Bash is the Bourne Again SHell, the successor to the classic Unix sh (shell).

learn more… | top users | synonyms (1)

0
votes
3answers
6k views

crontab to run bash script (ssh command in it) not working

CentOS 5.4 (in my script file - script.sh) #!/bin/bash ssh 192.168.0.1 'iptables -L' > /tmp; (in /etc/crontab) 30 21 30 9 * root /bin/bash /script.sh If I run the script in terminal, things ...
-3
votes
2answers
66 views

How to compare today's date against an array of dates [closed]

I want to create an array of dates and compare it to today's date if it matches then execute test.sh file otherwise exit the loop in bash script. I have this so far: #!/bin/bash now=$(date +%Y-%m-%d) ...
121
votes
27answers
46k views

How do I prevent accidental rm -rf /*?

I just ran rm -rf /* accidentally, but I meant rm -rf ./* (notice the star after the slash). alias rm='rm -i' and --preserve-root by default didn't save me, so are there any automatic safeguards for ...
56
votes
12answers
32k views

How can I run arbitrarily complex command using sudo over ssh?

I have a system that I can only log in to under my username (myuser), but I need to run commands as other user (scriptuser). So far, I have come up with the following to run the commands I need: ssh -...
64
votes
13answers
93k views

What's the best way to check if a volume is mounted in a Bash script?

What's the best way to check if a volume is mounted in a Bash script? What I'd really like is a method that I can use like this: if <something is mounted at /mnt/foo> then <Do some ...
55
votes
3answers
20k views

What are the functional differences between .profile .bash_profile and .bashrc

What are the functional differences between the .profile, .bash_profile and .bashrc files?
33
votes
7answers
101k views

How can I edit the welcome message when ssh start?

I have a vps for my website hosting. It is running a ubuntu server. Every time I logged in my server by ssh, it displays a lengthy welcome message in my terminal. Linux node61.buyvm.net 2.6.18-...
31
votes
6answers
22k views

Merge 2 directory trees in Linux without copying?

I have two directory trees with similar layouts, i.e. . |-- dir1 | |-- a | | |-- file1.txt | | `-- file2.txt | |-- b | | `-- file3.txt | `-- c | `-- file4.txt `-- ...
52
votes
8answers
51k views

How to make bash scripts print out every command before it executes?

For example, I have a simple bash file #!/bin/bash cd ~/hello ls How can I make it display every command before executing it? Just the opposite effect of "@echo off" in windows batch scripting.
40
votes
1answer
11k views

What is the difference between a 'Login' and an 'Interactive' bash shell

What is the difference between a ‘Login’ and an ‘Interactive’ bash shell? I have quoted Wikipedia below but can anybody give a better answer? EDIT: This is a community wiki so maybe rather than ...
33
votes
4answers
40k views

run script as user who has nologin shell

All I need to do is to run a specific script as a particual user who does have the nologin/false shell indicated in /etc/passwd. I would run the script as root and this should run as another user. ...
21
votes
8answers
16k views

How do I ask screen to behave like a standard bash shell?

Just learned about the screen command on linux - it is genius. I love it. However, the actual terminal/prompt in screen looks and behaves differently than my standard bash prompt. That is, the ...
28
votes
4answers
12k views

Run an interactive bash subshell with initial commands without returning to the (“super”) shell immediately

I want to run a bash subshell, (1) run a few commands, (2) and then remain in that subshell to do as I please. I can do each of these individually: Run command using -c flag: $> bash -c "ls; pwd;...
8
votes
14answers
6k views

What are some informative and useful shell prompts? (Bash, csh, ksh, etc.)

One of my favorite Mac OS X Terminal tips involves adding the last running process into the terminal title using the following code in your .bashrc. trap 'printf "\033]0; `history 1 | cut -...
7
votes
6answers
8k views

crontab environment

I have written various scripts to launch Java server applications, which are typically run for 24 hours before being shut down (by invoking the same script with a different parameter). The script ...
28
votes
2answers
22k views

How to apply a filter to real time output of `tail -f `?

tail -f path The above will output modifications to the file instantly, but I want to apply a filter to the output, only show when there is a keyword xxx in it. How to approach this?
14
votes
1answer
934 views

Can Bash Tell Me Which SSH Public Key Was Used To Authenticate?

