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Linux CLI HowTo 11 🐧 whatis, info and apropos commands

1. How to get brief descriptions of commands

Steps:

  1. Open terminal
  2. Type whatis command_name
  3. Press Enter
  4. Example: whatis ls shows “ls – list directory contents”

2. How to check multiple commands at once

Steps:

  1. Open terminal
  2. Type whatis command1 command2 command3
  3. Press Enter
  4. Example: whatis cp mv rm shows descriptions for all three commands

3. How to use wildcard search with whatis

Steps:

  1. Open terminal
  2. Type whatis -w 'pattern'
  3. Press Enter
  4. Example: whatis -w 'mv*' finds all commands starting with “mv”

4. How to use regex search with whatis

Steps:

  1. Open terminal
  2. Type whatis -r 'regex_pattern'
  3. Press Enter
  4. Example: whatis -r 'mv[ab]+' finds commands matching the pattern

5. How to update the whatis database

Steps:

  1. Open terminal
  2. Type sudo makewhatis
  3. Press Enter
  4. Wait for completion (may take several minutes)
  5. This updates the manual page database after installing new commands

6. How to search for commands by keyword

Steps:

  1. Open terminal
  2. Type apropos keyword
  3. Press Enter
  4. Example: apropos directory finds all commands related to directories

7. How to search for multiple keywords

Steps:

  1. Open terminal
  2. Type apropos "keyword1 keyword2"
  3. Press Enter
  4. Example: apropos "remove file" searches for commands that mention both remove and file

8. How to use wildcard search with apropos

Steps:

  1. Open terminal
  2. Type apropos -w 'pattern'
  3. Press Enter
  4. Example: apropos -w 'mv*' finds all commands starting with “mv”

9. How to use regex search with apropos

Steps:

  1. Open terminal
  2. Type apropos -r 'regex_pattern'
  3. Press Enter
  4. Example: apropos -r 'mv[ab]+' finds commands matching the pattern

10. How to search in specific manual sections

Steps:

  1. Open terminal
  2. Type apropos -s section_numbers keyword
  3. Press Enter
  4. Example: apropos -s 1,2 directory searches only in sections 1 and 2 of manuals

11. How to require all keywords to be present

Steps:

  1. Open terminal
  2. Type apropos -a keyword1 keyword2
  3. Press Enter
  4. Example: apropos -a remove directory finds commands containing both “remove” and “directory”

12. How to get detailed information about a command

Steps:

  1. Open terminal
  2. Type info command_name
  3. Press Enter
  4. Example: info cp shows comprehensive help for the cp command

13. How to search for commands in info documentation

Steps:

  1. Open terminal
  2. Type info -k keyword
  3. Press Enter
  4. Example: info -k "copy" finds all commands related to copying

14. How to navigate info documentation

Steps:

  1. Open info help (like info cp)
  2. Use these navigation keys:
  • Space: scroll forward one page
  • Backspace: scroll backward one page
  • n: move to next node
  • p: move to previous node
  • u: go up one level
  • Enter: follow a link to another section
  • q: quit info and return to terminal

15. How to specify a particular info file

Steps:

  1. Open terminal
  2. Type info -f filename
  3. Press Enter
  4. Example: info -f cp specifies the cp info file directly

16. How to Find file manipulation commands

Steps:

  1. Use apropos to find related commands: apropos file
  2. Check specific commands with whatis: whatis cp mv rm
  3. Get detailed info on important commands: info cp

17. How to Search for commands after installation

Steps:

  1. After installing new software, run: sudo makewhatis
  2. Search for the new commands: whatis command_name
  3. Get detailed information: info command_name

18. How to Find commands by partial names

Steps:

  1. Use wildcard search: apropos -w 'mv*'
  2. Use regex search: whatis -r 'mv[ab]+'
  3. Combine with other options for precise results

19. When to use whatis vs apropos

  • Use whatis when you know the exact command name
  • Use apropos when you want to search by keywords or description

20. apropos, whatis, info common parameter combinations

  • apropos -r 'pattern' -s 1,2 for regex search in specific sections
  • whatis -w '*' to see all available commands with descriptions
  • info -k 'keyword' to find related info documentation

21. Navigation shortcuts reminder

  • Space and Backspace: scroll through pages
  • n/p: move between nodes
  • u: go up a level
  • Enter: follow links
  • q: quit cleanly

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