history

  • Description: Displays a list of previously executed commands in the terminal session.

  • Example usage:

    history

Note: You can reuse specific commands using ! followed by the command’s sequence number from the history output. For example, !3 will re-run the command at sequence number 3.

grep

  • Description: Searches for text patterns within files.

  • Example usage:

    grep "sample" sample.txt # search for the term "sample" within sample.txt
grep -i "error" /var/log/dpkg.log # The `grep` command with the `-i` option searches case-insensitively for the term "error" within the /var/log/dpkg.log file.

Note: While these examples showcase the basics of usage of a command, these tools are more sophisticated.

  • For instance, if you forget which file contains specific information (e.g., a list of fruits), grep with the -r flag allows searching through directories and subdirectories to quickly locate the elusive content.

    grep -r "apple" . # -r performs a recursive search within the current directory and all of its subdirectories.
grep -r -w "apple" . # -w matches whole words only.

find

  • Description: Searches for files and directories within a specified directory hierarchy.

  • Example usage:

    find . -type f -name "*.txt" # search for all .txt files within the current directory (.)

sort

  • Description: Sorts lines of text files alphabetically or numerically.

  • Example usage:

    sort data.txt # Sorting lines in alphabetical order.
sort -rn numbers.txt # Sorting lines in reverse numerical order.

shuf

  • Description: Shuffles lines of text randomly.

  • Example usage:

    shuf playlist.txt # Shuffling lines in a file named `playlist.txt`
shuf -n 1 quotes.txt # Selecting a random line from `quotes.txt`

uniq

  • Description: Filters and displays adjacent matching lines in a file, showing only unique lines.

  • Example usage:

    uniq data.txt # Removing adjacent duplicate lines from `file.txt`
uniq -c data.txt # Displaying only unique lines along with the count of occurrences

sed

  • Description: sed stands for “stream editor” and is a powerful command-line tool for manipulating text in Linux. It can perform a variety of text editing operations, including searching, replacing, inserting, and deleting text.

  • Example usage:

    sed 's/old_text/new_text/' content.txt # Substituting text in a file named `content.txt`
sed `s/apple/orange/` fruits.txt # Searches for the word ”apple” in the file ”fruits.txt” and replaces it with the word ”orange”
sed -i `s/apple/orange/` fruits.txt # -i to disable case sensetive
sed '/pattern/d' data.txt # Deleting lines matching a pattern from `data.txt`

cut

  • Description: Extracts specific portions (columns) of lines from files.

  • Example usage:

    cut -d ':' -f 1 data.txt # Extracting the first column (delimited by `:`) from a file named `data.txt`
cut -c 3-7 names.txt # Extracting characters 3 to 7 from each line in a file named `names.txt`