A script is a sequence of commands or instructions that are executed by an interpreter program rather than compiled into a standalone executable program.
31
votes
5answers
17k views
Allow setuid on shell scripts
The setuid permission bit tells Linux to run a program with the effective user id of the owner instead of the executor:
> cat setuid-test.c
#include <stdio.h>
#include <unistd.h>
int ...
21
votes
5answers
3k views
What Unix commands can be used as a semaphore/lock?
I want to run multiple Bash shell scripts in parallel. However, I want to avoid race conditions. What Unix commands are truly atomic that I could use for this purpose, and how can I use them?
16
votes
7answers
20k views
Looping through files with spaces in the names?
I wrote the following script to diff the outputs of two directores with all the same files in them as such:
#!/bin/bash
for file in `find . -name "*.csv"`
do
echo "file = $file";
diff ...
5
votes
3answers
1k views
What is IFS in context of for looping?
I'm learning bash scripting right now.
I was reading this thread: How to loop over the lines of a file?
What is IFS?
With for and IFS:
5
votes
3answers
2k views
Storing output of command in shell variable
I have an operation using cut that I would like to assign result to a variable
var4=ztemp.xml |cut -f1 -d '.'
I get the error:
ztemp.xml is not a command
The value of var4 never gets ...
85
votes
16answers
38k views
Repeat a Unix command every x seconds forever
There's a builtin Unix command repeat whose first argument is the number of times to repeat a command, where the command (with any arguments) is specified by the remaining arguments to repeat. For ...
21
votes
2answers
2k views
What does “3>&1 1>&2 2>&3” do in a script?
I saw this line in a script:
DEVICE=`dialog --inputbox "Festplatten-Laufzeit auslesen. Gebe Sie das
gewünschte Device an: " 0 70 "" 3>&1 1>&2 2>&3`
What is
3>&1 ...
13
votes
8answers
3k views
Object-oriented shell for *nix
Preface: I love bash and have no intention of starting any sort of argument or holy-war, and hopefully this is not an extremely naive question.
This question is somewhat related to this post on ...
5
votes
4answers
570 views
Automatically run commands over SSH on many servers
There is a list of IP addresses in a .txt file, ex.:
1.1.1.1
2.2.2.2
3.3.3.3
Behind every IP address there is a server, and on every server there is an sshd running on port 22. Not every server is ...
7
votes
3answers
454 views
How to pipe the list of commands displayed by of “tab complete”?
When using commands in bash I like the double tab option to display the available commands. Some commands have more possible matches than others:
Is there a way I can pipe the output of the double ...
3
votes
2answers
533 views
How to do a text replacement in a big folder hierarchy?
I want to search and replace some text in a large set of files excluding some instances. For each line, I want a prompt asking me if I need to replace that line or not.
Something similar to vim's ...
6
votes
5answers
467 views
How can I have more than one possibility in a script's shebang line?
I'm in a bit of an interesting situation where I have a Python script that can theoretically be run by a variety of users with a variety of environments (and PATHs) and on a variety of Linux systems. ...
5
votes
2answers
1k views
Privoxy: blocking twitter, facebook and google outside of their domainslr
Related subject: blocking facebook.com outside facebook.com domain
This is from default.filter
#################################################################################
#
# shockwave-flash: ...
5
votes
5answers
351 views
Shell programming, avoiding tempfiles
I often write KSH shell scripts that follow the same pattern:
(1) retrieve output from one or more command
(2) format it using grep|cut|awk|sed and print it to the screen or to a file
In order to ...
6
votes
3answers
1k views
How to “send” variable to sub-shell?
I run the following script:
VAR="Test"
sh -c 'echo "Hello $VAR"'
But I get :
# ./test.sh
Hello
How can I "send" the variable VAR of my script to the shell created with sh -c?
3
votes
2answers
2k views
How to copy someone's else folders from public.me.com with a wget-like tool?
How can I copy a folder from http://public.me.com/ (a service related to iDisk, or MobileMe) to my local filesystem with a Unix tool (like wget, a command-line non-interactive tool)?
The problem is ...
1
vote
2answers
239 views
stdout , stderr and logging using the script command
I have remove.sh which contains:
rm -v test.tmp
And I have install.sh which contains:
script remove.log -c './remove.sh'
What can I do so that whether or not test.tmp exists, I don't see any rm ...
0
votes
1answer
381 views
/bin/sh: ./check-dependencies.pl: not found — but check-dependencies.pl exists!
I'm trying to build Moses, but when I run make I get the following output:
minakshi@minakshi-Vostro-3500:~/Desktop/working-dir/moses/scripts$ make release
# Compile the parts
make all
make[1]: ...