Let's say I want to track my root users. Each of them has a unique private key and their public keys have been stored in /root/.ssh/authorized_keys. Given that each user logs in with their unique key ...
8
votes
6answers
27k views

How should someone create an encrypted password for /etc/shadow?

I am setting up a new account on a Linux box for Subversion repository access, and can send the password to the new user. However, I think there was a command line utility for this new user to encrypt ...
38
votes
6answers
43k views

What is “-bash: !”: event not found"

Try executing the following under a bash shell echo "Reboot your instance!" On my installation: root@domU-12-31-39-04-11-83:/usr/local/bin# bash --version GNU bash, version 4.1.5(1)-release (i686-pc-...
22
votes
14answers
42k views

Stop ssh login from printing motd from the client?

I've got SSH passwordless set up, however it prints the MoTD when it logs in. Is there anyway to stop that happening from the client side? I've tried ssh -q but that doesn't work. I don't want to use ...
7
votes
1answer
1k views

Will this HAProxy “restart script” work as gracefully I think it will?

I put this script together from various places. What I am hoping is that it will do the following once run: Pause all "NEW" http traffic for ports 80 and 443 - just "pause" them, don't give any ...
5
votes
5answers
838 views

Interactive shell tips?

What are some of your favorite shell tips? Stuff that makes your every day command line use that much easier? Mine, for bash: Add this to the .inputrc file in your home dir: "\e[A": history-search-...
10
votes
2answers
5k views

Fix for bash line-wrapping & backspace display bugs on Mac OS X?

When I open up Terminal (on Mac OS X 10.5.8) and type a long command line: ...the text doesn't go to the next line when it wraps around: Also, sometimes when I type a command and then backspace (...
9
votes
3answers
15k views

Linux gzip multiple subdirectories into separate archives?

How would I be able to compress subdirectories into separate archives? Example: directory subdir1 subdir2 Should create subdir1(.tar).gz and subdir2(.tar).gz
17
votes
5answers
22k views

Force SSH to use a specific shell

Is there any way to force SSH to use a particular shell on the remote end, regardless of what the user's default shell is? I've tried solutions akin to: ssh host.domain.com /bin/bash -c 'complicated,...
15
votes
3answers
2k views

Strange bash history behaviour when running multiple sessions

How is command line history stored when I use multiple terminal windows? I know it is stored in .bash_history but I can't see the logic on what history is used if I open new window. It almost feels ...
10
votes
3answers
13k views

iftop - how to generate text file with its output?

iftop is great tool to view almost live bandwidth usage distinguished by source-ip source-port destination-ip destination port. I'm using it to see which client's ip is using most bandwidth. Now I ...
10
votes
1answer
3k views

Where is $BASH_ENV usually set?

I have twin Linux servers that should be configured identically, however ssh commands to one of them are failing for commands that require a path that's specified in ~/.bashrc. For example, I can use ...
7
votes
3answers
3k views

Copy a file's owner permissions to group permissions

How can I copy a file's user/owner permissions to it's group permissions? For example if the permissions are 755 I want them to become 775. Clarification: 755 -> 775 123 -> 113 abc -> aac Bonus if ...
4
votes
5answers
5k views

Multithreaded downloading with shell script

Let's say I have a file with lots of URLs and I want to download them in parallel using arbitrary number of processes. How can I do it with bash?
17
votes
2answers
15k views

How do ulimit -n and /proc/sys/fs/file-max differ?

I notice that on a new CentOS image that I just booted up off of EC2 that the ulimit default is 1024 open files, but /proc/sys/fs/file-max is set at 761,408 and I'm wondering how these two limits work ...
11
votes
2answers
3k views

How does the updated Shellshock vulnerability test for CVE-2014-7169 work?

I understand the original test for CVE-2014-6271, which was: $ env x='() { :;}; echo vulnerable' bash -c "echo this is a test" But I'm confused by the updated test and corresponding output for CVE-...
8
votes
7answers
6k views

In *nix, how to determine which filesystem a particular file is on?

