Perl One-Liners

Table of contents

1. About the Author
2. About the Technical Reviewer
3. Acknowledgments
4. 1. Introduction to Perl One-Liners
5. 2. Spacing
   1. 2.1 Double-space a file
   2. 2.2 Double-space a file, excluding the blank lines
   3. 2.3 Triple-space a file
   4. 2.4 N-space a file
   5. 2.5 Add a blank line before every line
   6. 2.6 Remove all blank lines
   7. 2.7 Remove all consecutive blank lines, leaving only one
   8. 2.8 Compress/expand all blank lines into N consecutive lines
   9. 2.9 Double-space between all words
   10. 2.10 Remove all spacing between words
   11. 2.11 Change all spacing between words to one space
   12. 2.12 Insert a space between all characters
6. 3. Numbering
   1. 3.1 Number all lines in a file
   2. 3.2 Number only non-empty lines in a file
   3. 3.3 Number and print only non-empty lines in a file (drop empty lines)
   4. 3.4 Number all lines but print line numbers only for non-empty lines
   5. 3.5 Number only lines that match a pattern; print others unmodified
   6. 3.6 Number and print only lines that match a pattern
   7. 3.7 Number all lines but print line numbers only for lines that match a pattern
   8. 3.8 Number all lines in a file using a custom format
   9. 3.9 Print the total number of lines in a file (emulate wc -l)
   10. 3.10 Print the number of non-empty lines in a file
   11. 3.11 Print the number of empty lines in a file
   12. 3.12 Print the number of lines in a file that match a pattern (emulate grep -c)
   13. 3.13 Number words across all lines
   14. 3.14 Number words on each individual line
   15. 3.15 Replace all words with their numeric positions
7. 4. Calculations
   1. 4.1 Check if a number is a prime
   2. 4.2 Print the sum of all fields on each line
   3. 4.3 Print the sum of all fields on all lines
   4. 4.4 Shuffle all fields on each line
   5. 4.5 Find the numerically smallest element (minimum element) on each line
   6. 4.6 Find the numerically smallest element (minimum element) over all lines
   7. 4.7 Find the numerically largest element (maximum element) on each line
   8. 4.8 Find the numerically largest element (maximum element) over all lines
   9. 4.9 Replace each field with its absolute value
   10. 4.10 Print the total number of fields on each line
   11. 4.11 Print the total number of fields on each line, followed by the line
   12. 4.12 Print the total number of fields on all lines
   13. 4.13 Print the total number of fields that match a pattern
   14. 4.14 Print the total number of lines that match a pattern
   15. 4.15 Print the number π
   16. 4.16 Print the number e
   17. 4.17 Print UNIX time (seconds since January 1, 1970, 00:00:00 UTC)
   18. 4.18 Print Greenwich Mean Time and local computer time
   19. 4.19 Print yesterday’s date
   20. 4.20 Print the date 14 months, 9 days, and 7 seconds ago
   21. 4.21 Calculate the factorial
   22. 4.22 Calculate the greatest common divisor
   23. 4.23 Calculate the least common multiple
   24. 4.24 Generate 10 random numbers between 5 and 15 (excluding 15)
   25. 4.25 Generate all permutations of a list
   26. 4.26 Generate the powerset
   27. 4.27 Convert an IP address to an unsigned integer
   28. 4.28 Convert an unsigned integer to an IP address
8. 5. Working With Arrays and Strings
   1. 5.1 Generate and print the alphabet
   2. 5.2 Generate and print all the strings from “a” to “zz”
   3. 5.3 Create a hex lookup table
   4. 5.4 Generate a random eight-character password
   5. 5.5 Create a string of specific length
   6. 5.6 Create an array from a string
   7. 5.7 Create a string from the command-line arguments
   8. 5.8 Find the numeric values for characters in a string
   9. 5.9 Convert a list of numeric ASCII values into a string
   10. 5.10 Generate an array with odd numbers from 1 to 100
   11. 5.11 Generate an array with even numbers from 1 to 100
   12. 5.12 Find the length of a string
   13. 5.13 Find the number of elements in an array
9. 6. Text Conversion and Substitution
   1. 6.1 ROT13 a string
   2. 6.2 Base64-encode a string
   3. 6.3 Base64-decode a string
   4. 6.4 URL-escape a string
   5. 6.5 URL-unescape a string
   6. 6.6 HTML-encode a string
   7. 6.7 HTML-decode a string
   8. 6.8 Convert all text to uppercase
   9. 6.9 Convert all text to lowercase
   10. 6.10 Uppercase only the first letter of each line
   11. 6.11 Invert the letter case
   12. 6.12 Title-case each line
   13. 6.13 Strip leading whitespace (spaces, tabs) from the beginning of each line
   14. 6.14 Strip trailing whitespace (spaces, tabs) from the end of each line
   15. 6.15 Strip whitespace (spaces, tabs) from the beginning and end of each line
   16. 6.16 Convert UNIX newlines to DOS/Windows newlines
   17. 6.17 Convert DOS/Windows newlines to UNIX newlines
   18. 6.18 Convert UNIX newlines to Mac newlines
   19. 6.19 Substitute (find and replace) “foo” with “bar” on each line
   20. 6.20 Substitute (find and replace) “foo” with “bar” on lines that match “baz”
