7
votes
4answers
9k views
How to make a machine accessible from the LAN using its hostname
Here are details of the machine I want to access using its hostname:
$ hostname
hostname
$ cat /etc/hosts
127.0.0.1 localhost
127.0.1.1 hostname.company.local hostname
It's a default Debian 6 ...
11
votes
3answers
3k views
Removing control chars (including console codes / colours) from script output
I can use the "script" command to record an interactive session at the command line. However, this includes all control characters and colour codes. I can remove control characters (like backspace) ...
3
votes
3answers
4k views
sending text input to a detached screen
I'm trying to run a minecraft server on my unRAID server.
The server will run in the shell, and then sit there waiting for input. To stop it, I need to type 'stop' and press enter, and then it'll ...
17
votes
6answers
2k views
How to understand what's taking up space?
I'm looking for a linux alternative to WinDirStat. I would like to know what is taking up space on my hard drives.
A program that works on console and doesn't require a UI is preferred .
10
votes
3answers
1k views
Does (should) LC_COLLATE affect character ranges?
Collation order through LC_COLLATE defines not only the sort order of individual characters, but also the meaning of character ranges. Or does it? Consider the following snippet:
unset LANGUAGE ...
55
votes
12answers
12k views
How to have tail -f show colored output
I'd like to be able to tail the output of a server log file that has messages like:
INFO
SEVERE
etc, and if it's SEVERE, show the line in red; if it's INFO, in green. What kind of alias can I ...
100
votes
3answers
5k views
What's the difference between $(stuff) and `stuff`?
Running top -p $(pidof init) and top -p `pidof init` gives the same output. Are these two ways of doing the same thing, or are there differences?
43
votes
5answers
849 views
Resources for portable shell programming
What resources exist for portable shell programming? The ultimate answer is to test on all targeted platforms, but that's rarely practical.
The POSIX / Single UNIX specification is a start, but it ...
27
votes
5answers
15k views
What is a Superblock, Inode, Dentry and a File?
From the article Anatomy of Linux File Systems by Tim Jones, I read that Linux views all the file systems from the perspective of a common set of objects and these objects are superblock, inode, ...
45
votes
3answers
10k views
Why do directories need the executable (X) permission to be opened?
In my CMS, I noticed that directories need the executable bit (+x) set for the user to open them. Why is the execute permission required to read a directory?
32
votes
3answers
3k views
What exactly is POSIX?
I see POSIX mentioned often and everywhere, and I had assumed it to be the baseline UNIX standard.. until I noticed the following excerpt on a Wikipedia page: The Open Group
The Open Group is ...
23
votes
10answers
5k views
Get exit status of process that's piped to another
I have two processes foo and bar, connected with a pipe:
$ foo | bar
bar always exits 0; I'm interested in the exit code of foo. Is there any way to get at it?
12
votes
4answers
1k views
Four tasks in parallel… how do I do that?
I have a bunch of PNG images on a directory. I have an application called pngout that I run to compress these images. This application is called by a script I did. The problem is that this script does ...
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?
13
votes
5answers
955 views
Getting information on a machine's hardware in Linux
How can I check what hardware I have? (With BIOS version etc.)
21
votes
4answers
2k views
What's the point in adding a new line to the end of a file?
Some compilers (especially C or C++ ones) give you warnings about:
No new line at end of file
I thought this would be a C-programmers-only problem, but github displays a message in the commit view:
...
15
votes
3answers
1k views
When would you use an additional file descriptor?
I know you can create a file descriptor and redirect output to it. e.g.
exec 3<> /tmp/foo # open fd 3.
echo a >&3 # write to it
exec 3>&- # close fd 3.
But you can do the same ...
10
votes
2answers
1k views
Using an already established SSH channel
I have an already established ssh connection between two machines.
Is there a way to send commands to the remote machine from a shell script that is run on the local machine, using the already open ...
6
votes
1answer
3k views
File descriptors & shell scripting
I am having a very hard time understanding how does one use file descriptors in shell scripts.
I know the basics such as
exec 5 > /tmp/foo
So fd 5 is attached to foo for writing.
exec 6 < ...
11
votes
3answers
4k views
How to find out which (not installed) package a file belongs to?
On Debian systems (and derivatives):
$ dpkg --search /bin/ls
coreutils: /bin/ls
That is, the file /bin/ls belongs to the Debian package named coreutils.
But this only works if the package is ...
18
votes
4answers
2k views
Why do we use “./” to execute a file?
Why do we use ./filename to execute a file in linux?
Why not just enter it like other commands gcc, ls etc...
11
votes
2answers
488 views
gnu find and masking the {} for some shells - which?
The man page for gnu find states:
-exec command ;
[...] The string `{}' is replaced by the current
file name being processed everywhere it occurs in the
arguments to the command, ...
9
votes
6answers
923 views
How can I prepend a tag to the beginning of several files?
I need to add PHP tags surrounding a file. It's easy to append them using
find . -exec echo "?>" >> '{}' \;
but how can I prepend the tag <?php?
4
votes
2answers
3k views
ext4: How to account for the filesystem space?
I've recently formated a 1.5 TB drive with the intention of replacing ntfs with ext4.
Then I noticed that the files I saved don't fit on the new partition.
df:
ext4 (ext3 & ext2 show the same ...
14
votes
5answers
352 views
Keeping track of programs
When I install a simple program it often uses make && make install and doesn't often even have an uninstall target. If I wish to upgrade a program is it standard protocol to assume it just ...
9
votes
5answers
953 views
How to de-unzip, de-tar -xvf — de-unarchive in a messy folder?
Usually, I unarchive things by $ mkdir newFolder; $ mv *.zip newFolder; $ cd newFolder; $unzip *.zip but sometimes I get lazy and just do in an arbitrary folder $ unzip *.zip so time-to-time messing ...
