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Deep Thought

Linux Exercise 5 - Finding Text in Files

Exercise: Searching and Filtering Text in Linux

Section titled “Exercise: Searching and Filtering Text in Linux”

Objective

Section titled “Objective”

Practice using grep, egrep, and related tools to search for patterns in files and directories. Learn to interpret results and document findings in a protocol.

Tasks

Section titled “Tasks”

Task 1: Search for Your User Information

Section titled “Task 1: Search for Your User Information”
  • Locate the line in /etc/passwd that contains your login details.
  • Expected outcome: You should find a single line with your username, UID, GID, home directory, and shell.

Task 2: Find Files Containing “hello”

Section titled “Task 2: Find Files Containing “hello””
  • Search the entire /home directory tree for files that contain the word hello.
  • Sort the results alphabetically by filename.
  • Expected outcome: A sorted list of file paths where the word appears.

Task 3: Filter locate Results

Section titled “Task 3: Filter locate Results”
  • Use locate to find all filenames containing the word emacs.
  • Exclude any results that contain the word lib.
  • Expected outcome: A filtered list of paths related to emacs but not libraries.
Section titled “Task 4: Case-Insensitive Search”
  • In your home directory, search all .txt files for lines containing the word error, ignoring case.
  • Expected outcome: Lines from text files that contain error in any case variation.

Task 5: Count Matches

Section titled “Task 5: Count Matches”
  • Count how many lines in /var/log (recursively) contain the word failed.
  • Expected outcome: A total number of matching lines across all log files.

Task 6: Invert Match

Section titled “Task 6: Invert Match”
  • In a chosen text file, display all lines that do not contain the word root.
  • Expected outcome: All lines except those mentioning root.

Task 7: Regular Expression Challenge

Section titled “Task 7: Regular Expression Challenge”
  • Create a file with at least 10 lines, some of which match this regex:
    (^[0-9]{1,5}[a-zA-Z ]+$)|none
  • Use egrep to test which lines match.
  • Expected outcome: Confirmation of which lines match and which do not.

Task 8: Recursive Search with Line Numbers

Section titled “Task 8: Recursive Search with Line Numbers”
  • Search recursively in /etc for lines starting with # (comments).
  • Display line numbers in the output.
  • Expected outcome: Lines from configuration files that are comments, with their line numbers.

Task 9: Top 10 Frequent Words

Section titled “Task 9: Top 10 Frequent Words”
  • In a large text file (e.g., /var/log/syslog), find the top 10 most frequent words.
  • Expected outcome: A list of words with their frequency counts, sorted from most to least frequent.

📑 Protocol (What to Hand In)

Section titled “📑 Protocol (What to Hand In)”

Each student must create a protocol (log) containing:

  • Command executed
  • Output received (full or partial if very long)
  • Explanation (1–2 sentences) of what the command did
  • Observation/interpretation of what they learned

Example:

Command: file sample.zip
Output: sample.zip: Zip archive data, at least v2.0 to extract
Explanation: Identified sample.zip as a compressed archive file.
Observation: Shows that zip files are binary and need archive tools to inspect contents.
Terminal window
Command: sudo tail -f /var/log/syslog
Output: (live log output appears)
Explanation: Monitors new log entries in real-time.
Observation: Useful for watching system activity as it happens.