/bash-text-cmd

Command Line Tools Cheat Sheet

1. sed (Stream Editor)

  • Usage: Text substitution, filtering, and transformation.
  • Syntax: sed [options] 'command' file
  • Options:
    • -i: Edit files in-place.
    • -e: Multiple commands.
    • -n: Suppress automatic printing.
  • Examples:
    • Replace 'foo' with 'bar': sed -i 's/foo/bar/g' file.txt
    • Delete lines 2 to 5: sed '2,5d' file.txt
    • Print lines matching 'start' to 'end': sed -n '/start/,/end/p' file.txt
    • Append text after a line: sed '/pattern/a new line of text' file.txt

2. awk

  • Usage: Processing and analyzing text files.
  • Syntax: awk [options] 'program' file
  • Options:
    • -F: Field separator.
    • -v var=value: Set variable.
  • Examples:
    • Print the second column: awk '{print $2}' file.txt
    • Sum and average of first column: awk '{sum += $1} END {print "Sum:", sum, "Average:", sum/NR}' file.txt
    • Print lines where third column > 5: awk '$3 > 5' file.txt
    • Use comma as separator: awk -F, '{print $1}' file.csv

3. grep

  • Usage: Searching for text using patterns.
  • Syntax: grep [options] 'pattern' file
  • Options:
    • -i: Ignore case.
    • -r: Recursive search.
    • -l: List file names.
  • Examples:
    • Find 'pattern' in .txt files: grep 'pattern' *.txt
    • Case-insensitive search: grep -i 'pattern' file.txt
    • List files with 'pattern': grep -l 'pattern' *
    • Count 'pattern' occurrences: grep -c 'pattern' file.txt

4. jq

  • Usage: Parsing and transforming JSON.
  • Syntax: jq 'filter' [file]
  • Examples:
    • Extract "name" key: jq '.[] | .name' file.json
    • Filter objects by age > 30: jq '.[] | select(.age > 30)' file.json
    • Increase quantity by 1: jq '.items[] .quantity |= . + 1' file.json
    • Combine fields into new object: jq '{name: .name, total: .price * .quantity}' file.json

5. yq

  • Usage: YAML processing.
  • Syntax: yq [options] 'expression' [file]
  • Options:
    • -i: Update file in-place.
    • -o=json: Output as JSON.
  • Examples:
    • Extract value of key: yq e '.key' file.yaml
    • Update value: yq e '.key = "newValue"' -i file.yaml
    • Merge two YAML files: yq ea '. as $item ireduce ({}; . * $item )' file1.yaml file2.yaml
    • Convert YAML to JSON: yq e -o=json file.yaml

General Tips

  • Experiment safely: Test commands in a controlled environment.
  • Chain Commands: Combine tools using pipes (|) for complex workflows.
  • Regular Expressions: Utilize regex for advanced pattern matching.