Questions about bash only, as opposed to other Bourne/POSIX shells. For all Bourne/POSIX-style shells, use the /shell tag instead.

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12
votes
2answers
26k views

How to check if there are no parameters provided to a command?

How do you check if $* is empty? In other words, how to check if there were no arguments provided to a command?
10
votes
1answer
457 views

How to output string completions to stdout?

Some of the git commands have many options, and it would often be useful to search through them for the one I need - I was just looking for the option which controls the TAB width in git-gui, but ...
42
votes
2answers
20k views

Awesome symbols and characters in a bash prompt

I just ran across a screenshot of someone's terminal: Is there a list of all of the characters which can be used in a Bash prompt, or can someone get me the character for the star and the right ...
7
votes
1answer
766 views

Screen cuts off beginning of long command when accessed through bash history

I'm using the default versions of bash and screen in OS X Lion. When I'm in a screen session and I scroll back through the bash history and I come to a command that is long enough to wrap. I might ...
6
votes
2answers
260 views

Output of which command used for input to cd

I would like to take the output of a which command, and cd to the parent directory. For example, say I have the following: which someprogram With output: /home/me/somedirectory/someprogram And I ...
0
votes
1answer
690 views

source .bashrc command doesn't work

I installed TinyOS on RedHat for academic purposes. Now I can't log in to the system. I logged in in single user mode. Then I tried to log in. I couldn't login as any user. I couldn't start the X ...
0
votes
1answer
8k views

Different ways of using expr command [closed]

I'm trying to learn the bash expr command inside and out. What are some of the most basic to the most creative/tricky/unexpected ways to use the expr command? Small, manageable examples are great.
10
votes
4answers
16k views

Grep: how to add an “OR” condition?

I am a total regex newbie. I find it confusing and I avoid it like the plague (wanna take some guesses as to why I'm not good at it?). But I suspect it might be the solution to my question. Which ...
3
votes
3answers
1k views

Implementing rollback in bash

I have a script that is composed of staged operations which work mostly in a start/stop/status manner. The issue I have is that when starting, each of the operations can fail and I need to do a safe ...
6
votes
2answers
2k views

Pasting from clipboard to vi-enabled zsh or bash shell

I'd like to be able to paste from the system clipboard (or text selection) into my "vi-like" shell prompt using the keyboard. I normally use zsh and sometimes bash. In both cases, I have the shell set ...
3
votes
1answer
843 views

Avoid a trailing slash in bash when completing a directory name (like zsh)

I'm on a Mac and the cp and mv commands are killing me due to them copying the contents of a directory if a trailing slash is present. It has bitten me more than once when I use tab completion to ...
4
votes
2answers
91 views

If ^a^b replaces “a” once in the last command, what do I use to replace all occurrences of “a”?

In bash, if I run this command: echo aaaaaaa I get aaaaaaa (duh) But then if I type in ^a^b I end up with baaaaaa What would I type to end up with bbbbbbb ?
2
votes
2answers
381 views

How do I prevent a script from terminating when the shell exits?

In particular, I created a script to start Firefox which I double-click and choose 'Run in terminal,' but when the shell exits Firefox is killed immediately. How do I prevent this from happening?
7
votes
3answers
3k views

Why a long delay after command not found?

Often when I mistype a command such as ls (e.g. I hit ENTER before I type 's') there is a long (~2s) delay after the terminal displays: bash: l: command not found... I can understand the reasons ...
3
votes
2answers
275 views

Bash - file, arrays and output

I have a file that contains employees names, departments and the cities the employee is in, something like: John IT Chicago Joshua accounting New York Marcy CEO Los Angeles ... I have to transform ...
9
votes
1answer
7k views

How to automatically record all your terminal sessions with script utility

What I want to achieve is be able to record my terminal sessions to file automatically whenever I use Yakuake/Konsole. It's easy to achieve if at the start of my session I do: script -f ...
0
votes
1answer
257 views

Is there more, less, or equal overhead for elisp, as for a bash script, to call awk, ps, etc?

