refs:

• Tutorialspointhttps://www.tutorialspoint.com/awk/awk_overview.htm)
• man page of gawk

# Overview

AWK is created by Alfred Aho, Peter Weinberger and Brian Kernghan from AT & T lab.

GAWK is the GNU distribution of AWK.

awk is a pattern scanning and processing language.

The routine of AWK:

1. AWK reads a line from input stream and stores it in memory.
2. All AWK commands are applied sequentially on the input.
3. Repeat until the file reaches end.

# Structure:

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BEGIN{commands}

/pattern/{commands}

END{commands}

1. The BEGIN block is excuted at start-up only once (this block is optional)
2. The second block is the body block, which is applied on each input line.
3. END Block is like BEGIN, but excuted at the end.

# Command Line:

awk -f command.awk file.txt

# Examples: