Sort, Cut, Sed options

Question 1

What does sort -n do?

Answer 1

• Performs numeric sort instead of alphabetical sort
• Treats numbers as actual values rather than strings

Example: sort -n numbers.txt sorts 10 before 2 (unlike default alphabetical)

Question 2

How does sort -r change the output?

Answer 2

• Reverses the sort order (descending instead of ascending)
• Can be combined with other options like sort -nr for reverse numeric sort

Useful for finding largest values or reverse alphabetical order

Question 3

What is the purpose of sort -u?

Answer 3

• Removes duplicate lines while sorting (unique sort)
• Combines sorting and deduplication in one operation

More efficient than using sort | uniq separately

Question 4

When would you use sort -k?

Answer 4

• Sorts by a specific field/column number
• Example: sort -k2 file.txt sorts by the second field
• Essential for sorting structured data like CSV files

Question 5

What does sort -t accomplish?

Answer 5

• Specifies field delimiter/separator character
• Default is whitespace, but -t allows custom delimiters

Example: sort -t: -k3 /etc/passwd sorts by third field using colon delimiter

Question 6

How does sort -f affect sorting?

Answer 6

• Performs case-insensitive sorting (fold case)
• Treats uppercase and lowercase letters as equivalent

Prevents sorting issues where uppercase letters come before lowercase

Question 7

What does cut -d specify?

Answer 7

• Sets the delimiter character for field separation
• Default delimiter is tab, -d allows custom delimiters

Example: cut -d: -f1 /etc/passwd uses colon as delimiter

Question 8

How does cut -f work?

Answer 8

• Selects specific fields/columns by number
• Can specify ranges like -f1-3 or multiple fields like -f1,3,5

Must be used with delimited data (requires -d for custom delimiters)

Question 9

What is cut -c used for?

Answer 9

• Cuts by character positions instead of fields

Example: cut -c1-10 file.txt extracts first 10 characters of each line
* Useful for fixed-width data or extracting specific character ranges

Question 10

When would you use cut -b?

Answer 10

• Cuts by byte positions (important for multi-byte characters)
• Similar to -c but handles UTF-8 and other multi-byte encodings correctly

Essential for international text processing

Question 11

What does cut –complement do?

Answer 11

• Inverts the selection - shows everything except specified fields/characters

Example: cut -d: –complement -f3 shows all fields except the third
* Opposite of normal cut behavior

Question 12

What does sed ‘s/old/new/’ do?

Answer 12

• Substitutes first occurrence of ‘old’ with ‘new’ on each line
• Basic find-and-replace operation in sed

Only replaces first match per line unless global flag is used

Question 13

How does sed ‘s/old/new/g’ differ from sed ‘s/old/new/’?

Answer 13

• Global flag (g) replaces all occurrences on each line, not just the first
• Without g, only first match per line is replaced

Essential for complete text replacement operations

Question 14

What is sed -i used for?

Answer 14

• In-place editing - modifies the original file directly
• Without -i, sed outputs to stdout and leaves original unchanged

Dangerous option - always backup files before using sed -i

Question 15

How does sed -n work with p command?

Answer 15

• Suppresses automatic printing of lines (-n) and p prints specific lines

Example: sed -n ‘5p’ file.txt prints only line 5
* Commonly used for extracting specific lines from files

Question 16

What does sed ‘/pattern/d’ accomplish?

Answer 16

• Deletes lines that match the specified pattern

Example: sed ‘/^#/d’ file.txt removes all lines starting with #
* Useful for removing comments or unwanted content

Question 17

When would you use sed ‘s/old/new/I’?

Answer 17

• Case-insensitive substitution using the I flag
• Matches pattern regardless of upper/lowercase

Example: sed ‘s/error/ERROR/I’ matches ‘Error’, ‘ERROR’, ‘error’