Bash if else and elif: if then else, conditions, and `[[` vs `[`

This lesson sits in the Shell Scripting & Bash course hub if you want the full sequence.

Almost every script uses bash if else style branching: run a test or command, and pick a block based on its exit status. You will see the same idea under names like if else bash, bash if then else, or else if bash—in the shell the second keyword is elif, not else if. This page covers the grammar (if / then / else / fi), elif chains and why order matters, and how this ties to string and number comparisons, plus where [[ differs from [. Use it with for, while, and functions when if sits inside larger control flow. When one variable must match many fixed strings (for example $1 is start or stop), Bash case statement is often clearer than a long elif chain.

Tested all the commands and code from this article on Ubuntu 25.04, kernel 6.14.0-37-generic, Bash 5.2.37.

Exit status: what if actually tests

if looks at the exit code of the list that follows it. 0 means success (true), any non-zero value means failure (false). [[ … ]] and [ … ] are commands that return 0 or 1; normal commands like grep or test -f work the same way.

if … then … fi (no else)

VAR1=10
VAR2=5

if [[ "$VAR1" -ge "$VAR2" ]]; then
  echo "$VAR2 is less than or equal to $VAR1"
fi

Output:

5 is less than or equal to 10

One-line form (use sparingly for readability):

VAR1=10 VAR2=5; if [[ "$VAR1" -ge "$VAR2" ]]; then echo "ok"; fi

Output:

ok

if … then … else … fi (classic bash if else)

VAR1=10
VAR2=50

if [[ "$VAR1" -ge "$VAR2" ]]; then
  echo "first branch"
else
  echo "else branch"
fi

Output:

else branch

The else branch runs when the test returns non-zero.

elif chains (else if bash → write elif)

x=2

if [[ "$x" -eq 1 ]]; then
  echo "one"
elif [[ "$x" -eq 2 ]]; then
  echo "two"
else
  echo "other"
fi

Output:

two

Order matters

Conditions are evaluated top to bottom; the first match wins. If the first test is too broad, later elif lines never run:

a=10
b=10

if [[ "$a" -ge "$b" ]]; then
  echo "first: greater-or-equal"
elif [[ "$a" -eq "$b" ]]; then
  echo "second: equal"
fi

Output:

first: greater-or-equal

For equality-only logic, test -eq (or string ==) before broader -ge checks, or split into clearer branches.

[[ … ]] vs [ … ]

• [[ is a Bash keyword with friendlier parsing (often fewer backslashes, safer default handling of empty variables).
• [ is the test builtin and is what you lean on for POSIX /bin/sh portability.

When comparisons get subtle, read the dedicated comparison articles linked above instead of duplicating every operator here.

Combining conditions with && and ||

Inside [[ you can combine tests:

n=3
if [[ "$n" -ge 1 && "$n" -le 5 ]]; then
  echo "in range"
fi

Output:

in range

Keep tests short; for long predicates, assign sub-results to variables or use early return/continue in functions and loops.

Nested if

Nothing special syntactically—just another if inside the then (or else) of an outer if:

n=7
if [[ -n "$n" ]]; then
  if [[ "$n" -gt 0 ]]; then
    echo "positive"
  else
    echo "non-positive"
  fi
else
  echo "empty input"
fi

Output:

positive

Same structure with n=-1:

n=-1
if [[ -n "$n" ]]; then
  if [[ "$n" -gt 0 ]]; then
    echo "positive"
  else
    echo "non-positive"
  fi
else
  echo "empty input"
fi

Output:

non-positive

Practical habits and pitfalls

• Quote variables in tests: [[ "$var" = foo ]] avoids word-splitting surprises.
• Do not trust $? immediately after echo inside the same branch if you meant the condition’s status—echo overwrites $?.
• Prefer [[ for Bash-only scripts; use [ when sh compatibility matters.
• elif is not else if—only one if/fi pair wraps the whole chain.

Summary

Bash if then else is just exit-code branching: if list; then … elif list; then … else … fi, where each list is usually [[ … ]], [ … ], or a command. Else if bash is written elif. Put broader checks after stricter ones so the right branch runs, quote expansions, and reach for [[ in Bash while remembering [ for portable scripts. With that, if else in bash shell scripts stay readable and predictable.

Further reading:

• GNU Bash manual — Conditional constructs