   21. 6.21 Print paragraphs in reverse order
   22. 6.22 Print all lines in reverse order
   23. 6.23 Print columns in reverse order
10. 7. Selectively Printing and Deleting Lines
    1. 7.1 Print the first line of a file (emulate head -1)
    2. 7.2 Print the first 10 lines of a file (emulate head -10)
    3. 7.3 Print the last line of a file (emulate tail -1)
    4. 7.4 Print the last 10 lines of a file (emulate tail -10)
    5. 7.5 Print only lines that match a regular expression
    6. 7.6 Print only lines that do not match a regular expression
    7. 7.7 Print every line preceding a line that matches a regular expression
    8. 7.8 Print every line following a line that matches a regular expression
    9. 7.9 Print lines that match regular expressions AAA and BBB in any order
    10. 7.10 Print lines that don’t match regular expressions AAA and BBB
    11. 7.11 Print lines that match regular expression AAA followed by BBB followed by CCC
    12. 7.12 Print lines that are at least 80 characters long
    13. 7.13 Print lines that are fewer than 80 characters long
    14. 7.14 Print only line 13
    15. 7.15 Print all lines except line 27
    16. 7.16 Print only lines 13, 19, and 67
    17. 7.17 Print all lines from 17 to 30
    18. 7.18 Print all lines between two regular expressions (including the lines that match)
    19. 7.19 Print the longest line
    20. 7.20 Print the shortest line
    21. 7.21 Print all lines containing digits
    22. 7.22 Print all lines containing only digits
    23. 7.23 Print all lines containing only alphabetic characters
    24. 7.24 Print every second line
    25. 7.25 Print every second line, beginning with the second line
    26. 7.26 Print all repeated lines only once
    27. 7.27 Print all unique lines
11. 8. Useful Regular Expressions
    1. 8.1 Match something that looks like an IP address
    2. 8.2 Test whether a number is in the range 0 to 255
    3. 8.3 Match an IP address
    4. 8.4 Check whether a string looks like an email address
    5. 8.5 Check whether a string is a number
    6. 8.6 Check whether a word appears in a string twice
    7. 8.7 Increase all integers in a string by one
    8. 8.8 Extract the HTTP User-Agent string from HTTP headers
    9. 8.9 Match printable ASCII characters
    10. 8.10 Extract text between two HTML tags
    11. 8.11 Replace all <b> tags with <strong>
    12. 8.12 Extract all matches from a regular expression
12. A. Perl’s Special Variables
    1. A.1 Variable $_
       1. Using $_ with the -n argument
       2. Using $_ with the -p argument
       3. Using $_ explicitly
    2. A.2 Variable $.
    3. A.3 Variable $/
    4. A.4 Variable $\
    5. A.5 Variables $1, $2, $3, and so on
    6. A.6 Variable $,
    7. A.7 Variable $”
    8. A.8 Variable @F
    9. A.9 Variable @ARGV
    10. A.10 Variable %ENV
13. B. Using Perl One-Liners On Windows
    1. B.1 Perl on Windows
    2. B.2 Bash on Windows
    3. B.3 Perl One-Liners in Windows Bash
    4. B.4 Perl One-Liners in the Windows Command Prompt
       1. Converting One-Liners in the Windows Command Prompt
       2. Symbol Challenges
       3. Windows File Paths
    5. B.5 Perl One-Liners in PowerShell
       1. Converting One-Liners in PowerShell
       2. One-Liners in PowerShell 3.0+
14. C. Perl1Line.Txt
    1. C.1 Spacing
       1.  
          1. Double-space a file
          2. Double-space a file, excluding the blank lines
          3. Triple-space a file
          4. N-space a file
          5. Add a blank line before every line
          6. Remove all blank lines
          7. Remove all consecutive blank lines, leaving only one
          8. Compress/expand all blank lines into N consecutive lines
          9. Double-space between all words
          10. Remove all spacing between words
          11. Change all spacing between words to one space
          12. Insert a space between all characters
    2. C.2 Numbering
       1.  
          1. Number all lines in a file
          2. Number only non-empty lines in a file
          3. Number and print only non-empty lines in a file (drop empty lines)
          4. Number all lines but print line numbers only for non-empty lines
          5. Number only lines that match a pattern; print others unmodified
          6. Number and print only lines that match a pattern
          7. Number all lines but print line numbers only for lines that match a pattern
          8. Number all lines in a file using a custom format
          9. Print the total number of lines in a file (emulate wc -l)
          10. Print the number of non-empty lines in a file
          11. Print the number of empty lines in a file
          12. Print the number of lines in a file that match a pattern (emulate grep -c)
          13. Number words across all lines
          14. Number words on each individual line
          15. Replace all words with their numeric positions
    3. C.3 Calculations
       1.  
