Questions tagged [scripting]

A form of computer programming that — in the context of system administration — lends it self well to automating tasks.

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778
votes
13answers
1.1m views

How to determine if a bash variable is empty?

What is the best way to determine if a variable in bash is empty ("")? I have heard that it is recommended that I do if [ "x$variable" = "x" ] Is that the correct way? (there must be something more ...
441
votes
5answers
196k views

What is the difference between double and single square brackets in bash?

I just wondered what exactly the difference between [[ $STRING != foo ]] and [ $STRING != foo ] is, apart from that the latter is posix-compliant, found in sh and the former is an extension found ...
144
votes
11answers
280k views

Run a .bat file in a scheduled task without a window

I have a scheduled task that starts a batch script that runs robocopy every hour. Every time it runs a window pops up on the desktop with robocopy's output, which I don't really want to see. I ...
120
votes
7answers
150k 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-...
89
votes
8answers
104k 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.
81
votes
7answers
33k views

Why use Chef/Puppet over shell scripts?

New to Puppet and Chef tools. Seems like the job that they are doing can be done with shell scripting. Maybe it was done in shell scripts until these came along. I would agree they are more readable. ...
80
votes
12answers
62k 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
6answers
32k views

What does passing the -xe parameters to /bin/bash do

Exactly what the title says. I'm not having much luck finding the proper documentation to see what -xe does in the following use case: #!/bin/bash -xe what do those parameters do and where it is ...
51
votes
9answers
71k views

How do I run a local bash script on remote machines via ssh?

I am looking for a way to push configuration from one central machine to several remote machines without the need to install anything on the remote machines. The aim is to do something like you ...
49
votes
6answers
168k views

How can I fully log all bash scripts actions?

From my script output I want to capture ALL the logs data with error messages and redirect them all to log file. I have script like below: #!/bin/bash ( echo " `date` : part 1 - start " ssh -f ...
48
votes
9answers
116k views

Tool to test a user account and password (test login)

Yeah, I can fire up a VM or remote into something and try the password...I know...but is there a tool or script that will simulate a login just enough to confirm or deny that the password is correct? ...
42
votes
8answers
171k views

Run a shell script as a different user

What's a good way of running a shell script as a different user. I'm using Debian etch, and I know which user I want to impersonate. If I was doing it manually, I would do: su postgres ./backup_db....
42
votes
10answers
149k views

How do I check the build status of a Jenkins build from the command line?

How do I check the Jenkins build status without switching to the browser? If required, I can create a script using the JSON API, but I was wondering if there is already something like this built in.
39
votes
5answers
231k views

Need to add a “Wait” command to a Powershell script

Here is my current code: Write-output “ENTER THE FOLLOWING DETAILS - When Creating Multiple New Accounts Go to EMC hit F5(refresh) and make sure previous new account is listed before ...
35
votes
4answers
62k views

What is needed for a linux service to be supported by chkconfig?

I am trying to add to the auto start at boottime a linux service through the chkconfig -add <servicename> and I get a message saying service <servicename> does not support chkconfig ...
33
votes
8answers
18k views

Is there any reason to use bash over zsh? [closed]

I'm curious about why one would want to run bash instead of zsh. I mean zsh is fully backwards-compatible with bash. Don't get me wrong: I don't dislike bash or anything. I just genuinely want to ...
33
votes
5answers
42k views

Where is a good permanent place to install custom bash scripts?

I'm about to install "leiningen" which is a bash script for the clojure programming language with a lot of usefulness... ...but I'm not sure where it is appropriate to -put- a executable script in ...
30
votes
6answers
44k views

What command prints a string as “big ascii text art” in bash? [closed]

I'm looking for a program that turns an ASCII string into something like the "ascii art" below: .-"^`\ /`^"-. .' ___\ ...
30
votes
8answers
83k views

Multi-select menu in bash script

I'm a bash newbie but I would like to create a script in which I'd like to allow the user to select multiple options from a list of options. Essentially what I would like is something similar to the ...
30
votes
5answers
4k views

How can a Linux Administrator improve their shell scripting and automation skills?

In my organization, I work with a group of NOC staff, budding junior engineers and a handful of senior engineers; all with a focus on Linux. One interesting step in the way the company grows talent is ...
29
votes
14answers
19k views

How do I find out what version of Linux is running?

Sometimes your scripts need to behave differently on different Linux's. How can I determine which version of Linux a script is running on?
28
votes
3answers
23k views

Passing default answers to apt-get package install questions?

I'm trying to write a configuration script for new servers, and one of the first steps is to install a series of required packages, such as MySQL, phpMyAdmin, etc. using apt-get install However, when ...
27
votes
3answers
45k views

Can I use rsync to create a list of only changed files?

I am using rsync in a bash script to keep files in sync between a few servers and a NAS. One issue I have run into is trying to generate a list of the files that have changed from the during the rsync....
26
votes
13answers
76k views

Need leading zero for batch script using %time% variable

I came across a bug in my DOS script that uses date and time data for file naming. The problem was I ended up with a gap because the time variable didn't automatically provide leading zero for hour &...
26
votes
7answers
24k views

Bash Scripting: Require script to be run as root (or with sudo)

I'm trying to write a bash script (in Ubuntu) that will backup a directory using tar. How can I do a check in the script so that it can only be run as root (or with sudo)? For instance, if a user ...
26
votes
13answers
1k views

How to encourage Windows administrators to pick up scripting? [closed]

When I worked as an administrator in my first job, I was frustrated that our administration processes with Windows servers were a series of point-and-clicks; we could never match the level of ...
25
votes
3answers
251k views

For Loop counting from 1 to n in a windows bat script

I need to run a windows command n times within a bat script file. I know how to do this in various programming languages but cannot manage to get it right on the windows command line :-( I would ...
24
votes
9answers
61k views

How do I read multiple lines from STDIN into a variable?

