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Questions tagged [bash]

Questions specific to GNU’s Bourne Again SHell, as opposed to other Bourne/POSIX shells. For questions about Unix shells in general, use the /shell tag instead.

1
vote
5answers
3k views

Debian sed: can't read

I'm trying to run a command to remove require_once from php files from here (code below), but I am getting the error: sed: can't read -: No such file or directory I am in the correct folder; what'...
6
votes
2answers
358 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 ...
24
votes
1answer
60k views

In Bash, are if [ -z “$1” ] and if [ “$1” = “” ] the same?

In Bash shell scripting, what is the difference (if any) between the following two statements?     1.) if [ -z "$1" ]     2.) if [ "$1" = "" ] I have found ...
4
votes
2answers
3k views

How to write a script to execute files in multiple directories

How do I write a script to execute the files in multiple directories? The problem is this: I have many directories, and each has a data file to be read and analyzed by a python script (say, a.py). I ...
4
votes
1answer
138 views

What is this construct in bash? mycommand(){dosomething;}

I actually found following one-liner on commandfu.com: cmdfu(){ curl "http://www.commandlinefu.com/commands/matching/$@/$(echo -n $@ | openssl base64)/plaintext"; } I have not come across a similar ...
90
votes
5answers
109k views

Understanding the exclamation mark (!) in bash

I used history | less to get the lines of previous commands and from the numbers on the left hand side I found the line I wanted repeated (eg. 22) and did !22 at the command prompt and it worked -...
4
votes
2answers
717 views

How does file descriptor re-assigment work?

In a way this question is a extension of another question. In bash you can do pretty neat stuff with file descriptors. Like { command > /dev/null } 2>&1 | grep filter; to grep on stderr ...
2
votes
0answers
361 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. But I ...
4
votes
4answers
5k views

Applying a regex to stdin

In programing we often see the use of Regular Expressions. One of the most common forms is: newText = text.replace( /regex/, 'replacementString' ) If stdin is text and stdout is newText, what would ...
38
votes
7answers
58k views

Using xargs with input from a file

Say I have a file with the following bob john sue Now these directly corrospond to (in this case) URL pattern such as http://example.com/persons/bob.tar, john.tar, sue.tar. I would like to take ...
12
votes
2answers
85k views

./executable: cannot execute binary file

I have a script that works well when I ssh to the server to execute it myself, but has problems when Hudson, a continuous integration server, runs it. I am automating tests on an embedded linux ...
4
votes
1answer
1k views

Is “export” needed when setting HISTIGNORE in bashrc files?

As I understand it, exporting an environment variable makes it available to any processes spawned from the current one. But the only processes that will be interested in the HISTIGNORE variable (and ...
5
votes
2answers
2k views

Expand KDE activities concept to the shell

Sometimes, I use KDE, and one of the things that I like the most in KDE 4 is the activity concept. At work, it is very useful because I often work on several different projects during one day. ...
50
votes
9answers
24k views

How to print only defined variables (shell and/or environment variables) in bash

The bash builtin command set, if invoked without arguments, will print all shell and environment variables, but also all defined functions. This makes the output unusable for humans and difficult to ...
2
votes
1answer
197 views

Stop cron script from destroying my mirrorlist with invalid data

I have to following cron script that runs daily. As you should be able to see from the code, it outputs the results from reflector to /etc/pacman.d/mirrorlist. $ cat /etc/cron.daily/update-mirrorlist ...
252
votes
4answers
57k views

What does “rc” in .bashrc stand for?

Is it "resource configuration", by any chance?
6
votes
2answers
320 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
2answers
2k 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 ...
5
votes
2answers
3k 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. ...
24
votes
4answers
8k 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 (...
9
votes
5answers
1k views

How do you recall the last (n-th?) passed argument of the previous command you used with bash?

Often times I issue different commands on the same file. For example: $ youtube-dl aB54c4p0eo #I made this video id up on the spot $ mv aB54c4p0eo.flv kittens.flv $ vlc kittens.flv $ rm kittens.flv ...
5
votes
1answer
3k views

How to get a persistent “history”-file even after a non-clean shutdown?

I am trying Ubuntu Server 10.10 in VirtualBox. I like that the commands I run is saved in a "history"-file that can be shown with the history command. But if I just turn off VirtualBox without the ...
70
votes
3answers
26k 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 ...
5
votes
2answers
3k views

How similar is Apple's terminal.app to a bash terminal on Linux?

I know that Apple's Terminal.app provides a bash shell. Are there any differences between this and a bash on Linux?
1
vote
3answers
264 views

Is it possible to know when you're at the first bash prompt of a terminal?

This is sort of a contiunation of my last question: printing saving the last bash input command Now I want to know if it's possible to know when you're at the first bash prompt of a terminal. So I'm ...
6
votes
1answer
3k views

Printing (saving) the last bash input command

How can I get the last executed command from bash? I know that !!:p prints the last command, but it seems I can't use that anywhere except the bash prompt. I tried echo !!:p but it prints ~/...
1
vote
1answer
2k views

What strings should I look for in /var/log/auth.log?

I wrote a bash command to scan /var/log/auth.log for messages occurring on the current day indicating unauthorised access. Currently it just fetches messages matching BREAK-IN and unauthorized. What ...
42
votes
1answer
13k views

What is $debian_chroot in .bashrc?

