Linux - set -vx

Set command in Linux is used to set or unset values of shell options and positional parameters.

It has many useful options, and specifically, set -vx is very useful to debug a Linux script.

-v  Print shell input lines as they are read.
-x  Print commands and their arguments as they are executed.

To use this, simply put set -vx before an interested script line. Usually, I will put it at the top of my script to print out everything.

For example, you can use set -vx as follow script call test.sh

#!/bin/bash
set -vx
export foo=$1
echo $foo 

Executing the test.sh with

./test.sh hello

The output will be

export foo=$1
+ export foo=hello
+ foo=hello
echo $foo
+ echo hello
hello

Those line with + sign are evaluated value during execution

Reference: http://linuxcommand.org/lc3_man_pages/seth.html