Integer comparisons (-eq, -ne, -gt, -lt, -ge, -le) in Bash Scripting - Step-by-Step Execution

Concept Flow - Integer comparisons (-eq, -ne, -gt, -lt, -ge, -le)

Start

↓

Set two integers

↓

Choose comparison operator

↓

Compare integers

↓

True?

Yes→Execute True branch

↓

Execute False branch

↓

End

This flow shows how bash compares two integers using operators and executes code based on the comparison result.

Execution Sample

Bash Scripting

a=5
b=3
if [ $a -gt $b ]; then
  echo "a is greater"
else
  echo "a is not greater"
fi

This script compares two integers a and b and prints if a is greater than b.

Execution Table

Step	Variable a	Variable b	Condition	Result	Branch Taken	Output
1	5	3	5 -gt 3	True	True branch	a is greater
2	5	3	End of script	-	-	-

💡 Comparison 5 -gt 3 is True, so the True branch runs and script ends after output.

Variable Tracker

Variable	Start	After Step 1	Final
a	unset	5	5
b	unset	3	3

Key Moments - 3 Insights

Why do we use -gt instead of > in bash integer comparisons?

In bash, > is for string comparison or redirection, so integer comparisons use -gt, -lt, etc. as shown in the execution_table step 1.

What happens if variables are not integers?

If variables are not integers, the comparison fails or gives an error because -eq, -ne, -gt, -lt, -ge, -le expect integers, as seen in the condition column.

Why do we use square brackets [ ] around the condition?

Square brackets are a bash syntax for test command to evaluate conditions, as shown in the execution_sample code.

Visual Quiz - 3 Questions

Look at the execution_table step 1, what is the result of the condition '5 -gt 3'?

A False

B True

C Error

D Undefined

💡 Hint

Check the 'Result' column in execution_table row 1.

At which step does the script decide which branch to take?

A Step 2

B Before Step 1

C Step 1

D After Step 2

💡 Hint

Look at the 'Branch Taken' column in execution_table row 1.

If variable a was 2 instead of 5, what would be the output?

A a is not greater

B a is greater

C No output

D Error

💡 Hint

Compare the condition 'a -gt b' with a=2 and b=3 logically.

Concept Snapshot

Bash integer comparisons use operators: -eq (equal), -ne (not equal), -gt (greater than), -lt (less than), -ge (greater or equal), -le (less or equal).
Syntax: [ $a -gt $b ] inside if or test.
Returns true or false to control script flow.
Use only for integers, not strings.
Square brackets [ ] run the test command.
Example: if [ $a -eq $b ]; then ... fi

Full Transcript

This lesson shows how bash scripts compare integers using operators like -eq, -ne, -gt, -lt, -ge, and -le. The script sets two variables a and b, then uses an if statement with [ $a -gt $b ] to check if a is greater than b. If true, it prints 'a is greater'; otherwise, it prints 'a is not greater'. The execution table traces the condition evaluation and branch taken. Key points include using -gt instead of > for integers, square brackets for test, and ensuring variables hold integers. The visual quiz tests understanding of condition results, branch decisions, and output changes if variables change.