- 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
Branching (the if statement)
This lesson covers how to write an if statement in a shell script.
You branch with if [ condition ]; then ... elif [ condition ]; then ... else ... fi. Note that spaces are required both inside and outside the square brackets [ ].
The sample code uses if / elif / else to print one of three messages depending on score. Numeric comparison uses special operators such as -ge (greater than or equal).
A common early stumble is the spacing around the brackets in [ $score -ge 80 ]. Squeezing it up as [$score-ge 80] is an error.
In professional work, if statements come up constantly for checking whether a file exists and for branching on the result of a command.
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).