In a generic, modern unix environment (say, GNU/Linux, GNU/Solaris, or Mac OS X), is there a good way to determine which mountpoint and filesystem-type a particular absolute file path is on? I ...
6
votes
4answers
6k views

Starting a script as another user

I've created a script in /etc/init.d/ which has to run several other scripts from other (non-root privileged) users from their home directories, as if they started them. I launch these scripts with:...
5
votes
2answers
3k views

Is there a way to configure bash to always page output?

I'd like to configure bash to page the output of all commands. Essentially, I want bash to behave as if every command I enter ended with '| less'. Is this possible?
5
votes
2answers
1k views

What is the purpose of each of the different UNIX/Linux shell startup files?

Previously, when setting up a *NIX environment for the first time, I would put all of my shell customisations into .bashrc, with the following .bash_profile: if [ -f $HOME/.bashrc ]; then . $HOME/...
5
votes
4answers
3k views

GNU screen loses (parts of) command histories

I use GNU screen with 5 different sessions, each of which stores its own command history. But often I don't find a command in the history, although I'm sure I've used it exactly in the session I'm ...
4
votes
3answers
5k views

How can I easily convert HTML special entities from a standard input stream in Linux?

CentOS Is there an easy way to convert HTML special entities from a data stream? I'm passing data to a bash script and sometimes that data includes special entities. For example: "test" ...
2
votes
3answers
1k views

Bash completion dynamic behavior

I would like to have 2 different behavior of "tab" depending of the usage context. I would like to have the default behavior of bind '"\t":complete' any time except when users are trying to complete ...
16
votes
4answers
22k views

How do I patch RHEL 4 for the bash vulnerabilities in CVE-2014-6271 and CVE-2014-7169?

A mechanism for remote code execution through Bash has been widely reported yesterday and today (September 24, 2014.) http://seclists.org/oss-sec/2014/q3/650 Reported as CVE-2014-7169 or CVE-2014-6271 ...
9
votes
4answers
12k views

Can not update Bash on Debian 6.0 (Squeeze)

I can not update Bash on a Debian 6.0 (Squeeze) server to get rid of the discovered vulnerability: bash --version GNU bash, version 4.1.5(1)-release (x86_64-pc-linux-gnu) apt-get update apt-get ...
6
votes
2answers
1k views

Bash: menu-complete only for few matches

With Bash auto-completion, is there a way to cycle through matches using menu-complete only if there are 1-2 options, and use listing with complete otherwise? Example home directory contains Desktop,...
5
votes
1answer
737 views

how to pre-create directories on linux for file storage

looking for a way to pre-create directories on linux to be used to store a large number of files. We will be generating file ids using a GUID - I need to keep a copy of these files on a linux web ...
4
votes
5answers
3k views

Bash: Quotes getting stripped when a command is passed as argument to a function

I am trying to implement a dry run kind of mechanism for my script and facing the issue of quotes getting stripped off when a command is passed as an argument to a function and resulting in unexpected ...
2
votes
2answers
820 views

How to get dig +short to return something when there is no answer?

The behavior of dig +short is to return nothing (null) when running a query that returns no answer (nothing to do with timeout, just an empty answer). This is ok when running a query by itself, but ...
1
vote
3answers
1k views

Run FTP session from bash script

I'm trying to write a BASH script to test if an FTP site that I own is running. I therefore want the bash script to connect to the FTP site, log in with a dummy account and redirect the output to a ...
1
vote
3answers
7k views

Appending a line to a file if it doesn't exist using Puppet

I've got a defined resource type to append a line to a file if it doesn't exist, as per below: define appendLineToFile($file, $line, $user) { exec { "echo \"\\n$line\" >> \"$file\"": ...
0
votes
1answer
983 views

Disable the ability to hide bash command history

User can hide the command history in bash by either append a space before the command unset HISTFILE How to disable this?
6
votes
6answers
12k views

What is a recommended way to patch the Shellshock Bash bug on an unsupported Ubuntu server?

I maintain an out-of-support Ubuntu 12.10 (Quantal Quetzal) server (don't ask me why, please), and we need to patch the Shellshock Bash security bug. As upgrades are not available anymore, what ...
6
votes
1answer
813 views

Providing normal users(non-root) with initialization and shutdown auto-run capabilities

I'm hosting an experimental/testing Linux box, running Debian Wheezy 7.4.0 distribution. Different users log into the machine over ssh to their accounts and are allowed to run the development tools ...