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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4
votes
2answers
181 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
231 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
1k 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 ...
12
votes
3answers
18k 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
800 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
461 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
2k 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
170 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: ...
35
votes
5answers
4k views

What are the fundamental differences between the mainstream *NIX shells?

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
8k 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 ...
21
votes
2answers
4k 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
791 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 ...
11
votes
7answers
12k 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
3answers
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
751 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
359 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 ...
7
votes
5answers
12k 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
8k 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 ...
22
votes
5answers
31k 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).
5
votes
3answers
305 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
2k 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
2k 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
992 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
92 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
295 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
10k 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?
5
votes
2answers
580 views

modify path globally

Is there a standard for $PATH and the order of things that are supposed to be in there? out of the box Arch Linux doesn't have /usr/local/bin in the $PATH. I want to add it but I'm not sure if there's ...
17
votes
6answers
16k views

Grabbing the extension in a file name

How do I get the file extension from bash? Here's what I tried: filename=`basename $filepath` fileext=${filename##*.} By doing that I can get extension of bz2 from the path /dir/subdir/file.bz2, ...
5
votes
1answer
244 views

Whenever I type some wrong command, my terminal tries to run that command in the background

Something strange started happening to my terminal. Whenever I type some wrong command it tries to run that command in the background. hegeek@colinux: ~# l [9]+ Stopped l thegeek@colinux: ~# ...
2
votes
1answer
491 views

Emacs mode in zsh: M-b M-f etc. show weird symbols

I have set up zsh to use emacs mode. But typing Alt+f or Alt+b inserts weird symbols (accented letters and so on), rather than moving around by word in the shell like it should. Since I don't ever ...
1
vote
3answers
242 views

Directory filenames with sed with whitespaces

I'm working on a script and I'm stuck, even with the help of the google. Here's my code: for FOLDER in `find . -type d | sed "s#^.#$(pwd)#" | sed 's/ /\ /g'` do echo "$FOLDER" done This will ...
7
votes
3answers
7k views

How do I change folder timestamps recursively to the newest file?

I was wondering if anyone knows how to change the timestamps of folders recursively based on the latest timestamp found of the files in that folder. So for example: ...
54
votes
8answers
14k views

How do I delete a file whose name begins with “-” (hyphen a.k.a. dash or minus)?

How do you remove a file whose filename begins with a dash (hyphen or minus) -? I'm ssh'd into a remote OSX server and I have this file in my directory: tohru:~ $ ls -l total 8 -rw-r--r-- 1 me ...
2
votes
3answers
906 views

understanding sudoers

I have a unix script which creates a temporary log file, say tempfl.log. When this file is created it has permission rw-r--r--. There is a line chmod 0440 /etc/sudoers tempfl.log 2>&1 But ...
5
votes
1answer
1k views

Is it possible to use named colors in Zsh beyond ANSI names?

I know there are ways to use ANSI color names in Zsh (such as red), but Zsh supports 256 colors by number. I'm curious if there's any way to refer to the non-ANSI colors by a name? (Without just ...
47
votes
5answers
4k views

Redirecting stdout to a file you don't have write permission on

When you attempt to modify a file without having write permissions on it, you get an error: > touch /tmp/foo && sudo chown root /tmp/foo > echo test > /tmp/foo zsh: permission ...
4
votes
2answers
4k views

change prompt color depending on user or root in zsh

in zsh you can have a %# in your PS1 (or whatever PROMPT variable) which basically means display % if user or display # if root. I'm wondering if there is any way to affect this so that the % or # ...
2
votes
1answer
302 views

vi mode doesn't display correctly on new term

This is a continuation of my previous questions. I currently have the following in ~/.zsh.d/functions.sh function zle-line-init zle-keymap-select { psvar[1]="${${KEYMAP/vicmd/}/(main|viins)/-- ...
18
votes
3answers
29k views

How do I switch from an unknown shell to bash?

I was surprised that I didn't find this question already on the site. So, today $ came up after I logged in as a new user. This was unexpected because my main user's prompt starts with ...
5
votes
2answers
2k views

Does cut support non-white-space to white-space delimeters?

The default delimiter in awk is white-space to non-whitespace change. The default for cut is the tab character. Can I tell cut to use non-white-space to white space delimters? E.g. a: foo bar ...
19
votes
5answers
4k views

Why is echo a shell built in command?

$ which echo echo: shell built-in command. $ which ls /bin/ls $ which cat /bin/cat Why is echo not an independent utility like ls, ps, cat etc? Why is it shell specific? Any good reasons?
4
votes
3answers
9k views

Convert ascii code to hexadecimal in UNIX shell script

I'd like to convert ASCII code (like - or _ or ., etc.) to hexadecimal representation in the Unix shell (without bc command), eg : - => %2d. Any ideas?
11
votes
8answers
389 views

How to access the history on the fly in unix?

for example, if I do a mkdir thisismyfolder912 I remember there is some easier way to switch to thisismyfolder912 than having to do a cd thisismyfolder912 What is that way and how does it work? ...
4
votes
2answers
421 views

Scheduling command/script by specifying the exact second

I'm using bash and wondering how I can execute a command/script at a later specified time, with the accuracy of a second? I read the man page for the at-command, but as far as I could understand it's ...