Hopefully the question explains itself well enough. I'm referring to exta time and system resources involved for one vs. the other... I tend to think it would be the same, but I want to go beyond just ...
2
votes
3answers
939 views

How to cut the output to only gather the filename and get-parameter?

I have multiple files with multiple links that are formatted like this: <a href="http://example.com/fnord.layername.html?parameter=FOO-_-BAR-_-FNORD" class="poit"> <img ... /> ...
5
votes
2answers
6k views

Looking for a Java class in a set of JARs with find, unzip, grep

I was trying to find the JAR containing a Java Class. JARs are in zip format. My first attempt was: $ find -name "*3.0.6.RELEASE.jar" | xargs -l1 unzip -l \ | grep stereotype.Controller ...
4
votes
5answers
4k views

How to set an alias for a specific file or directory?

There are several files I work with often. For instance some configuration files or log files. Let's say the Apache log file. I often want to tail or grep it. Instead of writing: tail -50 ...
9
votes
2answers
2k views

Bash is not fully functional for a new user

I just created a new user on my system using useradd -d /home/users/john -m john (Using Ubuntu 11.04). This worked fine, but when I changed to john, my bash is not fully functional. That is, it has no ...
8
votes
3answers
3k views

What does : ${param:=value} mean?

I read the following in A User's Guide to the Z-Shell: A synonym for ‘true’ is ‘:’; it’s often used in this form to give arguments which have side effects but which shouldn’t be used — ...
1
vote
2answers
1k views

Running any kind of login script when sh is linked to bash

My problem: My web host offers ssh to their shared server. I want to set up a couple of aliases and such, so I'm trying to get a login script of any flavor to run. If my shell was plain bash, I would ...
4
votes
0answers
172 views

How to preserve bash history in multiple terminal windows [duplicate]

Possible Duplicate: Preserve bash history in multiple terminal windows While working, usually I have multiple terminal windows open (or tabs). I use konsole, but it could be few ssh sesions ...
5
votes
2answers
3k views

watch command alias expansion

If a run the watch command containing an alias, it will not expand the alias. I have tried both with single quote and double quotes, in fact given the following alias: # alias ll alias ll='ls -l ...
2
votes
3answers
2k views

Trouble getting awk output in for loop

I'm trying to create a script that will check a website for a word. I have a few to check so I'm trying to input them via another file. The file is called "testurls". In the file I list the keyword ...
7
votes
2answers
352 views

Why does 'for anytext; do' loop four times?

Is this a bug or a feature? It seems to happen for unquoted alphanumerics. Running GNU bash, version 4.1.5 for alpha01234; do echo $((++i)); done output: 1 2 3 4
31
votes
4answers
87k views

count number of lines, bash grep

Hello I am grepping results to file, and then doing cat to show its content on the screen, I want to know how many lines of results I have in my results file and the += it to some counter. What will ...
7
votes
2answers
1k views

Difference between alias in zsh and alias in bash

I have searched around but could not find anything conclusive. Is there a difference between the alias command in zsh and the alias command in bash? If not, does it mean I can share a set of aliases ...
2
votes
1answer
373 views

Populate PS1 asynchronously

I have a few git svn related functions that see if I have to pull/push from/to the repository. My problem is that the functions I've written to gather this information are too slow. I'd like to make ...
2
votes
5answers
760 views

How to find out if PWD contains spaces or non-English letters?

I created an environment variable: WD=`pwd` How can I check if it contains spaces or non-English letters?
1
vote
2answers
947 views

How can I make bash more readable? [closed]

As a linux user, I spend a lot of time mucking about in bash. I've always been a bit frustrated by how poor the readability is. Today this annoyed me enough to spur me into action. My immediate ...
23
votes
6answers
6k views

How do I close a terminal without saving the history?

More than once I've accidentally run a number of commands and polluted my bash history. How do I close my terminal without saving my bash history? I'm using Fedora.
2
votes
1answer
3k views

Create alias to change directory and list contents

I want to change the behavior of the cd command so that it changes to a directory and lists the files in that directory, but I can't seem to get it to work. I have tried the following with no ...
2
votes
2answers
1k views

How do I echo a command and include line returns?