What is the debian_chroot variable in my bashrc file? and what is it doing here? PS1='${debian_chroot:+($debian_chroot)}\u@\h:\w\$ '
101
votes
4answers
27k views

Is there a “.bashrc” equivalent file read by all shells?

Is ~/.bashrc the only place to specify user specific environment variables, aliases, modifications to PATH variable, etc? I ask because it seems that ~/.bashrc seems to be bash-only, but other ...
55
votes
6answers
28k views

How to echo a bang!

I tried to create a script by echo'ing the contents into a file, instead of opening it with a editor echo -e "#!/bin/bash \n /usr/bin/command args" > .scripts/command The output: bash: !/bin/...
9
votes
4answers
1k views

Changing the bash prompt

Where is the setting that determines what the bash prompt looks like? Specifically on Arch, but I'm sure others would like to know for other distros too if it's different. Speficially I'd like to use ...
6
votes
1answer
2k views

What does the 'a' attribute in lsattr mean?

I was trying to remove some old history from my .bash_history file, but I was receiving this message: [john ~] /home/john $ mv .bash_history .bas mv: impossible to move `.bash_history' to `.bas': ...
46
votes
3answers
50k views

CLICOLOR and LS_COLORS in bash

I have the following setup in .bashrc for coloring of listings. export CLICOLOR=1 export LS_COLORS='no=00:fi=00:di=00;34:ln=01;36:pi=40;33:so=01;35:do=01;35:bd=40;33;01:cd=40;33;01:or=40;31;01:ex=01;...
3
votes
4answers
4k views

Toggle between dvorak and qwerty

I've recently started to learn the dvorak keyboard layout, but I still need to use qwerty sometimes. I'm looking for a script to toggle between the two keyboard layouts. Also, I'd like to invoke ...
8
votes
2answers
14k views

How to get a program running with root privileges without using su or sudo

I have a bash script that needs to run with root privileges, but must be invoked by the normal user. Difficult part is that the script should not ask for a password, and I don't want to use the ...
9
votes
1answer
3k views

Bash autocomplete in ssh session

It seems that bash doesn't want to autocomplete commands (what's annoying me right now is not autocompleting apt-get) when I'm logged into my machine from SSH. Is there some setting that will allow ...
4
votes
3answers
3k views

Substitute part of text file using bash script

I'm writing a shell script (bash) to fetch and build several bits of software. The script also writes several small config files and needs to alter a couple of pre-existing config files. What is the ...
37
votes
4answers
32k views

How to remove “You have mail” welcome message

When I open up my terminal it says "you have mail", anyone has any idea of why? I am running OS X, but since it too is based on Unix and relies on files such as bashrc, bash_profile etc. I thought ...
6
votes
4answers
7k views

How do I force the user to become root

I have written a bash script for use on my ubuntu box. Now I would like to prevent running this script under my own user and only able to run it as root (sudo). Is there a possibility to force this. ...
0
votes
0answers
157 views

How to mimic zsh named directories with bash [duplicate]

Possible Duplicate: bash directory shortcuts zsh has the concept of named directories, so you can say in ~/.zshrc c=/home/fschmitt/svn/plugin_root : ~c and later use this short cut in the shell ...
5
votes
2answers
2k views

How can I simulate keyboard shortcuts in a bash alias?

For example, one of my bash aliases is this alias p='clear;ls -lt;pwd;' clear also clears the history which I don't want. I just want to clear the screen momentarily. Ctrl+L however does exactly ...
33
votes
6answers
144k views

How do I count the number of occurrences of a word in a text file with the command line?

I have a large JSON file that is on one line, and I want to use the command line to be able to count the number of occurrences of a word in the file. How can I do that?
1
vote
3answers
782 views

build script: how to implement a “skip previously completed step”

I'm trying to create a build script for GCC (which works, for now), but I would like to be able to skip rebuilding all the prereq libraries when I'm only updating GCC/binutils for example. I thought ...
3
votes
1answer
3k views

Array of string expanded to path?

Suppose I have the following initialization of bash array: my_array=( "/usr/bin" "/usr/lib/*.so" ) If I do iteration using: for array_item in ${my_array[@]} do ... done Then the ...
4
votes
3answers
450 views

Randomise or shred memory of an application

Is it possible to randomise or shred memory of a particular application just after its life ends, or better, whenever it deallocates some memory? A command-line utility like this would be perfect: ...
133
votes
2answers
158k views

How to suspend and resume processes

In the bash terminal I can hit Control+Z to suspend any running process... then I can type fg to resume the process. Is it possible to suspend a process if I only have it's PID? And if so, what ...
1
vote
2answers
506 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 \ --host=x86_64-...
0
votes
0answers
340 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 command ...
3
votes
2answers
890 views

Script for ssh Agent Management: Is this adequate? Any bugs?

The following is something I use to manage my ssh agent settings. #!/bin/echo "Must source this:" ## Ensure that ~/.ssh/env contains valid values unset SSH_AGENT_PID SSH_ENV_REFRESH [ -r ~/.ssh/...
6
votes
5answers
9k views

How to find image files by content

I have a list of files and I need to find all the image-files from that list. For example, if my list contained the following: pidgin.tar.gz photo01.jpg picture01 screenshot.gif invoice.pdf Then I ...