1. HOME
2. PDF

Contents

1 Links

1. sed useful commands http://www.catonmat.net/blog/wp-content/uploads/2008/09/ sed1line.txt
2. apt and dpkg cheat sheet http://www.cyberciti.biz/tips/linux-debian-package- management-cheat-sheet.html
3. scripting tutorial http://linuxconfig.org/bash-scripting-tutorial
4. http://www.cyberciti.biz/faq/linux-unix-bsd-xargs-construct-argument-lists- utility/ has good commands to learn from, on xargs
5. good hints on writing robust scripts http://www.davidpashley.com/articles/writing- robust-shell-scripts/

2 To use rsync for backup from 2 drives on windows from mounted shared folder using VBOX

Assuming /media/G and /media/E are 2 different shared folders mounted allready and you are now inside Linux in VBox then do

rsync -av  --delete /media/G /media/E

3 How to remove colors from terminal

alias ls='ls --color=never'

4 How to convert files in current folder from png to eps

  #!/bin/bash 
    for file in *.png; do 
             filename=${file%.*} 
             convert "$filename.png" "$filename.eps" 
    done

5 How to change extension of files in current folder

To change extension from .PNG to lowe case .png

 
#!/bin/bash 
for file in *.PNG; do 
    f=${file%.*} 
    mv "$f.PNG" "$f.png" 
done 

6 recusrive tree search for string in files

  grep -H -r "string I am searching for"  *

This should also work

 grep -H -r 'string I am searching for' *

also this

 find . -type f -exec grep -l 'string' {} \;

7 recusrive tree search for string in files with specific extension

 find . -name "*.txt" -print0 | xargs -0 egrep 'string'

8 recusrive tree search for string in files, where the string is at start of a line

 find . -name "*.txt" -exec egrep -l '^string' {} \;

9 recusrive tree search for string in files, print file name and the line with match

find . -type f -print0 | xargs -0 grep -H 'documentclass'

10 recusrive tree search for string in files, print file name only where match found

find . -type f -name *.tex -print0 | xargs -0 grep -l 'documentclass'

11 How to resize images in current folder based on width only

This example looks for all png files in current folder and will make thumbnails (shrink) any image that has a width larger than say 200 pixels. The height of the image is adjusted so that aspect ratio remain the same as originally was.

Edit as needed

#!/bin/bash 
shopt -s nullglob 
FILES=*.png 
for file in $FILES 
do 
     f=${file%.*} 
     echo "file is $file and f is $f" 
     convert "$f.png[200x>]" "$f"_thumb.png 
done

This example is as above except that the resizing is limited to enlarging the images to say 200 pixels. Edit as needed

Reference:

1. http://askubuntu.com/questions/135477/how-can-i-scale-all-images-in-a- folder-to-the-same-width
2. http://www.cyberciti.biz/faq/bash-loop-over-file/

12 How to find image width and height?

Can use the file command. But the ouptput has to be parsed. easier to use imageinfo

>sudo apt-get install imageinfo  #install if needed 
>w=`imageinfo --width foo.png` 
>echo $w 
81 
 
>h=`imageinfo --height foo.png` 
>echo $h 
24 

Reference:

1. http://stackoverflow.com/questions/4670013/fast-way-to-get-image- dimensions-not-filesize

13 How to resize animated gif file without losing the animation?

Useful trick to know

convert big.gif -coalesce coalesce.gif 
convert -size 200x100 coalesce.gif -resize 200x10 small.gif

reference: http://stackoverflow.com/questions/718491/resize-animated-gif-file-without-destroying-animation

14 How to batch convert all .png files to .jpg?

Thanks to http://www.turnkeylinux.org/blog/png-vs-jpg

apt-get install imagemagick 
 
#one file 
convert -flatten -background white file.png file.jpg 
 
#batch 
for f in *.png; do 
    n=$(echo $f|sed 's/.png/.jpg/'); 
    convert -flatten -background white $f $n 
done

15 How to install Linux on VBox

16 to use shared folders on a VBOX with Linux guest to windows

Make sure first the windows folder is added to shared folder in VBox settings for the VM. Then boot the VM. Now inside Linux create a mount point where to mount the shared folder to

>sudo mkdir /media/nabbasi 
>ls -l  /media 
drwxr-xr-x  2 root root 4096 Jun 22 17:02 nabbasi 
 
>cd /media 
>sudo chown -hR me:me nabbasi 
>ls -l 
drwxr-xr-x  2 me   me   4096 Jun 22 17:02 nabbasi

Now mount the shared folder, making sure it is owned by me

>sudo ./win_mount.sh 
>cat win_mount.sh 
mount -t vboxsf -o uid=1000,gid=1000 nabbasi /media/nabbasi

17 join AVI files to one

Thanks to http://www.torrent-invites.com/showthread.php?t=194756

18 How to change premissions recursive?

This will change all permissions on all files and folder

chmod -R 0755  folder_name

19 How to delete lines from file that starts with #?

This will change the file, backup is made to INPUT.txt.bak

sed -i.bak '/^#/d' INPUT.txt

20 How to search all tree and find file with specific name and then delete lines from this file that starts with #?

the -I {} is the marker, which says the file name is {}

find . -type f -name INPUT.txt -print0 | xargs -0 -I {}  sed -i.bak '/^#/d' {}

The above could also be done like this

find . -type f -name INPUT.txt -print0 | xargs -0 sed -i.bak '/^#/d'

But I found using explicit marker for the argument more clear. This is useful. If using a command that needs more than one argument, the marker is needed anyway, so might as well get used to using it. Marker can be anything. So this works also

find . -type f -name INPUT.txt -print0 | xargs -0 -I file  sed -i.bak '/^#/d' file

21 tree command

tree -n -L 1 --charset nwildner prints one level only and this tree -n -i -L 1 -d . does not print indentation lines

22 How copy selected files in one tree to another keeping same tree structure?

see http://unix.stackexchange.com/questions/83593/copy-specific-file-type-keeping-the-folder-structure

23 How to increase file handles limit for a process?

ulimit -n to find the limit, and to increase it to say 2048, type ulimit -S -n 2048

24 How to unzip a file using PHP on server?

Put this in a file foo.php and put it in the folder to unzip the file on the server and type the URL to this file

25 How to increase open file limit?

type unlimt -a to see all limits. To change open file limit, edit the file /etc/security/limits.conf as root and add these lines

* soft nofile 4096 
* hard nofile 4096

I rebooted after this just in case (may be reboot is not needed). Now it works. When I do

>ulimit -n 
4096

Reference: thanks to lornix answer

26 How to run sudo command without getting command not found error?

Use sudo -E env "PATH=$PATH"  command. Reference http://superuser.com/questions/709515/command-not-found-when-using-sudo

27 How to replace spaces in file names and folder with underscore?

find /tmp/ -depth -name "* *" -execdir rename 's/ /_/g' "{}" \;

Above is thanks to Dennis Williamson from http://stackoverflow.com/questions/2709458/bash-script-to-replace-spaces-in-file-names

Seems to work well.

28 How to convert DOS file to Unix?

tr -d '\015' < file.txt > new_file.txt

Just make sure not to use the same file above, else it will be wiped out.

http://stackoverflow.com/questions/2613800/how-to-convert-dos-windows-newline-crlf-to-unix-newline-n-in-bash-script

or just do sudo apt-get install dos2unix and type dos2unix foo.txt it will overwrite the file ok.

29 bulk file renaming in bash, to remove name with spaces, leaving trailing digits

Thanks to Avinash Raj, use this command rename 's/.*\s//' *.pdf see http://stackoverflow.com/questions/34469075/bulk-file-renaming-in-bash-to-remove-name-with-spaces-leaving-trailing-digits

30 How to convert djvu files to pdf?

Install sudo apt-get install djvulibre-bin. To convert multiple files, I wrote this small script

To convert one file, type dj2pdf  file.djvu and to convert multiple files, type dj2pdf  "*.djvu"

31 How to test the C compiler quickly?

32 How to delete files with some extension inside specific folder over tree?

thanks to Anderson M. Gomes http://unix.stackexchange.com/questions/270071/how-to-delete-all-files-with-specific-extension-in-specific-named-folders-in-lar

Here is the code

33 How to download a web page using wget?

An example,

34 How to delete folders inside tree with only specific name?

Answers thanks to https://stackoverflow.com/questions/13032701/how-to-remove-folders-with-a-certain-name

Or

35 How to delete files with specific names inside tree?

36 How to sort files in tree by date changed?

This will list all files in tree, showing date file changed with latest changed at bottom of listing shown.