          1. Check if a number is a prime
          2. Print the sum of all fields on each line
          3. Print the sum of all fields on all lines
          4. Shuffle all fields on each line
          5. Find the numerically smallest element (minimum element) on each line
          6. Find the numerically smallest element (minimum element) over all lines
          7. Find the numerically largest element (maximum element) on each line
          8. Find the numerically largest element (maximum element) over all lines
          9. Replace each field with its absolute value
          10. Print the total number of fields on each line
          11. Print the total number of fields on each line, followed by the line
          12. Print the total number of fields on all lines
          13. Print the total number of fields that match a pattern
          14. Print the total number of lines that match a pattern
          15. Print the number π
          16. Print the number e
          17. Print UNIX time (seconds since January 1, 1970, 00:00:00 UTC)
          18. Print Greenwich Mean Time and local computer time
          19. Print yesterday’s date
          20. Print the date 14 months, 9 days, and 7 seconds ago
          21. Calculate the factorial
          22. Calculate the greatest common divisor
          23. Calculate the least common multiple
          24. Generate 10 random numbers between 5 and 15 (excluding 15)
          25. Generate all permutations of a list
          26. Generate the powerset
          27. Convert an IP address to an unsigned integer
          28. Convert an unsigned integer to an IP address
    4. C.4 Working with Arrays and Strings
       1.  
          1. Generate and print the alphabet
          2. Generate and print all the strings from “a” to “zz”
          3. Create a hex lookup table
          4. Generate a random eight-character password
          5. Create a string of specific length
          6. Create an array from a string
          7. Create a string from the command-line arguments
          8. Find the numeric values for characters in a string
          9. Convert a list of numeric ASCII values into a string
          10. Generate an array with odd numbers from 1 to 100
          11. Generate an array with even numbers from 1 to 100
          12. Find the length of a string
          13. Find the number of elements in an array
    5. C.5 Text Conversion and Substitution
       1.  
          1. ROT13 a string
          2. Base64-encode a string
          3. Base64-decode a string
          4. URL-escape a string
          5. URL-unescape a string
          6. HTML-encode a string
          7. HTML-decode a string
          8. Convert all text to uppercase
          9. Convert all text to lowercase
          10. Uppercase only the first letter of each line
          11. Invert the letter case
          12. Title-case each line
          13. Strip leading whitespace (spaces, tabs) from the beginning of each line
          14. Strip trailing whitespace (spaces, tabs) from the end of each line
          15. Strip whitespace (spaces, tabs) from the beginning and end of each line
          16. Convert UNIX newlines to DOS/Windows newlines
          17. Convert DOS/Windows newlines to UNIX newlines
          18. Convert UNIX newlines to Mac newlines
          19. Substitute (find and replace) “foo” with “bar” on each line
          20. Substitute (find and replace) “foo” with “bar” on lines that match “baz”
          21. Print paragraphs in reverse order
          22. Print all lines in reverse order
          23. Print columns in reverse order
    6. C.6 Selectively Printing and Deleting Lines
       1.  
          1. Print the first line of a file (emulate head -1)
          2. Print the first 10 lines of a file (emulate head -10)
          3. Print the last line of a file (emulate tail -1)
          4. Print the last 10 lines of a file (emulate tail -10)
          5. Print only lines that match a regular expression
          6. Print only lines that do not match a regular expression
          7. Print every line preceding a line that matches a regular expression
          8. Print every line following a line that matches a regular expression
          9. Print lines that match regular expressions AAA and BBB in any order
          10. Print lines that don’t match regular expressions AAA and BBB
          11. Print lines that match regular expression AAA followed by BBB followed by CCC
          12. Print lines that are at least 80 characters long
          13. Print lines that are fewer than 80 characters long
          14. Print only line 13
          15. Print all lines except line 27
          16. Print only lines 13, 19, and 67
          17. Print all lines from 17 to 30
          18. Print all lines between two regular expressions (including the lines that match)
          19. Print the longest line
          20. Print the shortest line
          21. Print all lines containing digits
          22. Print all lines containing only digits
          23. Print all lines containing only alphabetic characters
          24. Print every second line
          25. Print every second line, beginning with the second line
          26. Print all repeated lines only once
          27. Print all unique lines
    7. C.7 Useful Regular Expressions
       1.  
          1. Match something that looks like an IP address
          2. Test whether a number is in the range 0 to 255
          3. Match an IP address
          4. Check whether a string looks like an email address
          5. Check whether a string is a number
          6. Check whether a word appears in a string twice
          7. Increase all integers in a string by one
          8. Extract the HTTP User-Agent string from HTTP headers
          9. Match printable ASCII characters
          10. Extract text between two HTML tags
          11. Replace all <b> tags with <strong>
          12. Extract all matches from a regular expression
15. Index
16. About the Author
17. Copyright