Ternary operator in Bash

The ternary operator is a form of syntactic sugar for an in-line if/else statement. Many languages natively support the operator:

JavaScript:

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const color = 'blue';
console.log(color === 'blue' ? '🟦' : '🟩');
// Output: 🟦

Python:

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color = "blue"
print("🟦" if color == "blue" else "🟩")
# Output: 🟦

C:

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#include <stdio.h>
#include <string.h>

int main()
{
    char color[4] = "blue";
    printf("%s", (strcmp(color, "blue") == 0) ? "🟦" : "🟩");
}
// Output: 🟦

Ternary Operation

Bash does not have a native ternary operator. Instead, the same functionality can be achieved using:

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color="blue"
[[ "$color" == "blue" ]] && echo "🟦" || echo "🟩"
# Output: 🟦

[[ "$color" == "blue" ]] has an exit status of 0, so it evaluates the right expression of the && and echoes the blue emoji.

Similarly, if color="green", the [[ "$color" == "blue" ]] expression would have a nonzero exit status, so it evaluates the next logical statement (||) and echos the green emoji.

Saving to a variable

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color="blue"
emoji=$([[ "$color" == "blue" ]] && echo "🟦" || echo "🟩")
echo $emoji
# Output: 🟦

⚠️ Caution

If the right-hand side of the && condition has a nonzero exit status, it will silently default to the or (||) expression.

[[ cond ]] && op1 || op2 ➜ op2 will be selected if op1 fails.

Takeaway: Be mindful of the op1 operation. Ensure it exits with a 0 status code, or you may receive a false negative.