5
votes
2answers
1k views
Creating a UNIX account which only executes one command
Is there a way to create a user account in Solaris which allows the users to run one command only? No login shell or anything else. I could possibly do it with /usr/bin/false in /etc/passwd and just ...
4
votes
5answers
840 views
How to clean up file extensions?
I have a directories with .MP3 files which I'd like to change the extensions to .mp3. What's the easiest way to do this? I'm think something along the lines of:
find /RootPath -type f -iname "*.mp3" ...
76
votes
11answers
33k views
What if 'kill -9' does not work?
I have a process I can't kill with kill -9 <pid>. What's the problem in such a case, especially since I am the owner of that process. I thought nothing could evade that kill option.
38
votes
9answers
21k views
SSH easily copy file to local system
If I'm logged in to a system via SSH, is there a way to copy a file back to my local system without firing up another terminal or screen session and doing scp or something similar or without doing SSH ...
35
votes
10answers
7k views
Recommended reading to better understand Unix/Linux internals
I've worked on *nix environments for the last four years as a application developer (mostly in C).
Please suggest some books/blogs etc. for improving my *nix internals knowledge.
43
votes
6answers
10k views
Keep SSH Sessions running after disconnection
I sometimes have long running processes that I want to kick off before going home, so I create a SSH session to the server to start the process, but then I want to close my laptop and go home and ...
16
votes
3answers
4k views
Restricting an SSH/SCP/SFTP user to a directory
Is there a simple way to restrict an SCP/SFTP user to a directory? All methods that I've come across require me to set a chroot jail up by copying binaries, but I don't think that should be necessary.
...
13
votes
7answers
7k views
Lightweight outgoing SMTP server
What do you use as a lightweight SMTP for outgoing e-mails only?
I am running an app that sends e-mails via SMTP when events occur once in a while, and I don't need a fully featured e-mail server.
...
17
votes
8answers
7k views
Different ways to execute a shell script
There a several ways to execute a script, the ones I know are:
/path/to/script # using the path (absolute or relative)
. script # using the . (dot)
source script # using the `source` command
...
18
votes
3answers
2k views
using single or double bracket - bash
I'm confused with using single or double bracket. look at code:
dir="/home/mazimi/VirtualBox VMs"
if [[ -d ${dir} ]]; then
echo "yep"
fi
It works perfectly although the string contains space. ...
15
votes
3answers
2k views
How can I use two bash commands in -exec of find command?
Is it possible to use 2 commands in the -exec part of find command ?
I've tried something like:
find . -name "*" -exec chgrp -v new_group {} ; chmod -v 770 {} \;
and I get:
find: missing ...
13
votes
2answers
2k views
Understanding IFS
The following few threads on this site and StackOverflow were helpful for understanding how IFS works:
What is IFS in context of for looping?
How to loop over the lines of a file
Bash, read line by ...
3
votes
6answers
898 views
Common multiple SSH connections file handling issue
often I have to download a file that isn't directly accessable via the first SSH connection. For example I'm on a Windows machine and I want to access another machine that is only accessable from lan. ...
6
votes
2answers
838 views
Find filesystem of an unmounted partition from a script
I'm writing a custom automated install using AIF (Arch Installation Framework), and I need to find the filesystem on a partition given a partition.
So far I have this:
grok_partitions () {
local ...
8
votes
1answer
540 views
Run a command for a specified time and then abort if time exceeds
I want know how I can run a command for a specified time say, one minute and if it doesn't complete execution then I should be able to stop it.
3
votes
4answers
4k views
Renaming multiple files (changing extension)
I would like to change file extension from *.txt file to *.text file, tried using the basename command, but I am having trouble on changing more than 1 file, I am getting a basename: too many ...
14
votes
1answer
1k views
Is there a way in bash to redirect output and still have it go to stdout?
Okay. If I wanted to redirect the output of a program to a file, I'd do something like this
prog > file
If I wanted to redirect both stdout and stderr to that file, then I'd do
prog > file ...
10
votes
1answer
377 views
How do ${0##*/} and ${0%/*} work?
I'm quite confused about the following regular expressions I found in a shell script:
${0##*/}
${0%/*}
How do they work?
3
votes
3answers
7k views
Shell Script for logging into a ssh server
I tried writing a shell script which can do automatic login into a ssh server using password which is mentioned in the script. I have written the following code:
set timeout 30
/usr/bin/ssh -p 8484 ...
2
votes
2answers
683 views
Installation on debian 5 32-bit without being a root
I am new to Linux and I am trying to install Skype and Google Chrome on my desktop. It runs Debian 5 32-bit. I downloaded the packages from the web but I have no idea how to install them. I have ...
5
votes
1answer
263 views
LoggedFS configuration file syntax
What is the syntax of the LoggedFS configuration file?
The official documentation only had usage instructions for the loggedfs command and a configuration file example. Ok, it's XML, but what are ...
1
vote
1answer
1k views
“No such file or directory” lies on Optware installed binaries
I've been using Optware to install packages on my ARM-based NAS for a while - the usual stuff like Transmission, Samba and others. However, I'd been having problems with Transmission hanging not long ...
75
votes
13answers
10k views
How to do integer & float calculations, in bash or other languages?
Using echo "20+5" literally produces 20+5
What command can I use to get the actual sum, e.g. 25 in this case.
Also, what's the easiest way to do it just using bash for floating point, e.g.
echo ...
69
votes
7answers
7k views
Which is the safest way to get root privileges: sudo, su or login?
I would like to have the root account in safety even if my unprivileged user is compromised.
On Ubuntu you can only use sudo for "security reasons" by default. However I am not sure it is any safer ...