I've been googling this question to no avail. I'm automating a build process here at work, and all I'm trying to do is get version numbers and a tiny description of the build which may be multi-line. ...
24
votes
4answers
41k views

How to configure postfix to pipe all incoming email to a script?

Using postfix, I'd like all incoming mail, to any address (including those that don't map to local users) to be piped to a script. I've tried configuring mailbox_command in /etc/postfix/main.cf: ...
23
votes
5answers
18k views

Scripted install of MySQL on Ubuntu

I need to write a script that will build my server from a fresh Ubuntu server install. Among things like Apache and PHP it needs to install MySQL. The only problem here is that when I install MySQL ...
22
votes
5answers
4k views

Temporarily increasing sudo's timeout for the duration of an install script

I'm trying to write a script that will install a bunch of software and I'd like to not have to run everything as root, so I'd like to be able to prompt for a password and then go about the install, ...
21
votes
5answers
45k views

How to Automatically and Temporarily block an IP address making too many hits on the Server in a short timespan?

One of my LAMP servers was recently brought down by some kind of script bot looking for exploits. From the looks of it, it was making so many requests a second, that it overloaded the RAM on the ...
21
votes
7answers
16k views

Setting the Timezone with an automated script

I'm writing scripts to automate setting up new slicehost installations. In a perfect world, after I started the script, it would just run, with no attention from me. I have succeeded, with one ...
20
votes
7answers
7k views

Sort a list of domain names (FQDNs) starting from tld and working left

I am looking to sort a list of domain names (a web filter whitelist) starting from the TLD and working upwards. I am looking any *nix or windows tools that can do this easily, though a script would ...
19
votes
4answers
42k views

How to run script via SSH that doesn't end when I close connection?

I need to run script, that takes long time to execute, or I just want it to run forever. I can't just SSH to my machine, because when I disconnect it stops running. Is there any way to run script ...
19
votes
14answers
4k views

What are some good resources for learning PowerShell scripting? [closed]

Are there online resources or books that you would recommend as an introduction to PowerShell scripting? The resources I've found primarily focus on interactive use.
19
votes
8answers
2k views

How do I become a scripting guy? [closed]

I am a fairly new Windows Systems Administrator. I have done some basic batch files and some other scripting. I would like to know what path I should take to become a better scripter. What language ...
19
votes
1answer
4k views

Shell command slow when using pipe, fast with intermediate file

Does anyone understand this huge difference in processing time, when using an intermediate file, or when using a pipe? I'm converting tiff to pdf using standard tools on a fresh debian squeeze server. ...
18
votes
9answers
93k views

script to automatically test if a web site is available

I'm a lone web developer with my own Centos VPS hosting a few small web sites for my clients. Today I discovered my httpd service had stopped (for no apparent reason - but that's another thread). I ...
18
votes
3answers
50k views

scp files and delete files on remote directory [closed]

I am a unix noob, so please be patient :-) I have a script that scps a bunch of files to another server. Suppose they are z1.foo, z2.foo etc. What I want to do is to scp files and delete files older ...
17
votes
4answers
6k views

In CentOS 4.4, how can I strip escape sequences from a text file?

What command can I use to strip color-code escape sequences from a text file? Ideally something I can pipe through. If I have a file with a bunch of coloured text rainbow.txt, what goes in the gap: ...
17
votes
5answers
23k views

How to automatically run a script when the contents of a directory changes in Linux?

I want to automatically run a script whenever new files are copied into a particular directory. In other words, is there a way in Linux to "watch" a directory for changes and then run something in ...
17
votes
13answers
15k views

Scripting alternatives to Bash shell scripts

I have just migrated to a UNIX workstation. My memory of Bash shell scripts has faded since school and I find the syntax to be highly confusing. I am wondering what other scripting languages are ...
16
votes
4answers
90k views

Find GUID of MSI Package

How can I find the GUID of an MSI package? I would like to script the removal of a program on a large number of desktops by using: msiexec.exe /x ProductCode Any reason why this would not work ...
16
votes
5answers
63k views

What version of Windows Management Framework is installed?

How do you check to see what version of Windows Management Framework (WMF) is installed? It seems like it should be a simple thing to find out, but I cannot. Even Googling a bunch of different ...
16
votes
3answers
129k views

Using ICACLS to set permissions on user directories

I'm trying to reset permissions on user directories and having a bit of trouble with the last step of my script. My script basically takes ownership of the entire user directory, resets the ...
14
votes
4answers
53k views

How to use a config file (ini, conf,…) with a PowerShell Script?

Is it possible to use a configuration file with a PowerShell script? For example, the configuration file: #links link1=http://www.google.com link2=http://www.apple.com link3=http://www.microsoft.com ...
14
votes
6answers
18k views

Using mysqldump in cron job without root password

If I login with the root password on my box I can simply type mysqldump --all-databases and I will get th expected "Dump". I setup a job in cron.daily to run and dump this to a backup drive. The ...
14
votes
4answers
13k views

Best book for learning linux shell scripting? [closed]

I normally works on Windows machines but on some occasions I do switch to development on linux. And my most recent project will be written entirely on a certain linix platforms (not the standard ...
13
votes
4answers
8k views

Vim - Trigger action\script on save\write?

This might be better for super user, but I figure as a tool of the trade it might be a better topic for here. I find often when editing in vim that I exit out, run some script that I am testing, and ...