I am writing a bash script, and on a condition I'd like to output ps aux --sort -rss However, when I write : echo `ps aux --sort -rss` everything is on one huge line. How do I run it so it outputs ...
1
vote
2answers
107 views

Narrow characters

It would be awesome to modify spark to print narrow characters in for example Gnome Terminal. Is this at all possible with Bash / Python?
3
votes
2answers
3k views

How to fix bash looking for a program in the wrong dir (Issues setting up NPM on Ubuntu 11.10)

This time I ran the "trusting" install script curl http://npmjs.org/install.sh | sudo sh from the dir /. $ which npm /usr/local/bin/npm $ npm bash: /home/steven/local/bin/npm: No such file or ...
-1
votes
3answers
2k views

printf white space character in bash script

How can the white space character be escaped in printf for the purpose of this script that currently runs in a Cygwin client? The line containing the whitespace (which by itself works from the command ...
3
votes
1answer
175 views

Why does this variable have no value even though it is set in .bashrc?

If I append this: hi=11 export hi to the .bashrc and then I su to this user with: su - bela then I: echo $hi 11 Then it's working, the "hi" variable has the value of "11". But. When I: ...
16
votes
2answers
5k views

How to execute consecutive commands from history?

Suppose I want to execute a sequence of four commands that I have executed before. If the first one is 432 in the command-history, then I could do: $ !432; !433; !434; !435 I'm curious, is there a ...
1
vote
2answers
4k views

Why does adding a colon break this grep pattern?

I executed a search with grep, but it doesn't work like I expected it to. I have the following lines in a file: blacklists/redirector/domains:needyoutube.com ...
12
votes
3answers
14k views

Confusing use of && and || operators

I was skimming through an /etc/rc.d/init.d/sendmail file (I know this is hardly ever used, but I'm studying for an exam), and I've become a bit confused about the && and the || operators. ...
2
votes
1answer
1k views

find command with -execdir not reading flags?

I am trying to locate all .jpg picture files in my current directory and sub-directories and move them to another directory. I want the source files to overwrite the destination files, but that is ...
15
votes
2answers
1k views

.bashrc overwritten but still sourced — how can it be recovered?

Usually when I find a command I want to alias, I echo it to my .bashrc like so: [up button pressed to last command, then line edited so that it reads] $echo "command-i-just-did" >> ~/.bashrc ...
13
votes
8answers
10k views

How to print the longest line in a file?

I'm looking for the simplest method to print the longest line in a file. I did some googling and surprisingly couldn't seem to find an answer. I frequently print the length of the longest line in a ...
9
votes
3answers
9k views

Invert boolean variable

I want to try simple script flag=false while !$flag do read x if [ "$x" -eq "true" ] then flag=true fi echo "${x} : ${flag}" done But when i run it, if i type true, i will see ...
2
votes
1answer
584 views

What are the dangers with using “--assume-yes” with apt-get?

While making some improvements to my .bashrc file, I noticed a frequently used alias: alias install='sudo apt-get -y install' I wasn't familiar with the -y (aka --assume-yes or --yes) option with ...
2
votes
4answers
312 views

Generate lists of page numbers for 2-up duplex printing: 2,3,… and 1,4,…

How can I generate the following increments? 2,3,6,7,10,11,14,15,18,19,22,23,26,27,30,31,34,35,38,39,42,43,46,47,...,135 and ...
11
votes
1answer
4k views

Terminal autocomplete: cycle through suggestions

I had this on my Ubuntu setup and since I switched to Fedora I want to set it and I forgot how... The idea is simple : I don't want the terminal to show me suggestions when I double tab, instead I ...
2
votes
2answers
432 views

add “check if fetchmail is running” to this script

while ! postqueue -p | grep -q empty; do sleep 1 done killall wvdial this script checks if my mail queue is empty, then disconnects my modem. now i would like to add also a checking to fetchmail ...