4?

I was using bash3 up to now, and just got a copy of the latest version $ ./bash --version GNU bash, version 4.1.0(1)-release (i686-pc-linux-gnu) Copyright (C) 2009 Free Software Foundation, Inc. ...
14
votes
4answers
3k views

Share aliases and PATH setting between zsh and bash

The shell that I normally use is zsh. I have several aliases to enable color in some programs such as ls and grep. I've also set my custom path so that I can execute programs in non-standard place ...
5
votes
3answers
172 views

How do I remove every file that has x in its title?

I have a lot of directory where there are hundreds of files. In every directory there are pairs of my_file-01.jpg and my_file-€01.jpg I want to remove every file that contains € sign in its title: ...
36
votes
5answers
4k views

What are the fundamental differences between the mainstream *NIX shells? [closed]

What are the fundamental differences between the mainstream *NIX shells and what scenarios might prompt you to use one over the other? I understand that some of it probably comes down to user ...
8
votes
2answers
10k views

Remove end of line characters from stdout? Multiple lines into a single line

I have a script which outputs the following text. This is the output from a Netopia 2210-02 ADSL2 modem. ADSL Line State: Up ADSL Startup Attempts: 1 ADSL Modulation: DMT ADSL Data ...
23
votes
2answers
5k views

What is the bash shortcut to change to the previous directory?

Sadly, I only learned about this last year by stumbling upon it randomly on the internet. I use it so infrequently that I always forget what it is by the time I need it again. How do you change to ...
4
votes
3answers
1k views

renaming files without the **rename** command

I have a directory of files, Measurements Panama 2009-03-22 Session1.xml Measurements Panama 2009-03-22 Session2.xml Measurements Panama 2009-03-22 Session3.xml Measurements Panama 2009-03-22 ...
7
votes
6answers
1k views

How can I reproduce commands run on one machine on another machine?

I would like to install some software on a linux-machine that I have run in VirtualBox. Then I would like to do the same thing on a linux-VPS. I think that I can save all commands that I run using ...
12
votes
7answers
14k views

grep and tail -f?

Is it possible to do a tail -f (or similar) on a file, and grep it at the same time? I wouldn't mind other commands just looking for that kind of behavior.
18
votes
4answers
2k views

How to know the “level” of shells I am in?

If I open a terminal like xterm I will have a shell. Then if I use ssh or zsh I will have another "level" of shell. Is there a way to know how many times I have to Ctrl+D or type exit to exit all of ...
4
votes
2answers
796 views

RS232 chat. Simplest way?

I'm working in a project in which I will have to deal with serial communications. For testing, I want make to 2 computers speak to each other (with my interaction) via RS232. Will the next thing ...
1
vote
1answer
371 views

error using “du” command

I am on the university machine trying to estimate the disk usage I have on my space I do du -csh ./ from the begining of my account, but an error is given that ./Yesterday/Yesterday is not a ...
8
votes
5answers
16k views

how do I add newlines between lines printed on the command line?

Mail logs are incredibly difficult to read... how could I ouput a blank line between each line printed on the command line. For example say, i'm grep-ing the log. That way multiple wrapped lines ...
4
votes
1answer
1k views

Read space as input in shell script [duplicate]

How can I give space " " as input in shell script ? Ex : echo " Enter date for grep... Ex: Oct 6 [***Double space is important for single date***] (or) Oct 12 " read mdate echo $mdate I get the ...
18
votes
4answers
9k views

Save complete GNU screen session state

Is it possible to persist the "state" of a GNU screen window (or just a standard shell) so that I can reload everything after a reboot: The number of opened shells The name of each shell The current ...
37
votes
7answers
44k views

How do I convert an epoch timestamp to a human readable format on the cli?

How do I convert an epoch timestamp to a human readable format on the cli? I think there's a way to do it with date but the syntax eludes me (other ways welcome).
6
votes
3answers
321 views

Correct textual name for <<

I've just come across the << command, used like so: cat > outfile.txt <<EOF Multi-line content that will be written to outfile.txt EOF Now, I've no idea what this is called, but I'd ...
6
votes
7answers
2k views

Is it bad practice to set root's shell to something other than the default?

Once a friend of mine (who is an experienced Unix/Linux user) told me that setting root's shell to something other than sh (i.e bash or zsh) might create problems, because some script might assume ...
3
votes
5answers
3k views

how to pass the result of `find` as a list of files?

The situation is, I have an MP3 player mpg321 that accepts a list of files as argument. I keep my music in a directory named "music", in which there are a few more directories. I just want to play all ...
6
votes
1answer
3k views

how to view a directory's permission

What is the command with which you can directly view the permission bits of a directory?
4
votes
3answers
1k views

`$XAUTHORITY` appears from 'nowhere' on su+tmux

When I switched from su+bash to su+tmux+zsh I noticed that I get $XAUTHORITY variable defined as /root/.xauthXXXXXX where XXXXXX are 6 random alphanumeric characters. With previous configuration X ...
1
vote
1answer
93 views

how to convert ^I character

I have a text file like this: info Some info here In which when I use cat -A display this: info^I Some info here How do I edit this so I'll get something like this instead: ...
1
vote
2answers
319 views

Problematic build script with quotes

Hi I'm trying to create a build script that executes these commands: cd libiconv ../../src/libiconv/configure --prefix=/home/ruben/mingw64/build/gcc-libs \ ...
0
votes
0answers
326 views

bash: recall command by typing some characters of it [duplicate]

Possible Duplicate: best way to search my shell's history In MSDOS I have the option to start typing some characters of a previous command and then pressing F8 it will search the ...
2
votes
2answers
1k views

Extending history search in zsh

How to extend Ctrl+R search in zsh? It cannot find entry despite it is in history file. Edit: My .zshrc: setopt AUTO_CD setopt CORRECT_ALL setopt EXTENDED_GLOB # History SAVEHIST=10000 ...
16
votes
9answers
11k views

Tool in UNIX to subtract dates

Is there any tool in Solaris UNIX (so no GNU tool available) to subtract dates? I know that in Linux we have gawk that can subtract one date from another. But in Solaris the maximum we have is nawk ...
5
votes
2answers
1k views

dash compatibility to bash

Wikipedia says that dash executes faster than bash. My question is, if I set /bin/sh to dash, will all scripts that use /bin/sh in their shebang line that was intended for bash work under dash?