Script Utilities and Variables

Cybersecurity Linux Lesson 3.1.3

Common Script Utilities

  • awk scans files for specific patterns and extracts information based on those patterns
  • sed (stream editor) is designed for efficiently processing and transforming text streams
    • Allows for search and replace, insertion, deletion, etc.
  • find searches files and directories in a directory hierarchy
  • xargs takes inputs from a pipe or file and converts it into arguments for a specified command

Additional Common Script Utilities

  • grep is used for searching patterns within text files
  • egrep/grep -E supports extended regular expressions
  • tee reads standard input and writes to both standard output and files simultaneously
  • wc (Word Count) counts lines, words, and characters in a file or input stream
  • cut extracts specific fields from each line of a file

Remaining Common Script Utilities

  • tr translates or deletes characters in a stream of data
  • head displays the first few lines of a file
  • tail displays the last few lines of a file

Environment Variables and Paths

  • $PATH specifies a colon-separated list of directories where the system looks for executable programs
  • $SHELL points to the user’s default shell
  • $? Represents the exit status of the last executed command
    • 0 typically indicates success while non-zeros indicate errors or specific exit statuses

Environment Variables and Paths

  • What does this command do:
    echo $PATH | tr ':' '\n' | awk -F/ '{ print $NF }' | uniq

Relative and Absolute Paths

  • Relative paths describe the location of a file or directory in relation to the current working directory
    • Useful for navigating within the file system without specifying the full path
    • E.g. ./file
  • Absolute paths specify the complete path from the root directory to a file or directory
    • Provides an unambiguous reference
    • E.g. /home/user/file