How to use multiple line comments in bash scripting

All single line comments in bash begin with # symbol, except for the first line (#!/bin/bash)
e.g.;

# this is an example of single line comment.

You can use HERE DOCUMENT feature to create multiple line comment

<<MULTILNCMNT
welcome to the go2linuxworld.blogspot.com
this is an example of
multiple line comment
in bash
MULTILNCMNT

How to debug a bash script in Linux

To debug a bash script, you need to run a shell script with -x option from the command line itself:

bash -x scriptname

or

bash -xv scriptname

You can also modify shebang line to run an entire script in debugging mode.

#!/bin/bash -x

echo "Hello ${USER}"

echo "Today is $(date)"

How to execute a scirpt in Linux

A shell script can be executed using the following syntax

chmod +x script.sh

./script.sh

You can also run the script directly without setting the script execute permission

bash script.sh

or
source script.sh
or

. script.sh

In the last example we are using . (dot) or source command which reads and executes commands from filename in the current shell.
When a script is executed using either the bash command or the source (.) command, you don't have to set execute permission on script.

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