dotenvx run - Interpolation Syntax Summary (Variable Expansion, Default/Alternate Values)

# .env
DEFINED_VAR=hello
EMPTY_VAR=
# UNDEFINED_VAR is not set

# Default value syntax - use variable if set/non-empty, otherwise use default
TEST1=${DEFINED_VAR:-fallback}     # Result: "hello"
TEST2=${EMPTY_VAR:-fallback}       # Result: "fallback"
TEST3=${UNDEFINED_VAR:-fallback}   # Result: "fallback"

# Default value syntax (no colon) - use variable if set, otherwise use default
TEST4=${DEFINED_VAR-fallback}      # Result: "hello"
TEST5=${EMPTY_VAR-fallback}        # Result: "" (empty, but set)
TEST6=${UNDEFINED_VAR-fallback}    # Result: "fallback"

# Alternate value syntax - use alternate if variable is set/non-empty, otherwise empty
TEST7=${DEFINED_VAR:+alternate}    # Result: "alternate"
TEST8=${EMPTY_VAR:+alternate}      # Result: "" (empty)
TEST9=${UNDEFINED_VAR:+alternate}  # Result: "" (empty)

# Alternate value syntax (no colon) - use alternate if variable is set, otherwise empty
TEST10=${DEFINED_VAR+alternate}    # Result: "alternate"
TEST11=${EMPTY_VAR+alternate}      # Result: "alternate" (empty but set)
TEST12=${UNDEFINED_VAR+alternate}  # Result: "" (empty)