How do you create and assign variables in Bash?

Assign with name=value and absolutely no spaces around the = — name=42, not name = 42.

The no-spaces rule is the #1 beginner trap, and it exists because of how bash parses a line: it splits on spaces first. With spaces, name = value looks like the command name with arguments = and value, so bash tries to run a program called name. name=value (no spaces) is the only thing bash recognizes as an assignment.

name=value          # correct
message="Hello World"   # quote values containing spaces

name = value        # WRONG: runs command 'name'
name =value         # WRONG: runs 'name' with arg '=value'
name= value         # WRONG: sets name empty, then runs 'value'

Variable naming rules:

• Start with letter or underscore
• Can contain letters, numbers, underscores
• Case-sensitive (Name ≠ name)
• Convention: lowercase for local, UPPERCASE for exported

Examples:

# Simple assignment
greeting="Hello"
count=42

# With spaces - MUST quote
message="Hello World"

# From command output
today=$(date +%Y-%m-%d)
files=$(ls *.txt)

Tip: Always quote values containing spaces or special characters.