Linux Shell Basics

Stéphane Lenclud · Apr 2, 2017

Batch chmod
Find command
Downloading
Debian Aptitude
Symbolic link
Create an empty file
To do deltree
Console text editor
Handle TGZ file
Memory information
Run all daily cron jobs
Free disk space
Debian shell prompt
Send file through FTP
Process status
Kernel module
Date display
References

On that page you find some tips on how to do things from the command line on Linux.

Batch chmod

I'm no Linux crack, so I won't be able to tell you how many variants there are of Shell languages out there. In fact I don't even know what version of Shell I've been using myself.

I had to change some file permissions the other day when deploying some web site. To do that I used the following shell script:

Bash:

#!/bin/bash
folders=`find -xtype d`
for folder in $folders ; do
chmod -v 775 "$folder"
done

It gets the list of sub-directories put it in a variable and then executes a chmod for each of them. Later on I find out that I could have done the same thing in one single line:

Bash:

find . -type d -exec chmod 775 {} \;

I haven't tried that yet though.

Find command

Find files in the current directory that do not contain '.' character besides the first character:

Bash:

find . -maxdepth 1 -type f -regex '\.[^\.]*'

Find all the file from the current directory with .conf extension and containing the string "LoadModule".
Grep flag -H prints the name of the file and -i flag makes the search case insensitive search:

Bash:

find . -type f -regex .*\.conf -exec grep -H -i LoadModule {} \;

Find all files with a name matching LeftBar but not matching WebLeftBar:

Bash:

find . -name "[b]LeftBar[/b]" ! -name "WebLeftBar*"

Find all files with a name matching favi* and display their properties:

Bash:

find . -name "favi*" -exec ls -l {} \;=

Downloading

Want the download a file? Just use:

Bash:

wget <url>

Here again thanks to Daniel.

Debian Aptitude

I had to use that to install missing packages while setting up TWiki on a Debian machine.

To show available packages:

Bash:

apt-cache show <pkg-name>

Where pkg-name is an exact package name

To display a list available packages containing a string in their name or description:

Bash:

apt-cache search <string>

To install a package:

Bash:

apt-get install <pkg-name>

To list installed packages:

Bash:

dpkg -l

Get the version of appach2 installed on your machine:

Bash:

dpkg -l | grep apache2

Symbolic link

To create a symbolic link with the same name as the original final in the current directory:

Bash:

ln -s /etc/apache2/mods-available/auth_ldap.load

Create an empty file

Just do:

Bash:

touch <filename>

To do deltree

Bash:

rm -rf <dirname>

Console text editor

Bad old Vi .
fte: I used it on a Debian it was ok but nothing exciting.
mc: Midnight Commander a clone of Norton Commander. It's rather good and does syntax highlighting for my Perl scripts.

Handle TGZ file

First deflate using gzip:

Bash:

gzip -d MyFile.tgz

Then using tar:

Bash:

tar -xf MyFile.tar

Memory information

Bash:

cat /proc/meminfo

Run all daily cron jobs

Bash:

for f in /etc/cron.daily/*; do echo $f; $f; done

Free disk space

Bash:

df -hl

df means diskfree
-h means human readable
-l means local disks only

Debian shell prompt

To display the working directory in your shell prompt:

Bash:

export PS1" \u@\h:\w\$"=
export PS1"\h:\w #"=

Send file through FTP

Do something like:

Bash:

scp ~/localdir/my.file user@example.com:~/ftpdir/my.file

Process status

See PS command.

Bash:

ps -Al

The column UID gives you the user ID for processes. To get the corresponding user name do

Bash:

cat /etc/passwd.

Kernel module

We are using the psmouse module as an example.
Get information about a module :

Bash:

modinfo psmouse

Remove a module :

Bash:

modprobe -r psmouse

Add a module :

Bash:

modprobe psmouse

Add a module with argument :

Bash:

modprobe psmouse proto=imps

List modules :

Bash:

lsmod

Date display

Try running:

Bash:

date -R