0
votes
2answers
172 views
Autentification on SSH connection in OneLine [duplicate]
Possible Duplicate:
Shell Script for logging into a ssh server
I need to connect via SSH to a remote server, however I must do this with out interactive mode and with out use Public keys ...
13
votes
7answers
4k views
Faster way than ping for checking if computer online?
I'm writing a wake on lan script for a set of our lab computers. We have sqlite db with a list of the computer hostnames, IPs, and MACs and currently I ping each of them with '-c1' so it doesn't run ...
4
votes
1answer
365 views
Shell script printing the most visited directories
Is there a way to write a bash script with the following functionalities?
Be launched when I press some key or key combination. (not so important requirement)
Identify the 7 most visited directories ...
2
votes
4answers
2k views
Backup of LVM2 logical volume
I'd like to make backup on external drive of LVM2 logical volume in dd manner.
Approach I consider is to
make lv on extranl drive with identical size
copy with dd
(Please let me know if you see ...
11
votes
3answers
933 views
What does it mean to have a $“dollarsign-prefixed string” in a script?
I just saw this in an init script:
echo $"Stopping Apache"
What is that dollar-sign for?
My research so far:
I found this in the bash manual:
extquote
If set, $'string' and ...
9
votes
4answers
2k views
Script to change current directory (cd, pwd)
I want to run a script to simply change the current working directory:
#!/bin/bash
cd web/www/project
But, after I run it, the current pwd remains unchanged! How can I do that?
7
votes
1answer
599 views
confirmed exit using trap
I am trying to trap the Ctrl+C signal asking a confirmation from the user. The trapping part works fine. But once the signal gets trapped, it does not return to the normal execution. Instead, it quits ...
6
votes
2answers
918 views
List elements with spaces in zsh
I've been studying zsh scripting for all of 2 hours at this point and I've hit a wall. I want to go through a list of files that may have spaces in them. I'm open to completely different approaches ...
7
votes
6answers
3k views
Extracting nested zip files
I have numerous zip archives, each of which contains a number of zip archives. What is the best way to recursively extract all files contained within this zip archive and its child zip archives, that ...
3
votes
2answers
345 views
Convert a typescript file to a list of commands (history)
I wanted to record a linux session so I could use it as documentation for a "how to install" guide. I found something on the internet that suggested that the script command would be good for this, and ...
1
vote
3answers
1k views
Need a loop to sleep for a fraction of second
On my machine I need to execute a cycle that iterates 1 simple command that must have a delay expressed in fractions of second.
Let's say that I need:
to save a file with an increasing enumaration ...
1
vote
2answers
390 views
How can I queue processes?
I have a surveillance camera and a program records videos when motion is detected. Basically, this program saves the video in a very heavy format.
My solution was to call a script that converts the ...
6
votes
2answers
457 views
sync files recursively between two folders where files are less than 24 hours old
I want to find all the files under a directory which are within 24 hours then rsync those files with another server.
There are some old files that I do not want to transfer, however if those old ...
4
votes
3answers
2k views
Can IFS (Internal Field Separator) function as a single seperator for multiple consecutive delim chars?
Parsing an array using IFS with non-whites space values creates empty elements.
Even using tr -s to shrink multiple delims to a single delim isn't enough.
An example may explain the issue more ...
3
votes
2answers
135 views
Exiting a pipeline if a former command fails
I'm trying to check the number of running and queued PBS jobs by parsing the output of qstat -tn1 from a bash script.
So far, this has worked:
count ()
{
qstat -tn1 | awk '
BEGIN { R = 0; ...
2
votes
3answers
61 views
Scripting to domain allocation to server
I have two text files:
file #1: domain.txt
cocacola.com
airtel.com
pepsi.com
file #2: servers.txt
192.0.53.42 , 4 # 4 domains already allocated on server 192.0.53.42
192.53.1.2 , 1 # 1 ...
2
votes
3answers
136 views
What is the difference between ./script and . ./script? [duplicate]
Possible Duplicate:
Using ‘.’ to execute files in bash
I was trying to figure out how to export my environmental via script instead of changing my .bashrc file.
I found this old useful ...
2
votes
1answer
252 views
Script for courier maildir folders on CentOS LAMP environment
I'm looking for resources to help me build a script to do monthly maintenance of maildir folders for a typical CentOS LAMP VPS hosting environment.
I would like to run a script that runs from a ...
0
votes
1answer
329 views
Script with root permission [duplicate]
Possible Duplicate:
Redirecting stdout to a file you don't have write permission on
I am creating a script to change the brightness of my laptop. I discovered that I can do this using
...
