Bash Hybrid

This guide demonstrates how to combine the power of awk with Bash to process delimited text files. We’ll compare a pure awk script to a Bash/awk hybrid, then progressively build a reusable salary‐benchmarking tool.

Why Bash-AWK Hybrids?

• Pure awk scripts are concise for text processing.
• Embedding awk inside Bash adds flexibility (variables, flags, CLI args).
• Shebangs (#!/usr/bin/env …) let you run scripts directly.

Pure awk Script (salary.awk)

#!/usr/bin/env awk -f
BEGIN {
    FS = "|"
}
{
    print $2, $3
}

Bash Script Embedding awk (print_names.sh)

#!/usr/bin/env bash
awk -F "|" '{
    print $2, $3
}'

You can run either script by:

chmod +x print_names.sh
./print_names.sh < employees.txt

Or invoke awk directly:

awk -f salary.awk employees.txt

Preparing the Data Source

Our employees.txt file uses | as the field separator and contains:

Salary Thresholds

1. Basic One-Liner

Print first name, last name, and salary for every employee:

awk -F "|" '{ print $2, $3, $7 }' employees.txt

Output:

Kriti Shreshtha 60000
Rajasekar Vasudevan 75000
Debbie Miller 80000
Enrique Rivera 65000
Feng Lin 90000
Andy Luscomb 95000
Mark Crocker 85000
Jing Ma 100000

2. Filter by Salary Range

Use -v to pass thresholds into awk:

awk -F "|" \
    -v high_salary=90000 \
    -v low_salary=65000 \
    '$7 >= high_salary || $7 <= low_salary {
        print $2, $3, $7
    }' employees.txt

This shows both high and low earners in one stream.

3. Add a Header with BEGIN

Introduce a one-time header via BEGIN:

awk -F "|" \
    -v high_salary=90000 \
    -v low_salary=65000 \
    -v header="==== Salary Adjustments ====" \
    'BEGIN { print header }
     $7 >= high_salary || $7 <= low_salary {
         print $2, $3, $7
     }' employees.txt

4. Wrap into a Bash Script (salary.sh)

For readability and reuse, move the awk call into a Bash script:

#!/usr/bin/env bash

awk -F "|" \
  -v high_salary=90000 \
  -v low_salary=65000 \
  -v header="==== Salary Adjustments ====" '
BEGIN {
  print header
}
$7 >= high_salary || $7 <= low_salary {
  print $2, $3, $7
}
' < employees.txt

Make it executable and run:

chmod +x salary.sh
./salary.sh

5. Separate “Up” and “Down” Sections (salary-v2.sh)

Print distinct headers for high and low salaries:

#!/usr/bin/env bash

awk -F "|" \
  -v high_salary=90000 \
  -v low_salary=65000 \
  -v up_header="===== Needs to be adjusted up =====" \
  -v down_header="===== Needs to be adjusted down =====" '
$7 >= high_salary {
  print down_header
  print $2, $3, $7
}
$7 <= low_salary {
  print up_header
  print $2, $3, $7
}
' < employees.txt

6. One Header per Group (salary-v3.sh)

Use flags inside awk to avoid repeating headers:

#!/usr/bin/env bash

awk -F "|" \
  -v high_salary=90000 \
  -v low_salary=65000 \
  -v up_header="===== Needs to be adjusted up =====" \
  -v down_header="===== Needs to be adjusted down =====" '
$7 <= low_salary {
  if (!printed_up_header) {
    print up_header
    printed_up_header = 1
  }
  print $2, $3, $7
}
$7 >= high_salary {
  if (!printed_down_header) {
    print down_header
    printed_down_header = 1
  }
  print $2, $3, $7
}
' < employees.txt

7. Parameterize with CLI Arguments (salary-v4.sh)

Allow users to override thresholds when running the script:

#!/usr/bin/env bash

readonly UP_HEADER="===== Needs to be adjusted up ====="
readonly DOWN_HEADER="===== Needs to be adjusted down ====="

high_salary="${1:-90000}"
low_salary="${2:-65000}"

awk -F "|" \
  -v high_salary="$high_salary" \
  -v low_salary="$low_salary" \
  -v up_header="$UP_HEADER" \
  -v down_header="$DOWN_HEADER" '
$7 >= high_salary {
  if (!printed_down_header) {
    print down_header
    printed_down_header = 1
  }
  print $2, $3, $7
}
$7 <= low_salary {
  if (!printed_up_header) {
    print up_header
    printed_up_header = 1
  }
  print $2, $3, $7
}
' < employees.txt

Run with defaults:

chmod +x salary-v4.sh
./salary-v4.sh

Or specify custom thresholds:

./salary-v4.sh 80000 60000

Next Steps

You’ve now explored:

• Pure awk vs Bash/awk hybrids
• Using -v to pass variables into awk
• Conditional headers with BEGIN and internal flags
• Parameterizing scripts via CLI

Practice customizing these scripts for different file formats, field counts, or more complex filtering logic.

References

• GNU Awk User’s Guide
• Bash Reference Manual
• Advanced Bash-Scripting Guide