Thanks to https://stackoverflow.com/questions/5566310/how-to-recursively-find-and-list-the-latest-modified-files-in-a-directory-with-s

37 How print longest line in file?

Thanks to Keith Thompson at https://unix.stackexchange.com/questions/24509/how-to-print-the-longest-line-in-a-file

38 How to change all spaces to underscore in folder names in tree?

Use

This will change all folder names below where it is issued and changes any space in the name to underscore.

39 apt useful commands

To just update a program to its latest without knowing the version number do, say want to update gfortran

 sudo apt-get upgrade gfortran

To update the distribution do

 sudo apt-get dist-upgrade

40 How to start a command after some time

To start a command after some time, say 30 minutes do sleep 30m &&  ./my_script 

To start a command after some time, say 2 hrs do sleep 2h &&  python ./script.py

The above can be canceled before the time elapses, and the command will not run.

41 How to mount shared windows folder from Linux guest using VMWARE?

This was very tricky. Here are the steps I did. This is on Linux Ubuntu as guest running inside the VMWare virtual machine with windows 7 as Host.

First I made sure shared folder is added when installing the guest OS in VMWare setup. Added "data" as my shared folder name.

After booting into Linux, did (as user called "me")

 
sudo apt-get install open-vm-tools open-vm-tools-desktop open-vm-tools-dkms 
cd /mnt 
sudo mkdir -p /mnt/hgfs/data 
sudo sudo chown -hR me:me data  #this sets me as owner. This is important 
vmhgfs-fuse .host:data /mnt/hgfs/data 

Do NOT use sudo in the last command above. When I did that, I got permission error.

42 How to make guest OS (windows) see USB devices on Linux Host

Make sure you are in vboxsers group

 sudo usermod -a -G vboxusers <useruame> 

logout and login. Now try to add USB 2.0 to VBox USB in settings of the window virtual machine. It should now be enabled.

43 How to remove a network disk in windows?

in windows DOS, type

net use G: /delete

Where G: is say the network disk

44 How to share folder using windows as guest and linux as host?

Made my /home/me/data/ as shared folder in VBox setting. So shared folder shows as data then.

Booted VBox windows 7. Then in windows typed in DOS

Type net use G: \\vboxsvr\data

So now it shows in windows as derive G

45 How to find files on linux?

sudo updatedb then locate file_name can also use find but locate is faster.

46 How to check is samba is running?

smbclient -L localhost if it asks for password, type it. It is then running.

47 How to see what printers are there in Linux?

lpstat -p

or do http://localhost:631/printers/ and select Printers from the menu. The above is CUSP interface.

48 How to extract first frame of animated gif file as png image?

convert 'moving_disk.gif[0]' moving_disk.png

49 How to change title of Linux termina?

Thanks to https://askubuntu.com/questions/22413/how-to-change-gnome-terminal-title type

PROMPT_COMMAND='echo -ne "\033]0;TITLE HERE\007"'

This will change the title in the terminal banner, normally located in the upper left corner.

To make the terminal title be the full path of the current folder, type

PROMPT_COMMAND='echo -ne "\033]0;$PWD\007"'

To make the terminal title be the last folder in full path of the current folder, type

PROMPT_COMMAND='echo -ne "\033]0;$(basename $(pwd))\007"'

50 How to slow down or speed up an existing animated gif file?

Thanks to http://blog.floriancargoet.com/slow-down-or-speed-up-a-gif-with-imagemagick/

identify -verbose your.gif  grep Delay| give current delay between each frame in 100’th of second. So it it say 50x100 then the delay is half second. To change the delay to one second between each frame do

convert -delay 100x100 your.gif your_slow.gif

So to make the time 0.25 second between each frame do

convert -delay 25x100 your.gif your_slow.gif

It looks like 6x100 is min time betweeb frames that browsers support. But this could depend on which browser.

51 Misc. useful linux commands

1.  cd - goes back to last directory
2.  reset clears and resets the terminal
3. if you type  apt update then want to do it again by adding sudo then no need to retype everything, just type  sudo !!  then the  !!  will copy the last command
4.  history followed by  !nn where nn is the command number show in history, will run that command
5. To run 2 commands one after the other, but stop if one fail, do  cmd1; cmd2; cmd3 The above will stop if one of these commands fail. If you use  cmd1&& cmd2&& cmd3 then it will not stop if one command fail. so using ; is more safe.
6.  command  column t| is useful command to format messy output into columns so easier to read

52 How to find files that changed before sometime ago?

use the command  find . -type f -mmin -150  to find files that changed within 150 minutes ago. And the command  find . -type f -mmin +150  to find files that changed longer than 150 minutes ago.