read -p "confirm [y/N]: " -r
if [[ ! $REPLY =~ ^[Yy]$ ]]; then
    exit 1
fi

stackoverflow

You can use these ANSI escape codes:

Black        0;30     Dark Gray     1;30
Red          0;31     Light Red     1;31
Green        0;32     Light Green   1;32
Brown/Orange 0;33     Yellow        1;33
Blue         0;34     Light Blue    1;34
Purple       0;35     Light Purple  1;35
Cyan         0;36     Light Cyan    1;36
Light Gray   0;37     White         1;37

And then use them like this in your script:

RED='\033[0;31m'
NC='\033[0m' # No Color
printf "I ${RED}love${NC} Stack Overflow\n"

which prints love in red.

stackoverflow

It is very easy to compress a Whole Linux/UNIX directory. It is useful to backup files, email all files, or even to send software you have created to friends. Technically, it is called as a compressed archive. GNU tar command is best for this work. It can be use on remote Linux or UNIX server. It does two things for you:

• Create the archive
• Compress the archive

You need to use the tar command as follows (syntax of tar command):

tar -zcvf archive-name.tar.gz directory-name

Where:

• -z Compress archive using gzip program
• -c Create archive
• -v Verbose i.e display progress while creating archive
• -f Archive File name

For example, say you have a directory called /home/jerry/prog and you would like to compress this directory then you can type tar command as follow:

$ tar -zcvf prog-1-jan-2005.tar.gz /home/jerry/prog

Above command will create an archive file called prog-1-jan-2005.tar.gz in current directory. If you wish to restore your archive then you need to use the following command (it will extract all files in current directory):

$ tar -zxvf prog-1-jan-2005.tar.gz

Where:

• -x Extract files

If you wish to extract files in particular directory, for example in /tmp then you need to use the following command:

$ tar -zxvf prog-1-jan-2005.tar.gz -C /tmp
$ cd /tmp
$ ls -

A note about non gnu/tar command

The above syntax use GNU tar command for compressing and uncompressing tar files. If your system does not use GNU tar, you can still create a compressed tar file, via the following syntax:

tar -cvf - file1 file2 dir3 | gzip > archive.tar.gz

cyberciti

Execute Command A, then execute Command B (no evaluation of anything)

Command A & Command B

Execute Command A, and redirect all its output into the input of Command B

Command A | Command B

Execute Command A, evaluate the errorlevel after running and if the exit code (errorlevel) is 0, only then execute Command B

Command A && Command B

Execute Command A, evaluate the exit code of this command and if it's anything but 0, only then execute Command B

Command A || Command B

If you want to truncate/zero a log file to which you don't have write access, you can do:

sudo truncate -s0 logfile

serverfault

Optionally you can backup the log file put the current date in the file name and then truncate it. You can do this with this simple command:

tar -zcvf $(date +"%y-%m-%d")"_file.tar.gz" file.log && truncate -s0 file.log

...output example: 16-01-14_test.tar.gz