- 01Setting up (what you'll need)
- 02Your first shell script (echo)
- 03Using variables
- 04Command-line arguments ($1, $2 ...)
- 05Branching (the if statement)
- 06Repeating (the for loop)
- 07Repeating (the while loop)
- 08Writing your own function
- 09Working with arrays
- 10Command substitution ($())
- 11Working with strings (parameter expansion)
- 12Reading from standard input (read)
- 13Exit status and && / ||
- 14Pipes and redirection
- 15The case statement
- 16Arithmetic ($(( )))
- 17The basics of grep, sed and awk
- 18Argument checks and error handling
- 19Function return values and exit codes
- 20[Project] Build a small log-tallying script
The basics of grep, sed and awk
This lesson covers the basics of grep, sed, and awk — the three classic text-processing tools.
They have distinct jobs: grep finds the lines matching a pattern, sed replaces text, and awk pulls out columns and aggregates them.
The sample code extracts the error lines from several lines of log with grep "ERROR" and counts them with wc -l.
A common early stumble is knowing which of the three to reach for. "grep to find, sed to replace, awk to aggregate by column" is a rough rule that makes the choice easy.
In professional work, these three are very often chained together with pipes when investigating the cause of an incident across large log files.
๐งช This site can't compile or run Shell Script directly, so it checks on the spot whether what you typed matches the reference code (scoring happens entirely in your browser โ nothing is sent anywhere).