mjhjmtu

I want Output of this file only

AVDDPLL1V8
AGNDPLL1V8
DVDDPLL1V1
DGNDPLL1V1 

Here is my input:

6.1.2 Power and Ground Pins
 The following table describes the power and ground pins for the PLL.


 Table 5: Power and Ground Pins
 Pin Name Description
 Analog power pin. This pin provides the power supply for the sensitive analog
 AVDDPLL1V8
 blocks of the PLL.
 Analog ground pin. This pin provides the ground for the sensitive analog blocks
 AGNDPLL1V8
 of the PLL.
 Digital power pin. This pin provides power supply for the digital circuits in the
 DVDDPLL1V1
 PLL.
 DGNDPLL1V1 Digital ground pin. This pin provides ground for the digital circuits in the PLL.

sed -n 's/^ *([[:upper:]0-9]10,).*/1/p'

That will print the first word on a line if the word is comprised of at least 10 consecutive characters that are only uppercase letters and/or numbers. Nothing else is printed.

Run on your example data its output is:

AVDDPLL1V8
AGNDPLL1V8
DVDDPLL1V1
DGNDPLL1V1

One way to do it:

$ awk '$1 ~ /^[[:upper:]]+[0-9]+/ print $1' file
AVDDPLL1V8
AGNDPLL1V8
DVDDPLL1V1
DGNDPLL1V1

Explanation

We only check first field of each line, if it start with ^ one or more uppercase characters [[:upper:]]+, follow by one or more numbers [0-9]+, just print it.

With your input, I assume that after uppercase characters is one ore more numbers.

Try the below grep command to print all the alphanumeric characters,

$ grep -oP '[A-Z0-9]*[A-Z][0-9][A-Z0-9]*' file
AVDDPLL1V8
AGNDPLL1V8
DVDDPLL1V1
DGNDPLL1V1

If your problem with the existing answers is
that they don’t find words that consist only of capital letters (with no digits),
then we can adapt Gnouc’s answer like this:

awk '$1 ~ /^[[:upper:]0-9]+$/ print $1'

or

awk '$1 ~ /^[[:upper:][:digit:]]+$/ print $1'

This differs from his solution in that

• By putting the digits ([0-9] or [:digit:]) into the brackets
  with the capital letters ([:upper:]), we require only that each matching character
  is either a capital letter or a digit,
  where Gnouc’s current answer requires at least one of each.


• By adding the $, we make sure that the entire first word
  is composed of capital letters and/or digits. 
  Without it, The, Table, Pin, and Analog would match
  because they begin with a capital letter.

This would match a plain number (e.g., 612)
if it is the first “word” (i.e., the first sequence of non-blank characters) on a line.
To avoid this, do

awk '$1 ~ /^[[:upper:]][[:upper:]0-9]*$/ print $1'

or

awk '$1 ~ /^[[:upper:]][[:upper:][:digit:]]*$/ print $1'

which require the “word” to begin with a letter.